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AuthorTitleYearJournal/ProceedingsReftypeDOI/URL
Thanwerdas, J., Berchet, A., Constantin, L., Tsuruta, A., Steiner, M., Reum, F., Henne, S. and Brunner, D. Improving the ensemble square root filter (EnSRF) in the Community
Inversion Framework: a case study with ICON-ART 2024.01
2025 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 18(5), pp. 1505-1544 
article DOI  
Abstract: The Community Inversion Framework (CIF) brings together methods for
estimating greenhouse gas fluxes from atmospheric observations. While
the analytical and variational optimization methods implemented in CIF
are operational and have proved to be accurate and efficient, the
initial ensemble method was found to be incomplete and could hardly be
compared to other ensemble methods employed in the inversion community,
mainly owing to strong performance limitations and absence of
localization methods. In this paper, we present and evaluate a new
implementation of the ensemble mode, building upon the initial
developments. As a first step, we chose to implement the serial and
batch versions of the ensemble square root filter (EnSRF) algorithm
because it is widely employed in the inversion community. We provide a
comprehensive description of the technical implementation in CIF and the
useful features it can provide to users. Finally, we demonstrate the
capabilities of the CIF-EnSRF system using a large number of synthetic
experiments over Europe with the flexible and scalable high-performance
atmospheric transport model ICON-ART, exploring the system's sensitivity
to multiple parameters that can be tuned by users. As expected, the
results are sensitive to the ensemble size and localization parameters.
Other tested parameters, such as the number of lags, the propagation
factors, or the localization function, can also have a substantial
influence on the results. We also introduce and provide a way of
interpreting a set of metrics that are automatically computed by CIF and
that can help assess the success of inversions and compare them. This
work complements previous efforts focused on other inversion methods
within CIF. While ICON-ART has been used for testing in this work, the
integration of these new ensemble algorithms enables any atmospheric
transport model to perform inversions, fully leveraging CIF's robust
capabilities.
BibTeX:
@article{WOS:001440421000001,
  author = {Thanwerdas, Joel and Berchet, Antoine and Constantin, Lionel and
Tsuruta, Aki and Steiner, Michael and Reum, Friedemann and Henne,
Stephan and Brunner, Dominik}, title = {Improving the ensemble square root filter (EnSRF) in the Community
Inversion Framework: a case study with ICON-ART 2024.01}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2025}, volume = {18}, number = {5}, pages = {1505-1544}, doi = {https://doi.org/10.5194/gmd-18-1505-2025} }
Tenkanen, M.K., Tsuruta, A., Denier van der Gon, H., Hoglund-Isaksson, L., Leppanen, A., Markkanen, T., Petrescu, A.M.R., Raivonen, M., Aaltonen, H. and Aalto, T. Partitioning anthropogenic and natural methane emissions in Finland
during 2000-2021 by combining bottom-up and top-down estimates
2025 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 25(4), pp. 2181-2206 
article DOI  
Abstract: Accurate national methane (CH4) emission estimates are essential for
tracking progress towards climate goals. This study investigated Finnish
CH4 emissions from 2000-2021 using bottom-up and top-down approaches. We
evaluated the ability of a global atmospheric inverse model
CarbonTracker Europe - CH4 to estimate CH4 emissions within a single
country. We focused on how different priors and their uncertainties
affect the optimised emissions and showed that the optimised
anthropogenic and natural CH4 emissions were strongly dependent on the
prior emissions. However, while the range of CH4 estimates was large,
the optimised emissions were more constrained than the bottom-up
estimates. Further analysis showed that the optimisation aligned the
trends of anthropogenic and natural CH4 emissions and improved the
modelled seasonal cycles of natural emissions. Comparison of atmospheric
CH4 observations with model results showed no clear preference between
anthropogenic inventories (EDGAR v6 and CAMS-REG), but results using the
highest natural prior (JSBACH-HIMMELI) agreed best with observations,
suggesting that process-based models may underestimate CH4 emissions
from Finnish peatlands or unaccounted sources such as freshwater
emissions. Additionally, using an uncertainty estimate based on a
process-based model ensemble for natural CH4 emissions seemed to be
advantageous compared to the standard uncertainty definition. The
average total posterior emission of the ensemble from one inverse model
with different priors was similar to the average of the ensemble
including different inverse models but similar priors. Thus, a single
inverse model using a range of priors can be used to reliably estimate
CH4 emissions when an ensemble of different models is unavailable.
BibTeX:
@article{WOS:001424715700001,
  author = {Tenkanen, Maria K. and Tsuruta, Aki and Denier van der Gon, Hugo and
Hoglund-Isaksson, Lena and Leppanen, Antti and Markkanen, Tiina and
Petrescu, Ana Maria Roxana and Raivonen, Maarit and Aaltonen, Hermanni
and Aalto, Tuula}, title = {Partitioning anthropogenic and natural methane emissions in Finland
during 2000-2021 by combining bottom-up and top-down estimates}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2025}, volume = {25}, number = {4}, pages = {2181-2206}, doi = {https://doi.org/10.5194/acp-25-2181-2025} }
Parmentier, F.-J.W., Thornton, B.F., Silyakova, A. and Christensen, T.R. Vulnerability of Arctic-Boreal methane emissions to climate change 2024 FRONTIERS IN ENVIRONMENTAL SCIENCE
Vol. 12 
article DOI  
Abstract: The rapid warming of the Arctic-Boreal region has led to the concern
that large amounts of methane may be released to the atmosphere from its
carbon-rich soils, as well as subsea permafrost, amplifying climate
change. In this review, we assess the various sources and sinks of
methane from northern high latitudes, in particular those that may be
enhanced by permafrost thaw. The largest terrestrial sources of the
Arctic-Boreal region are its numerous wetlands, lakes, rivers and
streams. However, fires, geological seeps and glacial margins can be
locally strong emitters. In addition, dry upland soils are an important
sink of atmospheric methane. We estimate that the net emission of all
these landforms and point sources may be as much as 48.7 [13.3-86.9]
Tg CH4 yr-1. The Arctic Ocean is also a net source of methane to the
atmosphere, in particular its shallow shelves, but we assess that the
marine environment emits a fraction of what is released from the
terrestrial domain: 4.9 [0.4-19.4] Tg CH4 yr-1. While it appears
unlikely that emissions from the ocean surface to the atmosphere are
increasing, now or in the foreseeable future, evidence points towards a
modest increase from terrestrial sources over the past decades, in
particular wetlands and possibly lakes. The influence of permafrost thaw
on future methane emissions may be strongest through associated changes
in the hydrology of the landscape rather than the availability of
previously frozen carbon. Although high latitude methane sources are not
yet acting as a strong climate feedback, they might play an increasingly
important role in the net greenhouse gas balance of the Arctic-Boreal
region with continued climate change.
BibTeX:
@article{WOS:001359817000001,
  author = {Parmentier, Frans-Jan W. and Thornton, Brett F. and Silyakova, Anna and
Christensen, Torben R.}, title = {Vulnerability of Arctic-Boreal methane emissions to climate change}, journal = {FRONTIERS IN ENVIRONMENTAL SCIENCE}, year = {2024}, volume = {12}, doi = {https://doi.org/10.3389/fenvs.2024.1460155} }
Dils, B., Zhou, M., Camy-Peyret, C., De Maziere, M., Kangah, Y., Langerock, B., Prunet, P., Serio, C., Siddans, R. and Kerridge, B. Independent validation of IASI/MetOp-A LMD and RAL CH4
products using CAMS model, in situ profiles, and ground-based FTIR
measurements
2024 ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. 17(18), pp. 5491-5524 
article DOI  
Abstract: In this study, we carried out an independent validation of two methane
retrieval algorithms using spectra from the Infrared Atmospheric
Sounding Interferometer (IASI) that has been aboard the Meteorological
Operational Satellite A (MetOp-A) since 2006. Both algorithms, one
developed by the Laboratoire de M & eacute;t & eacute;orologie
Dynamique (LMD), called the non-linear inference scheme (NLISv8.3), and
the other by the Rutherford Appleton Laboratory (RAL), referred to as
RALv2.0, provide long-term global CH4 concentrations using distinctively
different retrieval approaches (neural network vs. optimal estimation,
respectively). They also differ with respect to the vertical range
covered, where LMD provides mid-tropospheric dry-air mole fractions
(mtCH(4)), and RAL provides mixing ratio profiles from which we can
derive total column-averaged dry-air mole fractions (XCH4) and
potentially two partial column layers (qCH(4)). We compared both CH4
products using the Copernicus Atmospheric Monitoring Service (CAMS)
model, in situ profiles (range extended using CAMS model data), and
ground-based Fourier transform infrared (FTIR) remote-sensing
measurements. The average difference (in mtCH(4)) with respect to in
situ profiles for LMD ranges between -0.3 and 10.9 ppb, while for RAL
the XCH(4 )difference ranges between -4.6 and -1.6 ppb. The standard
deviation (SD) of the observed differences between in situ measurements
and RAL retrievals is 14.1-21.9 ppb, which is consistently smaller than
that between LMD retrievals and in situ measurements (15.2-30.6 ppb). By
comparing with ground-based FTIR sites, the mean differences are within
+/- 10 ppb for both RAL and LMD retrievals. However, the SD of the
differences at the ground-based FTIR stations shows significantly lower
values for RAL (11-15 ppb) than for LMD (about 25 ppb). The long-term
trend and seasonal cycles of CH4 derived from the LMD and RAL products
are further investigated and discussed. The seasonal variation in XCH4
derived from RAL is consistent with the seasonal variation observed by
the ground-based FTIR measurements. However, the overall 2007-2015 XCH4
trend derived from RAL measurements is underestimated, if not adjusted,
for an anomaly occurring on 16 May 2013 due to a L1 calibration change.
For LMD, we see very good agreement at the (sub)tropics (<35 degrees
N-35 degrees S) but notice deviations in the seasonal cycle (both in the
amplitude and phase) and an underestimation of the long-term trend with
respect to the RAL and reference data at higher-latitude sites.
BibTeX:
@article{WOS:001313838100001,
  author = {Dils, Bart and Zhou, Minqiang and Camy-Peyret, Claude and De Maziere,
Martine and Kangah, Yannick and Langerock, Bavo and Prunet, Pascal and
Serio, Carmine and Siddans, Richard and Kerridge, Brian}, title = {Independent validation of IASI/MetOp-A LMD and RAL CH4
products using CAMS model, in situ profiles, and ground-based FTIR
measurements}, journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES}, year = {2024}, volume = {17}, number = {18}, pages = {5491-5524}, doi = {https://doi.org/10.5194/amt-17-5491-2024} }
Zhao, M., Tian, X., Wang, Y., Wang, X., Ciais, P., Jin, Z., Zhang, H., Wang, T., Ding, J. and Piao, S. Slowdown in China's methane emission growth 2024 NATIONAL SCIENCE REVIEW
Vol. 11(8) 
article DOI  
Abstract: The unprecedented surge in global methane levels has raised global
concerns in recent years, casting a spotlight on China as a pivotal
emitter. China has taken several actions to curb the methane emissions,
but their effects remain unclear. Here, we developed the Global
ObservatioN-based system for monitoring Greenhouse GAses for methane
(GONGGA-CH4) and assimilate GOSAT XCH4 observations to assess changes in
China's methane emissions. We find the average rate of increase in
China's methane emissions (0.1 +/- 0.3 Tg CH4 yr-2) during 2016-2021
slowed down compared to the preceding years (2011-2015) (0.9 +/- 0.5 Tg
CH4 yr-2), in contrast to the concurrent acceleration of global methane
emissions. As a result, the contribution of China to global methane
emissions dropped significantly. Notably, the slowdown of China's
methane emission is mainly attributable to a reduction in biogenic
emissions from wetlands and agriculture, associated with the drying
trend in South China and the transition from double-season to
single-season rice cropping, while fossil fuel emissions are still
increasing. Our results suggest that GONGGA-CH4 provides the opportunity
for independent assessment of China's methane emissions from an
atmospheric perspective, providing insights into the implementation of
methane-related policies that align with its ambitious climate
objectives.
China's methane emission growth has slowed significantly due to reduced
emissions from agriculture and wetlands, with the Global
ObservatioN-based system for monitoring Greenhouse GAses for methane
(GONGGA-CH4) system providing crucial insights into these changes.
BibTeX:
@article{WOS:001310195100002,
  author = {Zhao, Min and Tian, Xiangjun and Wang, Yilong and Wang, Xuhui and Ciais,
Philippe and Jin, Zhe and Zhang, Hongqin and Wang, Tao and Ding, Jinzhi
and Piao, Shilong}, title = {Slowdown in China's methane emission growth}, journal = {NATIONAL SCIENCE REVIEW}, year = {2024}, volume = {11}, number = {8}, doi = {https://doi.org/10.1093/nsr/nwae223} }
Ishizawa, M., Chan, D., Worthy, D., Chan, E., Vogel, F., Melton, J.R. and Arora, V.K. Estimation of Canada's methane emissions: inverse modelling analysis
using the Environment and Climate Change Canada (ECCC) measurement
network
2024 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 24(17), pp. 10013-10038 
article DOI  
Abstract: Canada has major sources of atmospheric methane (CH4), with the world's
second-largest boreal wetland and the world's fourth-largest natural gas
production. However, Canada's CH4 emissions remain uncertain among
estimates. Better quantification and characterization of Canada's CH4
emissions are critical for climate mitigation strategies. To improve our
understanding of Canada's CH4 emissions, we performed an ensemble
regional inversion for 2007-2017 constrained with the Environment and
Climate Change Canada (ECCC) surface measurement network. The decadal
CH4 estimates show no significant trend, unlike some studies that
reported long-term trends. The total CH4 estimate is 17.4 (15.3-19.5)
TgCH4yr-1, partitioned into natural and anthropogenic sources at 10.8
(7.5-13.2) and 6.6 (6.2-7.8) TgCH4yr-1, respectively. The estimated
anthropogenic emission is higher than inventories, mainly in western
Canada (with the fossil fuel industry). Furthermore, the results reveal
notable spatiotemporal characteristics. First, the modelled differences
in atmospheric CH4 among the sites show improvement after inversion when
compared to observations, implying the CH4 observation differences could
help in verifying the inversion results. Second, the seasonal variations
show slow onset and a late-summer maximum, indicating wetland CH4 flux
has hysteretic dependence on air temperature. Third, the boreal winter
natural CH4 emissions, usually treated as negligible, appear
quantifiable (>= 20 % of annual emissions). Understanding winter
emission is important for climate prediction, as the winter in Canada is
warming faster than the summer. Fourth, the inter-annual variability in
estimated CH4 emissions is positively correlated with summer air
temperature anomalies. This could enhance Canada's natural CH4 emission
in the warming climate.
BibTeX:
@article{WOS:001308447600001,
  author = {Ishizawa, Misa and Chan, Douglas and Worthy, Doug and Chan, Elton and
Vogel, Felix and Melton, Joe R. and Arora, Vivek K.}, title = {Estimation of Canada's methane emissions: inverse modelling analysis
using the Environment and Climate Change Canada (ECCC) measurement
network}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2024}, volume = {24}, number = {17}, pages = {10013-10038}, doi = {https://doi.org/10.5194/acp-24-10013-2024} }
Zhang, Q., Wang, T., Wu, H., Qu, Y., Xie, M., Li, S., Zhuang, B., Li, M. and Kilifarska, N.A. Radiative and Chemical Effects of Non-Homogeneous Methane on Terrestrial
Carbon Fluxes in Asia
2024 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 129(8) 
article DOI  
Abstract: Methane (CH4) plays a crucial role in shaping terrestrial ecosystems due
to its radiative effect and atmospheric photochemical reactions. In this
study, we employed an enhanced regional climate-chemistry-ecosystem
model (RegCM-Chem-YIBs) to comprehensively evaluate the impacts of both
radiative and chemical effects of CH4 on terrestrial carbon fluxes
across the East, South, and Southeast Asia (EA, SA, SEA) during the year
2010. Our findings showed that the radiative effects of CH4 yielded a
positive influence on carbon fluxes. Specifically, the EA region
experienced a significant increase in the gross primary production
(GPP), reaching up to 0.515 Pg C Yr-1. In comparison, the SEA region
exhibited a decrease in the net ecosystem exchange (NEE) of
approximately -0.066 Pg C Yr-1. Further analysis revealed that
alterations in radiation and vapor pressure deficit (VPD) were dominant
drivers. Conversely, the chemical effects of CH4 lead to heightened
regional surface ozone (O3) concentrations (2.704-3.115 ppb) and
generate a negative response in carbon fluxes. Within the SEA region,
GPP observed a decrease of up to -0.144 Pg C Yr-1, while NEE displayed a
significant increase of 0.022 Pg C Yr-1. Taken together, the combined
radiative and chemical effects of CH4 indicated a positive impact on
regional carbon fluxes, with GPP increasing by 0.632 Pg C Yr-1 and NEE
decreasing by -0.09 Pg C Yr-1. This holistic perspective is crucial for
comprehending the intricate interactions linking climate change,
atmospheric pollution, and the global carbon cycle.
As the second-largest greenhouse gas in our atmosphere, methane (CH4) is
significantly influenced by human activities, and its emission sources
are extensively distributed across East, South, and Southeast Asia (EA,
SA, SEA). Moreover, the radiative and chemical effects of CH4 in the
atmosphere have far-reaching implications for terrestrial carbon fluxes.
Our research demonstrates that the radiative effects of CH4 have a
positive influence on terrestrial carbon fluxes, primarily driven by
variations in radiation and vapor pressure deficit (VPD). Conversely,
the chemical effects of CH4 result in increased regional surface ozone
(O3) concentrations, negatively affecting terrestrial carbon fluxes.
Overall, the total impact of CH4 is positive on regional terrestrial
ecosystem carbon fluxes, leading to a rise in Gross Primary Productivity
(GPP) by 0.632 Pg C Yr-1 and a reduction in net ecosystem exchangeby
-0.09 Pg C Yr-1. Our comprehensive study encompasses both radiative and
chemical aspects of CH4, providing a quantified evaluation of their
distinct influences on terrestrial carbon fluxes. This research lays a
critical scientific foundation for developing policies to mitigate
methane emissions.
The improved model accurately captures atmospheric methane's
spatiotemporal patterns, significantly influencing meteorology and
radiation Radiative effects of methane enhance terrestrial carbon
fluxes, mainly influenced by alterations in radiation and vapor pressure
deficit Chemical effects of methane amplify ozone production, which
negatively affects terrestrial carbon fluxes but exhibits less influence
BibTeX:
@article{WOS:001200535200001,
  author = {Zhang, Qian and Wang, Tijian and Wu, Hao and Qu, Yawei and Xie, Min and
Li, Shu and Zhuang, Bingliang and Li, Mengmeng and Kilifarska, Natalya
Andreeva}, title = {Radiative and Chemical Effects of Non-Homogeneous Methane on Terrestrial
Carbon Fluxes in Asia}, journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, year = {2024}, volume = {129}, number = {8}, doi = {https://doi.org/10.1029/2023JD040204} }
Chandra, N., Patra, P.K., Fujita, R., Hoeglund-Isaksson, L., Umezawa, T., Goto, D., Morimoto, S., Vaughn, B.H. and Rockmann, T. Methane emissions decreased in fossil fuel exploitation and sustainably
increased in microbial source sectors during 1990-2020
2024 COMMUNICATIONS EARTH &amp; ENVIRONMENT
Vol. 5(1) 
article DOI  
Abstract: Methane (CH4) emission reduction to limit warming to 1.5 degrees C can
be tracked by analyzing CH4 concentration and its isotopic composition
(delta 13C, delta D) simultaneously. Based on reconstructions of the
temporal trends, latitudinal, and vertical gradient of CH4 and delta 13C
from 1985 to 2020 using an atmospheric chemistry transport model, we
show (1) emission reductions from oil and gas exploitation (ONG) since
the 1990s stabilized the atmospheric CH4 growth rate in the late 1990s
and early 2000s, and (2) emissions from farmed animals, waste
management, and coal mining contributed to the increase in CH4 since
2006. Our findings support neither the increasing ONG emissions reported
by the EDGARv6 inventory during 1990-2020 nor the large unconventional
emissions increase reported by the GAINSv4 inventory since 2006. Total
fossil fuel emissions remained stable from 2000 to 2020, most likely
because the decrease in ONG emissions in some regions offset the
increase in coal mining emissions in China.
Methane emissions from agriculture and waste increased between 1990 and
2020 while fossil fuel emissions decreased until 2004 and subsequently
stabilised, suggest isotopic observations of methane emissions and
atmospheric chemistry modelling.
BibTeX:
@article{WOS:001205159300001,
  author = {Chandra, Naveen and Patra, Prabir K. and Fujita, Ryo and
Hoeglund-Isaksson, Lena and Umezawa, Taku and Goto, Daisuke and
Morimoto, Shinji and Vaughn, Bruce H. and Rockmann, Thomas}, title = {Methane emissions decreased in fossil fuel exploitation and sustainably
increased in microbial source sectors during 1990-2020}, journal = {COMMUNICATIONS EARTH &amp; ENVIRONMENT}, year = {2024}, volume = {5}, number = {1}, doi = {https://doi.org/10.1038/s43247-024-01286-x} }
Mahura, A., Baklanov, A., Makkonen, R., Boy, M., Petaja, T., Lappalainen, H.K., Nuterman, R., Kerminen, V.-M., Arnold, S.R., Jochum, M., Shvidenko, A., Esau, I., Sofiev, M., Stohl, A., Aalto, T., Bai, J., Chen, C., Cheng, Y., Drofa, O., Huang, M., Jarvi, L., Kokkola, H., Kouznetsov, R., Li, T., Malguzzi, P., Monks, S., Poulsen, M.B., Noe, S.M., Palamarchuk, Y., Foreback, B., Clusius, P., Rasmussen, T.A.S., She, J., Sorensen, J.H., Spracklen, D., Su, H., Tonttila, J., Wang, S., Wang, J., Wolf-Grosse, T., Yu, Y., Zhang, Q., Zhang, W., Zhang, W., Zheng, X., Li, S., Li, Y., Zhou, P. and Kulmala, M. Towards seamless environmental prediction - development of Pan-Eurasian
EXperiment (PEEX) modelling platform
2024 BIG EARTH DATA
Vol. 8(2, SI), pp. 189-230 
article DOI  
Abstract: The Pan-Eurasian Experiment Modelling Platform (PEEX-MP) is one of the
key blocks of the PEEX Research Programme. The PEEX MP has more than 30
models and is directed towards seamless environmental prediction. The
main focus area is the Arctic-boreal regions and China. The models used
in PEEX-MP cover several main components of the Earth's system, such as
the atmosphere, hydrosphere, pedosphere and biosphere, and resolve the
physical-chemical-biological processes at different spatial and temporal
scales and resolutions. This paper introduces and discusses PEEX MP
multi-scale modelling concept for the Earth system, online integrated,
forward/inverse, and socioeconomical modelling, and other approaches
with a particular focus on applications in the PEEX geographical domain.
The employed high-performance computing facilities, capabilities, and
PEEX dataflow for modelling results are described. Several virtual
research platforms (PEEX-View, Virtual Research Environment, Web-based
Atlas) for handling PEEX modelling and observational results are
introduced. The overall approach allows us to understand better
physical-chemical-biological processes, Earth's system interactions and
feedbacks and to provide valuable information for assessment studies on
evaluating risks, impact, consequences, etc. for population, environment
and climate in the PEEX domain. This work was also one of the last
projects of Prof. Sergej Zilitinkevich, who passed away on 15 February
2021. Since the finalization took time, the paper was actually submitted
in 2023 and we could not argue that the final paper text was agreed with
him.
BibTeX:
@article{WOS:001199315700001,
  author = {Mahura, Alexander and Baklanov, Alexander and Makkonen, Risto and Boy,
Michael and Petaja, Tuukka and Lappalainen, Hanna K. and Nuterman, Roman
and Kerminen, Veli-Matti and Arnold, Stephen R. and Jochum, Markus and
Shvidenko, Anatoly and Esau, Igor and Sofiev, Mikhail and Stohl, Andreas
and Aalto, Tuula and Bai, Jianhui and Chen, Chuchu and Cheng, Yafang and
Drofa, Oxana and Huang, Mei and Jarvi, Leena and Kokkola, Harri and
Kouznetsov, Rostislav and Li, Tingting and Malguzzi, Piero and Monks,
Sarah and Poulsen, Mads Bruun and Noe, Steffen M. and Palamarchuk,
Yuliia and Foreback, Benjamin and Clusius, Petri and Rasmussen, Till
Andreas Soya and She, Jun and Sorensen, Jens Havskov and Spracklen,
Dominick and Su, Hang and Tonttila, Juha and Wang, Siwen and Wang,
Jiandong and Wolf-Grosse, Tobias and Yu, Yongqiang and Zhang, Qing and
Zhang, Wei and Zhang, Wen and Zheng, Xunhua and Li, Siqi and Li, Yong
and Zhou, Putian and Kulmala, Markku}, title = {Towards seamless environmental prediction - development of Pan-Eurasian
EXperiment (PEEX) modelling platform}, journal = {BIG EARTH DATA}, year = {2024}, volume = {8}, number = {2, SI}, pages = {189-230}, doi = {https://doi.org/10.1080/20964471.2024.2325019} }
Miner, K.R., Braghiere, R.K., Miller, C.E., Schlegel, N. and Schimel, D. A Decadal Survey Without Analogs: Earth Observation Needs for a Warming
World
2024 AGU ADVANCES
Vol. 5(2) 
article DOI  
Abstract: Since 2007, the National Academy for Sciences Engineering and Medicine
(NASEM) has recommended Earth Science research and investment priorities
every 10 years. The Decadal Survey balances the continuation of
essential climate variable time series against unmet measurement needs
and new Earth Observations made possible by technological breakthroughs.
The next survey (2027-2028, DS28) will be framed by a rapidly changing
world, and it will be critical to anticipate the observational needs of
the 2030s-2040s, a world increasingly dominated by climate extremes and
a rapidly changing Earth system. Here, we highlight some of the changes
that factor into a framework for the DS28. Plain Language Summary Here,
we highlight some of the Earth system changes in the 2030-2050 period
that factor into a framework for the DS28.
BibTeX:
@article{WOS:001188078000001,
  author = {Miner, K. R. and Braghiere, R. K. and Miller, C. E. and Schlegel, N. and
Schimel, D.}, title = {A Decadal Survey Without Analogs: Earth Observation Needs for a Warming
World}, journal = {AGU ADVANCES}, year = {2024}, volume = {5}, number = {2}, doi = {https://doi.org/10.1029/2023AV001148} }
Khaliq, M.A., Mustafa, F., Rehman, S.U., Shahzaman, M., Javed, Z., Sagir, M., Bashir, S. and Zuo, H. Spatiotemporal investigation of near-surface CH4 and factors influencing
CH4 over South, East, and Southeast Asia
2024 SCIENCE OF THE TOTAL ENVIRONMENT
Vol. 922 
article DOI  
Abstract: Methane (CH4) is the second most abundant greenhouse gas after CO2,
which plays the most important role in global and regional climate
change. To explore the long-term spatiotemporal variations of
near-surface CH4, datasets were extracted from Greenhouse gases
Observing SATellite (GOSAT), and the Copernicus Atmospheric Monitoring
Service (CAMS) reanalyzed datasets from June 2009 to September 2020 over
South, East, and Southeast Asia. The accuracy of near-surface CH4 from
GOSAT and CAMS was verified against surface observatory stations
available in the study region to confirm both dataset applicability and
results showed significant correlations. Temporal plots revealed
continuous inflation in the near-surface CH4 with a significant seasonal
and monthly variation in the study region. To explore the factors
affecting near-surface CH4 distribution, near-surface CH4 relationship
with anthropogenic emission, NDVI data, wind speed, temperature,
precipitation, soil moisture, and relative humidity were investigated.
The results showed a significant contribution of anthropogenic emissions
with near-surface CH4. Regression and correlation analysis showed a
significant positive correlation between NDVI data and near -surface CH4
from GOSAT and CAMS, while a significant negative correlation was found
between wind and near -surface CH4. In the case of temperature, soil
moisture, and near -surface CH4 from GOSAT and CAMS over high CH4
regions of the study area showed a significant positive correlation.
However significant negative correlations were found between
precipitation and relative humidity with GOSAT and CAMS datasets over
high CH4 regions in South, East, and Southeast Asia. Moreover, these
climatic factors showed no significant correlation within the low near
-surface CH4 areas in our study region. Our study results showed that
anthropogenic emissions, NDVI data, wind speed, temperature,
precipitation, soil moisture, and humidity could significantly affect
the near -surface CH4 over South, East, and Southeast Asia.
BibTeX:
@article{WOS:001210938400001,
  author = {Khaliq, Muhammad Athar and Mustafa, Farhan and Rehman, Shafeeq Ur and
Shahzaman, Muhammad and Javed, Zeeshan and Sagir, Muhammad and Bashir,
Safdar and Zuo, Hongchao}, title = {Spatiotemporal investigation of near-surface CH4 and factors influencing
CH4 over South, East, and Southeast Asia}, journal = {SCIENCE OF THE TOTAL ENVIRONMENT}, year = {2024}, volume = {922}, doi = {https://doi.org/10.1016/j.scitotenv.2024.171311} }
Steiner, M., Peters, W., Luijkx, I., Henne, S., Chen, H., Hammer, S. and Brunner, D. European CH4 inversions with ICON-ART coupled to the CarbonTracker Data
Assimilation Shell
2024 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 24(4), pp. 2759-2782 
article DOI  
Abstract: We present the first application of the ICOsahedral Nonhydrostatic model
with Aerosols and Reactive Trace gases (ICON-ART) in inverse modeling in
inverse modeling of greenhouse gas fluxes with an ensemble Kalman
smoother. For this purpose, we extended ICON-ART to efficiently handle
gridded emissions, generate an ensemble of perturbed emissions during
runtime and use nudging on selected variables to keep the simulations
close to analyzed meteorology. We show that the system can optimize
total and anthropogenic European CH (4) fluxes on a national scale in an
idealized setup using pseudo-observations from a realistic network of
measurement stations. However, we were unable to constrain the sum of
the natural emission sources of comparatively low magnitude. Also
regions with low emissions and regions with low observational coverage
could not be optimized individually for lack of observational
constraints. Furthermore, we investigated the sensitivities towards
different inversion parameters and design choices with 15 sensitivity
runs using the same idealized setup, demonstrating the robustness of the
approach when regarding some minimal requirements of the setup (e.g.,
number of ensemble members). Subsequently, we applied the system to real
in situ observations from 28 European stations for three years, 2008,
2013 and 2018. We used a priori anthropogenic fluxes from the EDGARv6
inventory and a priori natural fluxes from peatlands and mineral soils,
inland waters, the ocean, biofuels and biomass burning, and geology. Our
results for the year 2018 indicate that anthropogenic emissions may be
underestimated in EDGARv6 by ca. 25 % in the Benelux countries and, to
a smaller degree, in northwestern France and southern England. In the
rest of the domain, anthropogenic fluxes are corrected downwards by the
inversion, suggesting an overestimation in the a priori. For most
countries, this means that the a posteriori country-total anthropogenic
emissions are closer to the values reported to the United Nations
Framework Convention on Climate Change (UNFCCC) than the a priori
emissions from EDGARv6. Aggregating the a posteriori emissions across
the EU27 + UK results in a total of 17.4 Tg yr( - 1) , while the a
priori emissions were 19.9 Tg yr( - 1 ). Our a posteriori is close to
the total reported to the UNFCCC of 17.8 Tg yr (- 1 ). Natural emissions
are reduced from their a priori magnitude almost everywhere, especially
over Italy and Romania-Moldova, where a priori geological emissions are
high, and over the United Kingdom and Scandinavia, where emissions from
peatlands and wetlands were possibly unusually low during the hot and
dry summer of 2018. Our a posteriori anthropogenic emissions for the
EU27 + UK fall within the range estimated by global top-down studies but
are lower than most other regional inversions. However, many of these
studies have used observations from different measurement stations or
satellite observations. The spatial pattern of the emission increments
in our results, especially the increase in the Benelux countries, also
agrees well with other regional inversions.
BibTeX:
@article{WOS:001190546100001,
  author = {Steiner, Michael and Peters, Wouter and Luijkx, Ingrid and Henne,
Stephan and Chen, Huilin and Hammer, Samuel and Brunner, Dominik}, title = {European CH4 inversions with ICON-ART coupled to the CarbonTracker Data
Assimilation Shell}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2024}, volume = {24}, number = {4}, pages = {2759-2782}, doi = {https://doi.org/10.5194/acp-24-2759-2024} }
Yuan, K., Li, F., McNicol, G., Chen, M., Hoyt, A., Knox, S., Riley, W.J., Jackson, R. and Zhu, Q. Boreal-Arctic wetland methane emissions modulated by warming and
vegetation activity
2024 NATURE CLIMATE CHANGE
Vol. 14(3) 
article DOI  
Abstract: Wetland methane (CH4) emissions over the Boreal-Arctic region are
vulnerable to climate change and linked to climate feedbacks, yet
understanding of their long-term dynamics remains uncertain. Here, we
upscaled and analysed two decades (2002-2021) of Boreal-Arctic wetland
CH4 emissions, representing an unprecedented compilation of eddy
covariance and chamber observations. We found a robust increasing trend
of CH4 emissions (+8.9%) with strong inter-annual variability. The
majority of emission increases occurred in early summer (June and July)
and were mainly driven by warming (52.3%) and ecosystem productivity
(40.7%). Moreover, a 2 degrees C temperature anomaly in 2016 led to the
highest recorded annual CH4 emissions (22.3 Tg CH4 yr-1) over this
region, driven primarily by high emissions over Western Siberian
lowlands. However, current-generation models from the Global Carbon
Project failed to capture the emission magnitude and trend, and may bias
the estimates in future wetland CH4 emission driven by amplified
Boreal-Arctic warming and greening.
Whether methane emissions from the Boreal-Arctic region are increasing
under climate change is unclear, but critical for determining climate
feedbacks. This study uses observations and machine learning to show an
increase in wetland methane emissions over the past two decades, with
inter-annual variation.
BibTeX:
@article{WOS:001162170300001,
  author = {Yuan, Kunxiaojia and Li, Fa and McNicol, Gavin and Chen, Min and Hoyt,
Alison and Knox, Sara and Riley, William J. and Jackson, Robert and Zhu,
Qing}, title = {Boreal-Arctic wetland methane emissions modulated by warming and
vegetation activity}, journal = {NATURE CLIMATE CHANGE}, year = {2024}, volume = {14}, number = {3}, doi = {https://doi.org/10.1038/s41558-024-01933-3} }
Wu, W., Liu, X., Xiong, X., Yang, Q., Zhou, L., Lei, L., Zhou, D.K. and Larar, A.M. Spectral Fingerprinting of Methane from Hyper-Spectral Sounder
Measurements Using Machine Learning and Radiative Kernel-Based Inversion
2024 REMOTE SENSING
Vol. 16(3) 
article DOI  
Abstract: Satellite-based hyper-spectral infrared (IR) sensors such as the
Atmospheric Infrared Sounder (AIRS), the Cross-track Infrared Sounder
(CrIS), and the Infrared Atmospheric Sounding Interferometer (IASI)
cover many methane (CH4) spectral features, including the nu 1
vibrational band near 1300 cm-1 (7.7 mu m); therefore, they can be used
to monitor CH4 concentrations in the atmosphere. However, retrieving CH4
remains a challenge due to the limited spectral information provided by
IR sounder measurements. The information required to resolve the weak
absorption lines of CH4 is often obscured by interferences from signals
originating from other trace gases, clouds, and surface emissions within
the overlapping spectral region. Consequently, currently available CH4
data product derived from IR sounder measurements still have large
errors and uncertainties that limit their application scope for
high-accuracy climate and environment monitoring applications. In this
paper, we describe the retrieval of atmospheric CH4 profiles using a
novel spectral fingerprinting methodology and our evaluation of
performance using measurements from the CrIS sensor aboard the Suomi
National Polar-orbiting Partnership (SNPP) satellite. The spectral
fingerprinting methodology uses optimized CrIS radiances to enhance the
CH4 signal and a machine learning classifier to constrain the physical
inversion scheme. We validated our results using the atmospheric
composition reanalysis results and data from airborne in situ
measurements. An inter-comparison study revealed that the spectral
fingerprinting results can capture the vertical variation
characteristics of CH4 profiles that operational sounder products may
not provide. The latitudinal variations in CH4 concentration in these
results appear more realistic than those shown in existing sounder
products. The methodology presented herein could enhance the utilization
of satellite data to comprehend methane's role as a greenhouse gas and
facilitate the tracking of methane sources and sinks with increased
reliability.
BibTeX:
@article{WOS:001161895000001,
  author = {Wu, Wan and Liu, Xu and Xiong, Xiaozhen and Yang, Qiguang and Zhou,
Lihang and Lei, Liqiao and Zhou, Daniel K. and Larar, Allen M.}, title = {Spectral Fingerprinting of Methane from Hyper-Spectral Sounder
Measurements Using Machine Learning and Radiative Kernel-Based Inversion}, journal = {REMOTE SENSING}, year = {2024}, volume = {16}, number = {3}, doi = {https://doi.org/10.3390/rs16030578} }
Tenkanen, M.K., Tsuruta, A., Tyystjaervi, V., Toermae, M., Autio, I., Haakana, M., Tuomainen, T., Leppaenen, A., Markkanen, T., Raivonen, M., Niinistoe, S., Arslan, A.N. and Aalto, T. Using Atmospheric Inverse Modelling of Methane Budgets with Copernicus
Land Water and Wetness Data to Detect Land Use-Related Emissions
2024 REMOTE SENSING
Vol. 16(1) 
article DOI  
Abstract: Climate change mitigation requires countries to report their annual
greenhouse gas (GHG) emissions and sinks, including those from land use,
land use change, and forestry (LULUCF). In Finland, the LULUCF sector
plays a crucial role in achieving net-zero GHG emissions, as the sector
is expected to be a net sink. However, accurate estimates of
LULUCF-related GHG emissions, such as methane (CH4), remain challenging.
We estimated LULUCF-related CH4 emissions in Finland in 2013-2020 by
combining national land cover and remote-sensed surface wetness data
with CH4 emissions estimated by an inversion model. According to our
inversion model, most of Finland's CH4 emissions were attributed to
natural sources such as open pristine peatlands. However, our research
indicated that forests with thin tree cover surrounding open peatlands
may also be a significant source of CH4. Unlike open pristine peatlands
and pristine peatlands with thin tree cover, surrounding transient
forests are included in the Finnish GHG inventory if they meet the
criteria used for forest land. The current Finnish national GHG
inventory may therefore underestimate CH4 emissions from forested
organic soils surrounding open peatlands, although more precise methods
and data are needed to verify this. Given the potential impact on net
GHG emissions, CH4 emissions from transitional forests on organic soils
should be further investigated. Furthermore, the results demonstrate the
potential of combining atmospheric inversion modelling of GHGs with
diverse data sources and highlight the need for methods to more easily
combine atmospheric inversions with national GHG inventories.
BibTeX:
@article{WOS:001140299900001,
  author = {Tenkanen, Maria K. and Tsuruta, Aki and Tyystjaervi, Vilna and Toermae,
Markus and Autio, Iida and Haakana, Markus and Tuomainen, Tarja and
Leppaenen, Antti and Markkanen, Tiina and Raivonen, Maarit and
Niinistoe, Sini and Arslan, Ali Nadir and Aalto, Tuula}, title = {Using Atmospheric Inverse Modelling of Methane Budgets with Copernicus
Land Water and Wetness Data to Detect Land Use-Related Emissions}, journal = {REMOTE SENSING}, year = {2024}, volume = {16}, number = {1}, doi = {https://doi.org/10.3390/rs16010124} }
McNicol, G., Fluet-Chouinard, E., Ouyang, Z., Knox, S., Zhang, Z., Aalto, T., Bansal, S., Chang, K.-Y., Chen, M., Delwiche, K., Feron, S., Goeckede, M., Liu, J., Malhotra, A., Melton, J.R., Riley, W., Vargas, R., Yuan, K., Ying, Q., Zhu, Q., Alekseychik, P., Aurela, M., Billesbach, D.P., Campbell, D.I., Chen, J., Chu, H., Desai, A.R., Euskirchen, E., Goodrich, J., Griffis, T., Helbig, M., Hirano, T., Iwata, H., Jurasinski, G., King, J., Koebsch, F., Kolka, R., Krauss, K., Lohila, A., Mammarella, I., Nilson, M., Noormets, A., Oechel, W., Peichl, M., Sachs, T., Sakabe, A., Schulze, C., Sonnentag, O., Sullivan, R.C., Tuittila, E.-S., Ueyama, M., Vesala, T., Ward, E., Wille, C., Wong, G.X., Zona, D., Windham-Myers, L., Poulter, B. and Jackson, R.B. Upscaling Wetland Methane Emissions From the FLUXNET-CH4 Eddy Covariance
Network (UpCH4 v1.0): Model Development, Network Assessment, and Budget
Comparison
2023 AGU ADVANCES
Vol. 4(5) 
article DOI  
Abstract: Wetlands are responsible for 20%-31% of global methane (CH4) emissions
and account for a large source of uncertainty in the global CH4 budget.
Data-driven upscaling of CH4 fluxes from eddy covariance measurements
can provide new and independent bottom-up estimates of wetland CH4
emissions. Here, we develop a six-predictor random forest upscaling
model (UpCH4), trained on 119 site-years of eddy covariance CH4 flux
data from 43 freshwater wetland sites in the FLUXNET-CH4 Community
Product. Network patterns in site-level annual means and mean seasonal
cycles of CH4 fluxes were reproduced accurately in tundra, boreal, and
temperate regions (Nash-Sutcliffe Efficiency similar to 0.52-0.63 and
0.53). UpCH(4) estimated annual global wetland CH4 emissions of 146 +/-
43 TgCH4 y(-1) for 2001-2018 which agrees closely with current bottom-up
land surface models (102-181 TgCH4 y(-1)) and overlaps with top-down
atmospheric inversion models (155-200 TgCH4 y -1). However, UpCH4
diverged from both types of models in the spatial pattern and seasonal
dynamics of tropical wetland emissions. We conclude that upscaling of
eddy covariance CH4 fluxes has the potential to produce realistic
extra-tropical wetland CH4 emissions estimates which will improve with
more flux data. To reduce uncertainty in upscaled estimates, researchers
could prioritize new wetland flux sites along humid-to-arid tropical
climate gradients, from major rainforest basins (Congo, Amazon, and SE
Asia), into monsoon (Bangladesh and India) and savannah regions (African
Sahel) and be paired with improved knowledge of wetland extent seasonal
dynamics in these regions. The monthly wetland methane products gridded
at 0.25 degrees from UpCH4 are available via ORNL DAAC
(https://doi.org/10.3334/ ORNLDAAC/2253).
Plain Language Summary Wetlands account for a large share of global
methane emissions to the atmosphere, but current estimates vary widely
in magnitude (similar to 30% uncertainty on annual global emissions)
and spatial distribution, with diverging predictions for tropical rice
growing (e.g., Bengal basin), rainforest (e.g., Amazon basin), and
floodplain savannah (e.g., Sudd) regions. Wetland methane model
estimates could be improved by increased use of land surface methane
flux data. Upscaling approaches use flux data collected across globally
distributed measurement networks in a machine learning framework to
extrapolate fluxes in space and time. Here, we train and evaluate a
methane upscaling model (UpCH4) and use it to generate monthly, globally
gridded wetland methane emissions estimates for 2001-2018. The UpCH4
model uses only six predictor variables among which temperature is
dominant. Global annual methane emissions estimates and associated
uncertainty ranges from upscaling fall within state-of-the-art model
ensemble estimates from the Global Carbon Project (GCP) methane budget.
In some tropical regions, the spatial pattern of UpCH4 emissions
diverged from GCP predictions, however, inclusion of flux measurements
from additional ground-based sites, together with refined maps of
tropical wetlands extent, could reduce these prediction uncertainties.
BibTeX:
@article{WOS:001065650800001,
  author = {McNicol, Gavin and Fluet-Chouinard, Etienne and Ouyang, Zutao and Knox,
Sara and Zhang, Zhen and Aalto, Tuula and Bansal, Sheel and Chang,
Kuang-Yu and Chen, Min and Delwiche, Kyle and Feron, Sarah and Goeckede,
Mathias and Liu, Jinxun and Malhotra, Avni and Melton, Joe R. and Riley,
William and Vargas, Rodrigo and Yuan, Kunxiaojia and Ying, Qing and Zhu,
Qing and Alekseychik, Pavel and Aurela, Mika and Billesbach, David P.
and Campbell, David I. and Chen, Jiquan and Chu, Housen and Desai, Ankur
R. and Euskirchen, Eugenie and Goodrich, Jordan and Griffis, Timothy and
Helbig, Manuel and Hirano, Takashi and Iwata, Hiroki and Jurasinski,
Gerald and King, John and Koebsch, Franziska and Kolka, Randall and
Krauss, Ken and Lohila, Annalea and Mammarella, Ivan and Nilson, Mats
and Noormets, Asko and Oechel, Walter and Peichl, Matthias and Sachs,
Torsten and Sakabe, Ayaka and Schulze, Christopher and Sonnentag, Oliver
and Sullivan, Ryan C. and Tuittila, Eeva-Stiina and Ueyama, Masahito and
Vesala, Timo and Ward, Eric and Wille, Christian and Wong, Guan Xhuan
and Zona, Donatella and Windham-Myers, Lisamarie and Poulter, Benjamin
and Jackson, Robert B.}, title = {Upscaling Wetland Methane Emissions From the FLUXNET-CH4 Eddy Covariance
Network (UpCH4 v1.0): Model Development, Network Assessment, and Budget
Comparison}, journal = {AGU ADVANCES}, year = {2023}, volume = {4}, number = {5}, doi = {https://doi.org/10.1029/2023AV000956} }
Pendergrass, D.C., Jacob, D.J., Nesser, H., Varon, D.J., Sulprizio, M., Miyazaki, K. and Bowman, K.W. CHEEREIO 1.0: a versatile and user-friendly ensemble-based chemical data
assimilation and emissions inversion platform for the GEOS-Chem chemical
transport model
2023 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 16(16), pp. 4793-4810 
article DOI  
Abstract: We present a versatile, powerful, and user-friendly chemical data
assimilation toolkit for simultaneously optimizing emissions and
concentrations of chemical species based on atmospheric observations
from satellites or suborbital platforms. The CHemistry and Emissions
REanalysis Interface with Observations (CHEEREIO) exploits the GEOS-Chem
chemical transport model and a localized ensemble transform Kalman
filter algorithm (LETKF) to determine the Bayesian optimal (posterior)
emissions and/or concentrations of a set of species based on
observations and prior information using an easy-to-modify configuration
file with minimal changes to the GEOS-Chem or LETKF code base. The LETKF
algorithm readily allows for nonlinear chemistry and produces
flow-dependent posterior error covariances from the ensemble simulation
spread. The object-oriented Python-based design of CHEEREIO allows users
to easily add new observation operators such as for satellites. CHEEREIO
takes advantage of the Harmonized Emissions Component (HEMCO) modular
structure of input data management in GEOS-Chem to update emissions from
the assimilation process independently from the GEOS-Chem code. It can
seamlessly support GEOS-Chem version updates and is adaptable to other
chemical transport models with similar modular input data structure. A
post-processing suite combines ensemble output into consolidated NetCDF
files and supports a wide variety of diagnostic data and visualizations.
We demonstrate CHEEREIO's capabilities with an out-of-the-box
application, assimilating global methane emissions and concentrations at
weekly temporal resolution and 2 circle x 2.5 circle spatial resolution
for 2019 using TROPOspheric Monitoring Instrument (TROPOMI) satellite
observations. CHEEREIO achieves a 50-fold improvement in computational
performance compared to the equivalent analytical inversion of TROPOMI
observations.
BibTeX:
@article{WOS:001168944600001,
  author = {Pendergrass, Drew C. and Jacob, Daniel J. and Nesser, Hannah and Varon,
Daniel J. and Sulprizio, Melissa and Miyazaki, Kazuyuki and Bowman,
Kevin W.}, title = {CHEEREIO 1.0: a versatile and user-friendly ensemble-based chemical data
assimilation and emissions inversion platform for the GEOS-Chem chemical
transport model}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2023}, volume = {16}, number = {16}, pages = {4793-4810}, doi = {https://doi.org/10.5194/gmd-16-4793-2023} }
Mannisenaho, V., Tsuruta, A., Backman, L., Houweling, S., Segers, A., Krol, M., Saunois, M., Poulter, B., Zhang, Z., Lan, X., Dlugokencky, E.J., Michel, S., White, J.W.C. and Aalto, T. Global Atmospheric δ13CH4 and CH4
Trends for 2000-2020 from the Atmospheric Transport Model TM5 Using
CH4 from Carbon Tracker Europe-CH4 Inversions
2023 ATMOSPHERE
Vol. 14(7) 
article DOI  
Abstract: This study investigates atmospheric delta(CH4)-C-13 trends, as produced
by a global atmospheric transport model using CH4 inversions from
CarbonTracker-Europe CH4 for 2000-2020, and compares them to
observations. The CH4 inversions include the grouping of the emissions
both by delta(CH4)-C-13 isotopic signatures and process type to
investigate the effect, and to estimate the CH4 magnitudes and model CH4
and delta(CH4)-C-13 trends. In addition to inversion results,
simulations of the global atmospheric transport model were performed
with modified emissions. The estimated global CH4 trends for oil and gas
were found to increase more than coal compared to the priors from
2000-2006 to 2007-2020. Estimated trends for coal emissions at 30
degrees N-60 degrees N are less than 50% of those from priors.
Estimated global CH4 rice emissions trends are opposite to priors, with
the largest contribution from the EQ to 60 degrees N. The results of
this study indicate that optimizing wetland emissions separately
produces better agreement with the observed delta(CH4)-C-13 trend than
optimizing all biogenic emissions simultaneously. This study recommends
optimizing separately biogenic emissions with similar isotopic signature
to wetland emissions. In addition, this study suggests that fossil-based
emissions were overestimated by 9% after 2012 and biogenic emissions
are underestimated by 8% in the inversion using EDGAR v6.0 as priors.
BibTeX:
@article{WOS:001039147700001,
  author = {Mannisenaho, Vilma and Tsuruta, Aki and Backman, Leif and Houweling,
Sander and Segers, Arjo and Krol, Maarten and Saunois, Marielle and
Poulter, Benjamin and Zhang, Zhen and Lan, Xin and Dlugokencky, Edward
J. and Michel, Sylvia and White, James W. C. and Aalto, Tuula}, title = {Global Atmospheric δ13CH4 and CH4
Trends for 2000-2020 from the Atmospheric Transport Model TM5 Using
CH4 from Carbon Tracker Europe-CH4 Inversions}, journal = {ATMOSPHERE}, year = {2023}, volume = {14}, number = {7}, doi = {https://doi.org/10.3390/atmos14071121} }
Song, H., Sheng, M., Lei, L., Guo, K., Zhang, S. and Ji, Z. Spatial and Temporal Variations of Atmospheric CH4 in Monsoon
Asia Detected by Satellite Observations of GOSAT and TROPOMI
2023 REMOTE SENSING
Vol. 15(13) 
article DOI  
Abstract: Space-based measurements, such as the Greenhouse gases Observing
SATellite (GOSAT) and the TROPOspheric Monitoring Instrument (TROPOMI)
aboard the Sentinel-5 Precursor satellite, provide global observations
of the column-averaged CH4 concentration (XCH4). Due to the irregular
observations and data gaps in the retrievals, studies on the spatial and
temporal variations of regional atmospheric CH4 concentrations are
limited. In this paper, we mapped XCH4 data over monsoon Asia using
GOSAT and TROPOMI observations from April 2009 to December 2021 and
analyzed the spatial and temporal pattern of atmospheric CH4 variations
and emissions. The results show that atmospheric CH4 concentrations over
monsoon Asia have long-term increases with an annual growth rate of
roughly 8.4 ppb. The spatial and temporal trends of XCH4 data are
significantly correlated with anthropogenic CH4 emissions from the
bottom-up emission inventory of EDGAR. The spatial pattern of gridded
XCH4 temporal variations in China presents a basically consistent
distribution with the Heihe-Tengchong Line, which is mainly related to
the difference in anthropogenic emissions in the eastern and western
areas. Using the mapping of XCH4 data from 2019 to 2021, this study
further revealed the response of atmospheric CH4 concentrations to
anthropogenic emissions in different urban agglomerations. For the urban
agglomerations, the triangle of Central China (TCC), the
Chengdu-Chongqing City Group (CCG), and the Yangtze River Delta (YRD)
show higher CH4 concentrations and emissions than the
Beijing-Tianjin-Hebei region and nearby areas (BTH). The results reveal
the spatial and temporal distribution of CH4 concentrations and quantify
the differences between urban agglomerations, which will support further
studies on the drivers of methane emissions.
BibTeX:
@article{WOS:001031094300001,
  author = {Song, Hao and Sheng, Mengya and Lei, Liping and Guo, Kaiyuan and Zhang,
Shaoqing and Ji, Zhanghui}, title = {Spatial and Temporal Variations of Atmospheric CH4 in Monsoon
Asia Detected by Satellite Observations of GOSAT and TROPOMI}, journal = {REMOTE SENSING}, year = {2023}, volume = {15}, number = {13}, doi = {https://doi.org/10.3390/rs15133389} }
Zhou, L., Warner, J., Nalli, N.R., Wei, Z., Oh, Y., Bruhwiler, L., Liu, X., Divakarla, M., Pryor, K., Kalluri, S. and Goldberg, M.D. Spatiotemporal Variability of Global Atmospheric Methane Observed from
Two Decades of Satellite Hyperspectral Infrared Sounders
2023 REMOTE SENSING
Vol. 15(12) 
article DOI  
Abstract: Methane (CH4) is the second most significant contributor to climate
change after carbon dioxide (CO2), accounting for approximately 20% of
the contributions from all well-mixed greenhouse gases. Understanding
the spatiotemporal distributions and the relevant long-term trends is
crucial to identifying the sources, sinks, and impacts on climate.
Hyperspectral thermal infrared (TIR) sounders, including the Atmospheric
Infrared Sounder (AIRS), the Cross-track Infrared Sounder (CrIS), and
the Infrared Atmospheric Sounding Interferometer (IASI), have been used
to measure global CH4 concentrations since 2002. This study analyzed
nearly 20 years of data from AIRS and CrIS and confirmed a significant
increase in CH4 concentrations in the mid-upper troposphere (around 400
hPa) from 2003 to 2020, with a total increase of approximately 85 ppb,
representing a +4.8% increase in 18 years. The rate of increase was
derived using global satellite TIR measurements, which are consistent
with in situ measurements, indicating a steady increase starting in 2007
and becoming stronger in 2014. The study also compared CH4
concentrations derived from the AIRS and CrIS against ground-based
measurements from NOAA Global Monitoring Laboratory (GML) and found
phase shifts in the seasonal cycles in the middle to high latitudes of
the northern hemisphere, which is attributed to the influence of
stratospheric CH4 that varies at different latitudes. These findings
provide insights into the global budget of atmospheric composition and
the understanding of satellite measurement sensitivity to CH4.
BibTeX:
@article{WOS:001018318900001,
  author = {Zhou, Lihang and Warner, Juying and Nalli, Nicholas R. and Wei, Zigang
and Oh, Youmi and Bruhwiler, Lori and Liu, Xingpin and Divakarla, Murty
and Pryor, Ken and Kalluri, Satya and Goldberg, Mitchell D.}, title = {Spatiotemporal Variability of Global Atmospheric Methane Observed from
Two Decades of Satellite Hyperspectral Infrared Sounders}, journal = {REMOTE SENSING}, year = {2023}, volume = {15}, number = {12}, doi = {https://doi.org/10.3390/rs15122992} }
Ludwig, S.M., Natali, S.M., Schade, J.D., Powell, M., Fiske, G., Schiferl, L.D. and Commane, R. Scaling waterbody carbon dioxide and methane fluxes in the arctic using
an integrated terrestrial-aquatic approach
2023 ENVIRONMENTAL RESEARCH LETTERS
Vol. 18(6) 
article DOI  
Abstract: In the Arctic waterbodies are abundant and rapid thaw of permafrost is
destabilizing the carbon cycle and changing hydrology. It is
particularly important to quantify and accurately scale aquatic carbon
emissions in arctic ecosystems. Recently available high-resolution
remote sensing datasets capture the physical characteristics of arctic
landscapes at unprecedented spatial resolution. We demonstrate how
machine learning models can capitalize on these spatial datasets to
greatly improve accuracy when scaling waterbody CO2 and CH4 fluxes
across the YK Delta of south-west AK. We found that waterbody size and
contour were strong predictors for aquatic CO2 emissions, attributing
greater than two-thirds of the influence to the scaling model. Small
ponds (<0.001 km(2)) were hotspots of emissions, contributing fluxes
several times their relative area, but were less than 5% of the total
carbon budget. Small to medium lakes (0.001-0.1 km(2)) contributed the
majority of carbon emissions from waterbodies. Waterbody CH4 emissions
were predicted by a combination of wetland landcover and related
drivers, as well as watershed hydrology, and waterbody surface
reflectance related to chromophoric dissolved organic matter. When
compared to our machine learning approach, traditional scaling methods
that did not account for relevant landscape characteristics
overestimated waterbody CO2 and CH4 emissions by 26%-79% and 8%-53%
respectively. This study demonstrates the importance of an integrated
terrestrial-aquatic approach to improving estimates and uncertainty when
scaling C emissions in the arctic.
BibTeX:
@article{WOS:000990896500001,
  author = {Ludwig, Sarah M. and Natali, Susan M. and Schade, John D. and Powell,
Margaret and Fiske, Greg and Schiferl, Luke D. and Commane, Roisin}, title = {Scaling waterbody carbon dioxide and methane fluxes in the arctic using
an integrated terrestrial-aquatic approach}, journal = {ENVIRONMENTAL RESEARCH LETTERS}, year = {2023}, volume = {18}, number = {6}, doi = {https://doi.org/10.1088/1748-9326/acd467} }
Bisht, J.S.H., Patra, P.K., Takigawa, M., Sekiya, T., Kanaya, Y., Saitoh, N. and Miyazaki, K. Estimation of CH4 emission based on an advanced 4D-LETKF
assimilation system
2023 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 16(6), pp. 1823-1838 
article DOI  
Abstract: Methane (CH4) is the second major greenhouse gas after carbon dioxide
(CO2) which has substantially increased during recent decades in the
atmosphere, raising serious sustainability and climate change issues.
Here, we develop a data assimilation system for in situ and
column-averaged concentrations using a local ensemble transform Kalman
filter (LETKF) to estimate surface emissions of CH4. The data
assimilation performance is tested and optimized based on idealized
settings using observation system simulation experiments (OSSEs), where
a known surface emission distribution (the truth) is retrieved from
synthetic observations. We tested three covariance inflation methods to
avoid covariance underestimation in the emission estimates, namely fixed
multiplicative (FM), relaxation-to-prior spread (RTPS), and adaptive
multiplicative. First, we assimilate the synthetic observations at every
grid point at the surface level. In such a case of dense observational
data, the normalized root mean square error (RMSE) in the analyses over
global land regions is smaller by 10 %-15 % in the case of RTPS
covariance inflation method compared to FM. We have shown that
integrated estimated flux seasonal cycles over 15 regions using RTPS
inflation are in reasonable agreement between true and estimated flux,
with 0.04 global normalized annual mean bias. We then assimilated the
column-averaged CH4 concentration by sampling the model simulations at
Greenhouse Gases Observing Satellite (GOSAT) observation locations and
time for another OSSE. Similar to the case of dense observational data,
the RTPS covariance inflation method performs better than FM for GOSAT
synthetic observation in terms of normalized RMSE (2 %-3 %) and
integrated flux estimation comparison with the true flux. The annual
mean averaged normalized RMSE (normalized mean bias) in LETKF CH4 flux
estimation in the case of RTPS and FM covariance inflation is found to
be 0.59 (0.18) and 0.61 (0.23), respectively. The ?(2) test performed
for GOSAT synthetic observations assimilation suggests high
underestimation of background error covariance in both RTPS and FM
covariance inflation methods; however, the underestimation is much
higher (>100 % always) for FM compared to RTPS covariance inflation
method.
BibTeX:
@article{WOS:000961064700001,
  author = {Bisht, Jagat S. H. and Patra, Prabir K. and Takigawa, Masayuki and
Sekiya, Takashi and Kanaya, Yugo and Saitoh, Naoko and Miyazaki,
Kazuyuki}, title = {Estimation of CH4 emission based on an advanced 4D-LETKF
assimilation system}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2023}, volume = {16}, number = {6}, pages = {1823-1838}, doi = {https://doi.org/10.5194/gmd-16-1823-2023} }
Liu, X. and Zhuang, Q. Methane emissions from Arctic landscapes during 2000-2015: an analysis
withland and lake biogeochemistry models
2023 BIOGEOSCIENCES
Vol. 20(6), pp. 1181-1193 
article DOI  
Abstract: Wetlands and freshwater bodies (mainly lakes) are the largest natural
sources of the greenhouse gas CH4 to the atmosphere. Great efforts have
been made to quantify these source emissions and their uncertainties.
Previous research suggests that there might be significant uncertainties
coming from ``double accounting'' emissions from freshwater bodies and
wetlands. Here we quantify the methane emissions from both land and
freshwater bodies in the pan-Arctic with two process-based
biogeochemistry models by minimizing the double accounting at the
landscape scale. Two non-overlapping dynamic areal change datasets are
used to drive the models. We estimate that the total methane emissions
from the pan-Arctic are 36.46 +/- 1.02 Tg CH4 yr(-1)during 2000-2015, of
which wetlands and freshwater bodies are 21.69 +/- 0.59 Tg CH4 yr(-1)
and 14.76 +/- 0.44 Tg CH4 yr(-1), respectively. Our estimation narrows
the difference between previous bottom-up (53.9 Tg CH4 yr(-1)) and
top-down (29 Tg CH4 yr(-1)) estimates. Our correlation analysis shows
that air temperature is the most important driver for methane emissions
of inland water systems. Wetland emissions are also significantly
affected by vapor pressure, while lake emissions are more influenced by
precipitation and landscape areal changes. Sensitivity tests indicate
that pan-Arctic lake CH4 emissions were highly influenced by air
temperature but less by lake sediment carbon increase.
BibTeX:
@article{WOS:000959121900001,
  author = {Liu, Xiangyu and Zhuang, Qianlai},
  title = {Methane emissions from Arctic landscapes during 2000-2015: an analysis
withland and lake biogeochemistry models}, journal = {BIOGEOSCIENCES}, year = {2023}, volume = {20}, number = {6}, pages = {1181-1193}, doi = {https://doi.org/10.5194/bg-20-1181-2023} }
Yu, X., Millet, D.B., Henze, D.K., Turner, A.J., Delgado, A.L., Bloom, A.A. and Sheng, J. A high-resolution satellite-based map of global methane emissions
reveals missing wetland, fossil fuel, and monsoon sources
2023 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 23(5), pp. 3325-3346 
article DOI  
Abstract: We interpret space-borne observations from the TROPOspheric Monitoring
Instrument (TROPOMI) in a multi-inversion framework to characterize the
2018-2019 global methane budget. Evaluation of the inverse solutions
indicates that simultaneous source + sink optimization using methane
observations alone remains an ill-posed problem - even with the dense
TROPOMI sampling coverage. Employing remote carbon monoxide (CO) and
hydroxyl radical (OH) observations with independent methane measurements
to distinguish between candidate solutions, we infer from TROPOMI a
global methane source of 587 (586-589) Tg yr(-1) and sink of 571 Tg
yr(-1) for our analysis period. We apply a new downscaling method to map
the derived monthly emissions to 0.1 degrees x 0.1 degrees resolution,
using the results to uncover key gaps in the prior methane budget. The
TROPOMI data point to an underestimate of tropical wetland emissions (a
posteriori increase of +13 % [6 %-25 %] or 20 [7-25] Tg yr(-1)),
with adjustments following regional hydrology. Some simple wetland
parameterizations represent these patterns as accurately as more
sophisticated process-based models. Emissions from fossil fuel
activities are strongly underestimated over the Middle East (+5 [2-6]
Tg yr(-1) a posteriori increase) and over Venezuela. The TROPOMI
observations also reveal many fossil fuel emission hotspots missing from
the prior inventory, including over Mexico, Oman, Yemen, Turkmenistan,
Iran, Iraq, Libya, and Algeria. Agricultural methane sources are
underestimated in India, Brazil, the California Central Valley, and
Asia. Overall, anthropogenic sources worldwide are increased by +19
[11-31] Tg yr(-1) over the prior estimate. More than 45 % of this
adjustment occurs over India and Southeast Asia during the summer
monsoon (+8.5 [3.1-10.7] Tg in July-October), likely due to
rainfall-enhanced emissions from rice, manure, and landfills/sewers,
which increase during this season along with the natural wetland source.
BibTeX:
@article{WOS:000953028200001,
  author = {Yu, Xueying and Millet, Dylan B. and Henze, Daven K. and Turner,
Alexander J. and Delgado, Alba Lorente and Bloom, A. Anthony and Sheng,
Jianxiong}, title = {A high-resolution satellite-based map of global methane emissions
reveals missing wetland, fossil fuel, and monsoon sources}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2023}, volume = {23}, number = {5}, pages = {3325-3346}, doi = {https://doi.org/10.5194/acp-23-3325-2023} }
Song, W., Yao, W., Zhao, Y., Wang, M., Chen, R., Zhu, Z., Gao, Z., Li, C., Liang, M. and Yu, D. City-Level CH4 Emissions from Anthropogenic Sources and Its
Environmental Behaviors in China's Cold Cities
2023 ATMOSPHERE
Vol. 14(3) 
article DOI  
Abstract: Distinguished features of cities influence the characteristics of CH4
emissions. A city-level emission inventory represents the
characteristics of CH4 on a smaller scale, according to the special
factors in each city. A city-level emission inventory was established to
reveal the characteristics and source profile of CH4 emissions in the
coldest province, which is a typical provincial cold region in northeast
China. The dominant sources were identified for targeted cities. Rice
cultivation, coal mining, oil and gas exploitation, and livestock are
the dominant emission sectors. Emissions from other sectors, including
wastewater disposal, biomass burning, landfill, etc. were also
estimated. The provincial CH4 emissions increased gradually from 2003 to
2012, up to 2993.26 Gg with an annual increase rate of 2.85%; the
emissions were 2740.63 in 2020. The emissions of CH4 in Harbin, Daqing,
Jiamusi, and Hegang cities were higher than in the other nine cities,
which were 337.23 Gg, 330.01 Gg, 328.55 Gg, and 307.42 Gg in 2020,
respectively. Agriculture, including the rice cultivation, livestock,
and biomass burning sectors contributed to 51.24-62.12% of total
emissions, and the contributions increased gradually. Coal mining, oil
and gas exploration, and fossil fuel combustion are energy-related
sources, which contributed up to 37.91% of the total emissions, and the
proportion kept decreasing to 23.87% in 2020. Furthermore,
meteorological factors are especially relevant to the region, by which
the differences of ambient temperature are over 60 degrees C (+/- 30
degrees C). In the summer, CH4 emissions from the rice cultivation,
biomass burning, livestock, and landfill sectors are obviously distinct
from the heating period (winter), while few differences in CH4 emissions
are found from wastewater disposal and the fossil fuel production
sectors.
BibTeX:
@article{WOS:000954626500001,
  author = {Song, Weiwei and Yao, Wanying and Zhao, Yixuan and Wang, Mengying and
Chen, Ruihan and Zhu, Zhiyu and Gao, Zhi and Li, Chunhui and Liang, Miao
and Yu, Dajiang}, title = {City-Level CH4 Emissions from Anthropogenic Sources and Its
Environmental Behaviors in China's Cold Cities}, journal = {ATMOSPHERE}, year = {2023}, volume = {14}, number = {3}, doi = {https://doi.org/10.3390/atmos14030535} }
Watts, J.D., Farina, M., Kimball, J.S., Schiferl, L.D., Liu, Z., Arndt, K.A., Zona, D., Ballantyne, A., Euskirchen, E.S., Parmentier, F.-J.W., Helbig, M., Sonnentag, O., Tagesson, T., Rinne, J., Ikawa, H., Ueyama, M., Kobayashi, H., Sachs, T., Nadeau, D.F., Kochendorfer, J., Jackowicz-Korczynski, M., Virkkala, A., Aurela, M., Commane, R., Byrne, B., Birch, L., Johnson, M.S., Madani, N., Rogers, B., Du, J., Endsley, A., Savage, K., Poulter, B., Zhang, Z., Bruhwiler, L.M., Miller, C.E., Goetz, S. and Oechel, W.C. Carbon uptake in Eurasian boreal forests dominates the high-latitude net
ecosystem carbon budget
2023 GLOBAL CHANGE BIOLOGY
Vol. 29(7), pp. 1870-1889 
article DOI  
Abstract: Arctic-boreal landscapes are experiencing profound warming, along with
changes in ecosystem moisture status and disturbance from fire. This
region is of global importance in terms of carbon feedbacks to climate,
yet the sign (sink or source) and magnitude of the Arctic-boreal carbon
budget within recent years remains highly uncertain. Here, we provide
new estimates of recent (2003-2015) vegetation gross primary
productivity (GPP), ecosystem respiration (R-eco), net ecosystem CO2
exchange (NEE; R-eco - GPP), and terrestrial methane (CH4) emissions for
the Arctic-boreal zone using a satellite data-driven process-model for
northern ecosystems (TCFM-Arctic), calibrated and evaluated using
measurements from >60 tower eddy covariance (EC) sites. We used
TCFM-Arctic to obtain daily 1-km(2) flux estimates and annual carbon
budgets for the pan-Arctic-boreal region. Across the domain, the model
indicated an overall average NEE sink of -850 Tg CO2-C year(-1).
Eurasian boreal zones, especially those in Siberia, contributed to a
majority of the net sink. In contrast, the tundra biome was relatively
carbon neutral (ranging from small sink to source). Regional CH4
emissions from tundra and boreal wetlands (not accounting for aquatic
CH4) were estimated at 35 Tg CH4-C year(-1). Accounting for additional
emissions from open water aquatic bodies and from fire, using available
estimates from the literature, reduced the total regional NEE sink by
21% and shifted many far northern tundra landscapes, and some boreal
forests, to a net carbon source. This assessment, based on in situ
observations and models, improves our understanding of the high-latitude
carbon status and also indicates a continued need for integrated
site-to-regional assessments to monitor the vulnerability of these
ecosystems to climate change.
BibTeX:
@article{WOS:000915387000001,
  author = {Watts, Jennifer D. and Farina, Mary and Kimball, John S. and Schiferl,
Luke D. and Liu, Zhihua and Arndt, Kyle A. and Zona, Donatella and
Ballantyne, Ashley and Euskirchen, Eugenie S. and Parmentier, Frans-Jan
W. and Helbig, Manuel and Sonnentag, Oliver and Tagesson, Torbern and
Rinne, Janne and Ikawa, Hiroki and Ueyama, Masahito and Kobayashi,
Hideki and Sachs, Torsten and Nadeau, Daniel F. and Kochendorfer, John
and Jackowicz-Korczynski, Marcin and Virkkala, Anna and Aurela, Mika and
Commane, Roisin and Byrne, Brendan and Birch, Leah and Johnson, Matthew
S. and Madani, Nima and Rogers, Brendan and Du, Jinyang and Endsley,
Arthur and Savage, Kathleen and Poulter, Ben and Zhang, Zhen and
Bruhwiler, Lori M. and Miller, Charles E. and Goetz, Scott and Oechel,
Walter C.}, title = {Carbon uptake in Eurasian boreal forests dominates the high-latitude net
ecosystem carbon budget}, journal = {GLOBAL CHANGE BIOLOGY}, year = {2023}, volume = {29}, number = {7}, pages = {1870-1889}, doi = {https://doi.org/10.1111/gcb.16553} }
Wang, H., Zhao, Z., Wu, Y. and Luo, X. B-Spline Method for Spatio-Temporal Inverse Model 2022 JOURNAL OF SYSTEMS SCIENCE &amp; COMPLEXITY
Vol. 35(6), pp. 2336-2360 
article DOI  
Abstract: Inverse models can be used to estimate surface fluxes in terms of the
observed atmospheric concentration measurement data. This paper proposes
a new nonparametric spatio-temporal inverse model and provides the
global expressions for the estimates by employing the B-spline method.
The authors establish the asymptotic normality of the estimators under
mild conditions. The authors also conduct numerical studies to evaluate
the finite sample performance of the proposed methodologies. Finally,
the authors apply the method to anthropogenic carbon dioxide (CO2)
emission data from different provinces of Canada to illustrate the
validity of the proposed techniques.
BibTeX:
@article{WOS:000905679100017,
  author = {Wang, Hongxia and Zhao, Zihan and Wu, Yuehua and Luo, Xuehong},
  title = {B-Spline Method for Spatio-Temporal Inverse Model},
  journal = {JOURNAL OF SYSTEMS SCIENCE &amp; COMPLEXITY},
  year = {2022},
  volume = {35},
  number = {6},
  pages = {2336-2360},
  doi = {https://doi.org/10.1007/s11424-022-1206-5}
}
Yang, T., He, Q., Jiang, J., Sheng, L., Jiang, H. and He, C. Impact of Water Table on Methane Emission Dynamics in Terrestrial
Wetlands and Implications on Strategies for Wetland Management and
Restoration
2022 WETLANDS
Vol. 42(8) 
article DOI  
Abstract: Methane is a potent greenhouse gas. Wetlands are considered as
significant sources of methane emission, prompting the need to
understand determinants of methane flux in these critical ecosystems.
The importance of the water table in methane emission has been noted in
terrestrial wetlands; however, the role of the water table in methane
emission remains to be clarified in order for the development of
strategies to mitigate methane emission from wetland ecosystems. This
review examines the current literature on factors influencing methane
emission in terrestrial wetlands. The water table was illustrated as an
overriding factor that controls both methane generation and consumption.
The contribution of other main factors, including substrate
characteristics, wetland plants and temperature, to methane emission was
also discussed. Building upon the growing understanding of processes
underlying methane emission, strategies centered around the control of
water table was proposed to minimize methane emission in wetland
management and restoration efforts to maximize the ecological value of
wetlands.
BibTeX:
@article{WOS:000893918900003,
  author = {Yang, Tao and He, Qiang and Jiang, Jing and Sheng, Lianxi and Jiang,
Haibo and He, Chunguang}, title = {Impact of Water Table on Methane Emission Dynamics in Terrestrial
Wetlands and Implications on Strategies for Wetland Management and
Restoration}, journal = {WETLANDS}, year = {2022}, volume = {42}, number = {8}, doi = {https://doi.org/10.1007/s13157-022-01634-7} }
Barton-Grimley, R.A., Nehrir, A.R., Kooi, S.A., Collins, J.E., Harper, D.B., Notari, A., Lee, J., DiGangi, J.P., Choi, Y. and Davis, K.J. Evaluation of the High Altitude Lidar Observatory (HALO) methane
retrievals during the summer 2019 ACT-America campaign
2022 ATMOSPHERIC MEASUREMENT TECHNIQUES
Vol. 15(15), pp. 4623-4650 
article DOI  
Abstract: The NASA Langley Research Center High Altitude Lidar Observatory (HALO)
is a multi-functional and modular lidar developed to address the
observational needs of NASA's weather, climate, carbon cycle, and
atmospheric composition focus areas. HALO measures atmospheric H2O
mixing ratios, CH4 mole fractions, and aerosol/cloud optical properties
using the differential absorption lidar (DIAL) and
high-spectral-resolution lidar (HSRL) techniques. In 2019 HALO
participated in the NASA Atmospheric Carbon and Transport - America
campaign on board the NASA C-130 to complement a suite of greenhouse gas
in situ sensors and provide, for the first time, simultaneous
measurements of column CH4 and aerosol/cloud profiles. HALO operated in
18 of 19 science flights where the DIAL and integrated path differential
absorption (IPDA) lidar techniques at 1645 nm were used for column and
multi-layer measurements of CH4 mole fractions, and the HSRL and
backscatter techniques were used at 532 and 1064 nm, respectively, for
retrievals of aerosol backscatter, extinction, depolarization, and
mixing layer heights. In this paper we present HALO's measurement theory
for the retrievals of column and multi-layer XCH4, retrieval accuracy,
and precision including methods for bias correction and a comprehensive
total column XCH4 validation comparison to in situ observations.
Comparisons of HALO XCH4 to in situ-derived XCH4, collected during
spiral ascents and descents, indicate a mean difference of 2.54 ppb and
standard deviation (SD) of the differences of 16.66 ppb when employing
15 s along-track averaging (< 3 km). A high correlation coefficient of R
= 0.9058 was observed for the 11 in situ spiral comparisons. Column XCH4
measured by HALO over regional scales covered by the ACT-America
campaign is compared against in situ CH4 measurements carried out within
the planetary boundary layer (PBL) from both the C-130 and B200
aircraft. Favorable correlation between the in situ point measurements
within the PBL and the remote column measurements from HALO elucidates
the sensitivity of a column-integrating lidar to CH4 variability within
the PBL, where surface fluxes dominate the signal. Novel capabilities
for CH4 profiling in regions of clear air using the DIAL technique are
presented and validated for the first time. Additionally, profiling of
CH4 is used to apportion the PBL absorption from the total column and is
compared to previously reported IPDA cloud slicing techniques that
estimate PBL columns using strong echoes from fair weather cumulus. The
analysis presented here points towards HALO's ability to retrieve
accurate and precise CH4 columns with the prospects for future
multilayer profiling in support of future suborbital campaigns.
BibTeX:
@article{WOS:000840451700001,
  author = {Barton-Grimley, Rory A. and Nehrir, Amin R. and Kooi, Susan A. and
Collins, James E. and Harper, David B. and Notari, Anthony and Lee,
Joseph and DiGangi, Joshua P. and Choi, Yonghoon and Davis, Kenneth J.}, title = {Evaluation of the High Altitude Lidar Observatory (HALO) methane
retrievals during the summer 2019 ACT-America campaign}, journal = {ATMOSPHERIC MEASUREMENT TECHNIQUES}, year = {2022}, volume = {15}, number = {15}, pages = {4623-4650}, doi = {https://doi.org/10.5194/amt-15-4623-2022} }
Salmon, E., Jegou, F., Guenet, B., Jourdain, L., Qiu, C., Bastrikov, V., Guimbaud, C., Zhu, D., Ciais, P., Peylin, P., Gogo, S., Laggoun-Defarge, F., Aurela, M., Bret-Harte, M.S., Chen, J., Chojnicki, B.H., Chu, H., Edgar, C.W., Euskirchen, E.S., Flanagan, L.B., Fortuniak, K., Holl, D., Klatt, J., Kolle, O., Kowalska, N., Kutzbach, L., Lohila, A., Merbold, L., Pawlak, W., Sachs, T. and Ziemblinska, K. Assessing methane emissions for northern peatlands in ORCHIDEE-PEAT
revision 7020
2022 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 15(7), pp. 2813-2838 
article DOI  
Abstract: In the global methane budget, the largest natural source is attributed
to wetlands, which encompass all ecosystems composed of waterlogged or
inundated ground, capable of methane production. Among them, northern
peatlands that store large amounts of soil organic carbon have been
functioning, since the end of the last glaciation period, as long-term
sources of methane (CH4) and are one of the most significant methane
sources among wetlands. To reduce uncertainty of quantifying methane
flux in the global methane budget, it is of significance to understand
the underlying processes for methane production and fluxes in northern
peatlands. A methane model that features methane production and
transport by plants, ebullition process and diffusion in soil, oxidation
to CO2, and CH4 fluxes to the atmosphere has been embedded in the
ORCHIDEE-PEAT land surface model that includes an explicit
representation of northern peatlands. ORCHIDEE-PCH4 was calibrated and
evaluated on 14 peatland sites distributed on both the Eurasian and
American continents in the northern boreal and temperate regions. Data
assimilation approaches were employed to optimized parameters at each
site and at all sites simultaneously. Results show that methanogenesis
is sensitive to temperature and substrate availability over the top 75
cm of soil depth. Methane emissions estimated using single site
optimization (SSO) of model parameters are underestimated by 9 g CH4
m(-2) yr(-1) on average (i.e., 50 % higher than the site average of
yearly methane emissions). While using the multi-site optimization
(MSO), methane emissions are overestimated by 5 g CH4 m(-2) yr(-1) on
average across all investigated sites (i.e., 37 % lower than the site
average of yearly methane emissions).
BibTeX:
@article{WOS:000792361900001,
  author = {Salmon, Elodie and Jegou, Fabrice and Guenet, Bertrand and Jourdain,
Line and Qiu, Chunjing and Bastrikov, Vladislav and Guimbaud, Christophe
and Zhu, Dan and Ciais, Philippe and Peylin, Philippe and Gogo,
Sebastien and Laggoun-Defarge, Fatima and Aurela, Mika and Bret-Harte,
M. Syndonia and Chen, Jiquan and Chojnicki, Bogdan H. and Chu, Housen
and Edgar, Colin W. and Euskirchen, Eugenie S. and Flanagan, Lawrence B.
and Fortuniak, Krzysztof and Holl, David and Klatt, Janina and Kolle,
Olaf and Kowalska, Natalia and Kutzbach, Lars and Lohila, Annalea and
Merbold, Lutz and Pawlak, Wlodzimierz and Sachs, Torsten and
Ziemblinska, Klaudia}, title = {Assessing methane emissions for northern peatlands in ORCHIDEE-PEAT
revision 7020}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2022}, volume = {15}, number = {7}, pages = {2813-2838}, doi = {https://doi.org/10.5194/gmd-15-2813-2022} }
Li, L., Lei, L., Song, H., Zeng, Z. and He, Z. Spatiotemporal Geostatistical Analysis and Global Mapping of
CH4 Columns from GOSAT Observations
2022 REMOTE SENSING
Vol. 14(3) 
article DOI  
Abstract: Methane (CH4) is one of the most important greenhouse gases causing the
global warming effect. The mapping data of atmospheric CH4
concentrations in space and time can help us better to understand the
characteristics and driving factors of CH4 variation as to support the
actions of CH4 emission reduction for preventing the continuous increase
of atmospheric CH4 concentrations. In this study, we applied a
spatiotemporal geostatistical analysis and prediction to develop an
approach to generate the mapping CH4 dataset (Mapping-XCH4) in 1 degrees
grid and three days globally using column averaged dry air mole fraction
of CH4 (XCH4) data derived from observations of the Greenhouse Gases
Observing Satellite (GOSAT) from April 2009 to April 2020.
Cross-validation for the spatiotemporal geostatistical predictions
showed better correlation coefficient of 0.97 and a mean absolute
prediction error of 7.66 ppb. The standard deviation is 11.42 ppb when
comparing the Mapping-XCH4 data with the ground measurements from the
total carbon column observing network (TCCON). Moreover, we assessed the
performance of this Mapping-XCH4 dataset by comparing with the XCH4
simulations from the CarbonTracker model and primarily investigating the
variations of XCH4 from April 2009 to April 2020. The results showed
that the mean annual increase in XCH4 was 7.5 ppb/yr derived from
Mapping-XCH4, which was slightly greater than 7.3 ppb/yr from the ground
observational network during the past 10 years from 2010. XCH4 is larger
in South Asia and eastern China than in the other regions, which agrees
with the XCH4 simulations. The Mapping-XCH4 shows a significant linear
relationship and a correlation coefficient of determination (R-2) of
0.66, with EDGAR emission inventories over Monsoon Asia. Moreover, we
found that Mapping-XCH4 could detect the reduction of XCH4 in the period
of lockdown from January to April 2020 in China, likely due to the
COVID-19 pandemic. In conclusion, we can apply GOSAT observations over a
long period from 2009 to 2020 to generate a spatiotemporally continuous
dataset globally using geostatistical analysis. This long-term
Mpping-XCH4 dataset has great potential for understanding the
spatiotemporal variations of CH4 concentrations induced by natural
processes and anthropogenic emissions at a global and regional scale.
BibTeX:
@article{WOS:000759879400001,
  author = {Li, Luman and Lei, Liping and Song, Hao and Zeng, Zhaocheng and He,
Zhonghua}, title = {Spatiotemporal Geostatistical Analysis and Global Mapping of
CH4 Columns from GOSAT Observations}, journal = {REMOTE SENSING}, year = {2022}, volume = {14}, number = {3}, doi = {https://doi.org/10.3390/rs14030654} }
Tenkanen, M., Tsuruta, A., Rautiainen, K., Kangasaho, V., Ellul, R. and Aalto, T. Utilizing Earth Observations of Soil Freeze/Thaw Data and Atmospheric
Concentrations to Estimate Cold Season Methane Emissions in the Northern
High Latitudes
2021 REMOTE SENSING
Vol. 13(24) 
article DOI  
Abstract: The northern wetland methane emission estimates have large
uncertainties. Inversion models are a qualified method to estimate the
methane fluxes and emissions in northern latitudes but when atmospheric
observations are sparse, the models are only as good as their a priori
estimates. Thus, improving a priori estimates is a competent way to
reduce uncertainties and enhance emission estimates in the sparsely
sampled regions. Here, we use a novel way to integrate remote sensing
soil freeze/thaw (F/T) status from SMOS satellite to better capture the
seasonality of methane emissions in the northern high latitude. The SMOS
F/T data provide daily information of soil freezing state in the
northern latitudes, and in this study, the data is used to define the
cold season in the high latitudes and, thus, improve our knowledge of
the seasonal cycle of biospheric methane fluxes. The SMOS F/T data is
implemented to LPX-Bern DYPTOP model estimates and the modified fluxes
are used as a biospheric a priori in the inversion model CarbonTracker
Europe-CH4. The implementation of the SMOS F/T soil state is shown to be
beneficial in improving the inversion model's cold season biospheric
flux estimates. Our results show that cold season biospheric CH4
emissions in northern high latitudes are approximately 0.60 Tg lower
than previously estimated, which corresponds to 17% reduction in the
cold season biospheric emissions. This reduction is partly compensated
by increased anthropogenic emissions in the same area (0.23 Tg), and the
results also indicates that the anthropogenic emissions could have even
larger contribution in cold season than estimated here.
BibTeX:
@article{WOS:000771728900014,
  author = {Tenkanen, Maria and Tsuruta, Aki and Rautiainen, Kimmo and Kangasaho,
Vilma and Ellul, Raymond and Aalto, Tuula}, title = {Utilizing Earth Observations of Soil Freeze/Thaw Data and Atmospheric
Concentrations to Estimate Cold Season Methane Emissions in the Northern
High Latitudes}, journal = {REMOTE SENSING}, year = {2021}, volume = {13}, number = {24}, doi = {https://doi.org/10.3390/rs13245059} }
Li, L. and Xue, B. Methane emissions from northern lakes under climate change: a review 2021 SN APPLIED SCIENCES
Vol. 3(12) 
article DOI  
Abstract: Northern lakes are important sources of CH4 in the atmosphere under the
background of permafrost thaw and winter warming. We synthesize studies
on thermokarst lakes, including various carbon sources for CH4 emission
and the influence of thermokarst drainage on carbon emission, to show
the evasion potential of ancient carbon that stored in the permafrost
and CH4 emission dynamics along with thermokarst lake evolution.
Besides, we discuss the lake CH4 dynamics in seasonally ice-covered
lakes, especially for under-ice CH4 accumulation and emission during
spring ice melt and the possible influential factors for CH4 emission in
ice-melt period. We summarize the latest findings and point out that
further research should be conducted to investigate the possibility of
abundant ancient carbon emission from thermokarst lakes under climate
warming and quantify the contribution of ice-melt CH4 emission from
northern lakes on a large scale.
BibTeX:
@article{WOS:000722225200003,
  author = {Li, Lingling and Xue, Bin},
  title = {Methane emissions from northern lakes under climate change: a review},
  journal = {SN APPLIED SCIENCES},
  year = {2021},
  volume = {3},
  number = {12},
  doi = {https://doi.org/10.1007/s42452-021-04869-x}
}
Kuhn, M.A., Varner, R.K., Bastviken, D., Crill, P., MacIntyre, S., Turetsky, M., Walter Anthony, K., McGuire, A.D. and Olefeldt, D. BAWLD-CH4: a comprehensive dataset of methane fluxes from
boreal and arctic ecosystems
2021 EARTH SYSTEM SCIENCE DATA
Vol. 13(11), pp. 5151-5189 
article DOI  
Abstract: Methane (CH4) emissions from the boreal and arctic region are globally
significant and highly sensitive to climate change. There is currently a
wide range in estimates of high-latitude annual CH4 fluxes, where
estimates based on land cover inventories and empirical CH4 flux data or
process models (bottom-up approaches) generally are greater than
atmospheric inversions (top-down approaches). A limitation of bottom-up
approaches has been the lack of harmonization between inventories of
site-level CH4 flux data and the land cover classes present in
high-latitude spatial datasets. Here we present a comprehensive dataset
of small-scale, surface CH4 flux data from 540 terrestrial sites
(wetland and non-wetland) and 1247 aquatic sites (lakes and ponds),
compiled from 189 studies. The Boreal-Arctic Wetland and Lake Methane
Dataset (BAWLD-CH4) was constructed in parallel with a compatible land
cover dataset, sharing the same land cover classes to enable refined
bottom-up assessments. BAWLD-CH4 includes information on site-level CH4
fluxes but also on study design (measurement method, timing, and
frequency) and site characteristics (vegetation, climate, hydrology,
soil, and sediment types, permafrost conditions, lake size and depth,
and our determination of land cover class). The different land cover
classes had distinct CH4 fluxes, resulting from definitions that were
either based on or co-varied with key environmental controls. Fluxes of
CH4 from terrestrial ecosystems were primarily influenced by water table
position, soil temperature, and vegetation composition, while CH4 fluxes
from aquatic ecosystems were primarily influenced by water temperature,
lake size, and lake genesis. Models could explain more of the
between-site variability in CH4 fluxes for terrestrial than aquatic
ecosystems, likely due to both less precise assessments of lake CH4
fluxes and fewer consistently reported lake site characteristics.
Analysis of BAWLD-CH4 identified both land cover classes and regions
within the boreal and arctic domain, where future studies should be
focused, alongside methodological approaches. Overall, BAWLD-CH4
provides a comprehensive dataset of CH4 emissions from high-latitude
ecosystems that are useful for identifying research opportunities, for
comparison against new field data, and model parameterization or
validation.
BibTeX:
@article{WOS:000715853800001,
  author = {Kuhn, McKenzie A. and Varner, Ruth K. and Bastviken, David and Crill,
Patrick and MacIntyre, Sally and Turetsky, Merritt and Walter Anthony,
Katey and McGuire, Anthony D. and Olefeldt, David}, title = {BAWLD-CH4: a comprehensive dataset of methane fluxes from
boreal and arctic ecosystems}, journal = {EARTH SYSTEM SCIENCE DATA}, year = {2021}, volume = {13}, number = {11}, pages = {5151-5189}, doi = {https://doi.org/10.5194/essd-13-5151-2021} }
Khade, V., Polavarapu, S.M., Neish, M., Houtekamer, P.L., Jones, D.B.A., Baek, S.-J., He, T.-L. and Gravel, S. The Environment and Climate Change Canada Carbon Assimilation System
(EC-CAS v1.0): demonstration with simulated CO observations
2021 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 14(5), pp. 2525-2544 
article DOI  
Abstract: In this study, we present the development of a new coupled weather and
carbon monoxide (CO) data assimilation system based on the Environment
and Climate Change Canada (ECCC) operational ensemble Kalman filter
(EnKF). The estimated meteorological state is augmented to include CO.
Variable localization is used to prevent the direct update of
meteorology by the observations of the constituents and vice versa.
Physical localization is used to damp spurious analysis increments far
from a given observation. Perturbed surface flux fields are used to
account for the uncertainty in CO due to errors in the surface fluxes.
The system is demonstrated for the estimation of three-dimensional CO
states using simulated observations from a variety of networks. First, a
hypothetically dense, uniformly distributed observation network is used
to demonstrate that the system is working. More realistic observation
networks, based on surface hourly observations, and space-based
observations provide a demonstration of the complementarity of the
different networks and further confirm the reasonable behavior of the
coupled assimilation system. Having demonstrated the ability to estimate
CO distributions, this system will be extended to estimate surface
fluxes in the future.
BibTeX:
@article{WOS:000648544300002,
  author = {Khade, Vikram and Polavarapu, Saroja M. and Neish, Michael and
Houtekamer, Pieter L. and Jones, Dylan B. A. and Baek, Seung-Jong and
He, Tai-Long and Gravel, Sylvie}, title = {The Environment and Climate Change Canada Carbon Assimilation System
(EC-CAS v1.0): demonstration with simulated CO observations}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2021}, volume = {14}, number = {5}, pages = {2525-2544}, doi = {https://doi.org/10.5194/gmd-14-2525-2021} }
Chandra, N., Patra, P.K., Bisht, J.S.H., Ito, A., Umezawa, T., Saigusa, N., Morimoto, S., Aoki, S., Janssens-Maenhout, G., Fujita, R., Takigawa, M., Watanabe, S., Saitoh, N. and Canadell, J.G. Emissions from the Oil and Gas Sectors, Coal Mining and Ruminant Farming
Drive Methane Growth over the Past Three Decades
2021 JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN
Vol. 99(2), pp. 309-337 
article DOI  
Abstract: Methane (CH4) is an important greenhouse gas and plays a significant
role in tropospheric and stratospheric chemistry. Despite the relevance
of methane (CH4) in human-induced climate change and air pollution
chemistry, there is no scientific consensus on the causes of changes in
its growth rates and variability over the past three decades. We use a
well-validated chemistry-transport model for simulating CH4
concentration and estimation of regional CH4 emissions by inverse
modeling during 1988-2016. The control simulations are conducted using
seasonally varying hydroxyl (OH) concentrations and assumed no
interannual variability. Using inverse modeling of atmospheric
observations, emission inventories, a wetland model, and a delta
C-13-CH4 box model, we show that reductions in emissions from Europe and
Russia since 1988, particularly from oil-gas exploitation and enteric
fermentation, led to decreased CH4 growth rates in the 1990s. This
period was followed by a quasi-stationary state of CH4 in the atmosphere
during the early 2000s. CH4 resumed growth from 2007, which we attribute
to increases in emissions from coal mining mainly in China and the
intensification of ruminant farming in tropical regions. A sensitivity
simulation using interannually varying OH shows that regional emission
estimates by inversion are unaffected for the mid- and high latitude
areas. We show that meridional shift in CH4 emissions toward the lower
latitudes and the increase in CH4 loss by hydroxyl (OH) over the tropics
finely balance out, keeping the CH4 gradients between the southern
hemispheric tropical and polar sites relatively unchanged during
1988-2016. The latitudinal emissions shift is confirmed using the global
distributions of the total column CH4 observations via satellite remote
sensing. During our analysis period, there is no evidence of emission
enhancement due to climate warming, including the boreal regions. These
findings highlight key sectors for effective emission reduction
strategies toward climate change mitigation.
BibTeX:
@article{WOS:000661005900005,
  author = {Chandra, Naveen and Patra, Prabir K. and Bisht, Jagat S. H. and Ito,
Akihiko and Umezawa, Taku and Saigusa, Nobuko and Morimoto, Shinji and
Aoki, Shuji and Janssens-Maenhout, Greet and Fujita, Ryo and Takigawa,
Masayuki and Watanabe, Shingo and Saitoh, Naoko and Canadell, Josep G.}, title = {Emissions from the Oil and Gas Sectors, Coal Mining and Ruminant Farming
Drive Methane Growth over the Past Three Decades}, journal = {JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN}, year = {2021}, volume = {99}, number = {2}, pages = {309-337}, doi = {https://doi.org/10.2151/jmsj.2021-015} }
Lu, X., Jacob, D.J., Zhang, Y., Maasakkers, J.D., Sulprizio, M.P., Shen, L., Qu, Z., Scarpelli, T.R., Nesser, H., Yantosca, R.M., Sheng, J., Andrews, A., Parker, R.J., Boesch, H., Bloom, A.A. and Ma, S. Global methane budget and trend, 2010-2017: complementarity of inverse
analyses using in situ (GLOBALVIEWplus CH4 ObsPack) and
satellite (GOSAT) observations
2021 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 21(6), pp. 4637-4657 
article DOI  
Abstract: We use satellite (GOSAT) and in situ (GLOBALVIEWplus CH4 ObsPack)
observations of atmospheric methane in a joint global inversion of
methane sources, sinks, and trends for the 2010-2017 period. The
inversion is done by analytical solution to the Bayesian optimization
problem, yielding closed-form estimates of information content to assess
the consistency and complementarity (or redundancy) of the satellite and
in situ data sets. We find that GOSAT and in situ observations are to a
large extent complementary, with GOSAT providing a stronger overall
constraint on the global methane distributions, but in situ observations
being more important for northern midlatitudes and for relaxing global
error correlations between methane emissions and the main methane sink
(oxidation by OH radicals). The in-situ-only and the GOSAT-only
inversions alone achieve 113 and 212 respective independent pieces of
information (DOFS) for quantifying mean 2010-2017 anthropogenic
emissions on 1009 global model grid elements, and respective DOFS of 67
and 122 for 2010-2017 emission trends. The joint GOSAT + in situ
inversion achieves DOFS of 262 and 161 for mean emissions and trends,
respectively. Thus, the in situ data increase the global information
content from the GOSAT-only inversion by 20 %-30 %. The in-situ-only
and GOSAT-only inversions show consistent corrections to regional
methane emissions but are less consistent in optimizing the global
methane budget. The joint inversion finds that oil and gas emissions in
the US and Canada are underestimated relative to the values reported by
these countries to the United Nations Framework Convention on Climate
Change (UNFCCC) and used here as prior estimates, whereas coal emissions
in China are overestimated. Wetland emissions in North America are much
lower than in the mean WetCHARTs inventory used as a prior estimate. Oil
and gas emissions in the US increase over the 2010-2017 period but
decrease in Canada and Europe. The joint inversion yields a global
methane emission of 551 Tg a(-1) averaged over 2010-2017 and a methane
lifetime of 11.2 years against oxidation by tropospheric OH (86% of the
methane sink).
BibTeX:
@article{WOS:000634733700003,
  author = {Lu, Xiao and Jacob, Daniel J. and Zhang, Yuzhong and Maasakkers, Joannes
D. and Sulprizio, Melissa P. and Shen, Lu and Qu, Zhen and Scarpelli,
Tia R. and Nesser, Hannah and Yantosca, Robert M. and Sheng, Jianxiong
and Andrews, Arlyn and Parker, Robert J. and Boesch, Hartmut and Bloom,
A. Anthony and Ma, Shuang}, title = {Global methane budget and trend, 2010-2017: complementarity of inverse
analyses using in situ (GLOBALVIEWplus CH4 ObsPack) and
satellite (GOSAT) observations}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2021}, volume = {21}, number = {6}, pages = {4637-4657}, doi = {https://doi.org/10.5194/acp-21-4637-2021} }
Lin, X., Zhang, W., Crippa, M., Peng, S., Han, P., Zeng, N., Yu, L. and Wang, G. A comparative study of anthropogenic CH4 emissions over China
based on the ensembles of bottom-up inventories
2021 EARTH SYSTEM SCIENCE DATA
Vol. 13(3), pp. 1073-1088 
article DOI  
Abstract: Atmospheric methane (CH4) is a potent greenhouse gas that is strongly
influenced by several human activities. China, as one of the major
agricultural and energy production countries, contributes considerably
to the global anthropogenic CH4 emissions by rice cultivation, ruminant
feeding, and coal production. Understanding the characteristics of
China's CH4 emissions is necessary for interpreting source contributions
and for further climate change mitigation. However, the scarcity of data
from some sources or years and spatially explicit information pose great
challenges to completing an analysis of CH4 emissions. This study
provides a comprehensive comparison of China's anthropogenic CH4
emissions by synthesizing the most current and publicly available
datasets (13 inventories). The results show that anthropogenic CH4
emissions differ widely among inventories, with values ranging from
44.4-57.5 TgCH(4) yr(-1) in 2010. The discrepancy primarily resulted
from the energy sector (27.3 %-60.0% of total emissions), followed by
the agricultural (26.9 %-50.8 %) and waste treatment (8.1 %-21.2 %)
sectors. Temporally, emissions among inventories stabilized in the 1990s
but increased significantly thereafter, with annual average growth rates
(AAGRs) of 2.6 %-4.0% during 2000-2010 but slower AAGRs of 0.5
%-2.2% during 2011-2015, and the emissions became relatively stable,
with AAGRs of 0.3 %-0.8 %, during 2015-2019 because of the stable
emissions from the energy sector (mainly coal production). Spatially,
there are large differences in emissions hotspot identification among
inventories, and incomplete information on emission patterns may mislead
or bias mitigation efforts for CH4 emission reductions. The availability
of detailed activity data for sectors or subsectors and the use of
region-specific emission factors play important roles in understanding
source contributions and reducing the uncertainty in bottom-up
inventories. Data used in this article are available at
https://doi.org/10.6084/m9.figshare.12720989 (Lin et al., 2021).
BibTeX:
@article{WOS:000630176700003,
  author = {Lin, Xiaohui and Zhang, Wen and Crippa, Monica and Peng, Shushi and Han,
Pengfei and Zeng, Ning and Yu, Lijun and Wang, Guocheng}, title = {A comparative study of anthropogenic CH4 emissions over China
based on the ensembles of bottom-up inventories}, journal = {EARTH SYSTEM SCIENCE DATA}, year = {2021}, volume = {13}, number = {3}, pages = {1073-1088}, doi = {https://doi.org/10.5194/essd-13-1073-2021} }
Zeng, Z.-C., Byrne, B., Gong, F.-Y., He, Z. and Lei, L. Correlation between paddy rice growth and satellite-observed methane
column abundance does not imply causation
2021 NATURE COMMUNICATIONS
Vol. 12(1) 
article DOI  
BibTeX:
@article{WOS:000621489800005,
  author = {Zeng, Zhao-Cheng and Byrne, Brendan and Gong, Fang-Ying and He, Zhonghua
and Lei, Liping}, title = {Correlation between paddy rice growth and satellite-observed methane
column abundance does not imply causation}, journal = {NATURE COMMUNICATIONS}, year = {2021}, volume = {12}, number = {1}, doi = {https://doi.org/10.1038/s41467-021-21434-7} }
Rasanen, A., Manninen, T., Korkiakoski, M., Lohila, A. and Virtanen, T. Predicting catchment-scale methane fluxes with multi-source remote
sensing
2021 LANDSCAPE ECOLOGY
Vol. 36(4), pp. 1177-1195 
article DOI  
Abstract: Context Spatial patterns of CH4 fluxes can be modeled with remotely
sensed data representing land cover, soil moisture and topography.
Spatially extensive CH4 flux measurements conducted with portable
analyzers have not been previously upscaled with remote sensing.
Objectives How well can the CH4 fluxes be predicted with plot-based
vegetation measures and remote sensing? How does the predictive skill of
the model change when using different combinations of predictor
variables? Methods We measured CH4 fluxes in 279 plots in a 12.4 km(2)
peatland-forest-mosaic landscape in Pallas area, northern Finland in
July 2019. We compared 20 different CH4 flux maps produced with
vegetation field data and remote sensing data including Sentinel-1,
Sentinel-2 and digital terrain model (DTM). Results The landscape acted
as a net source of CH4 (253-502 mu g m(-2) h(-1)) and the proportion of
source areas varied considerably between maps (12-50%). The amount of
explained variance was high in CH4 regressions (59-76%, nRMSE 8-10%).
Regressions including remote sensing predictors had better performance
than regressions with plot-based vegetation predictors. The most
important remote sensing predictors included VH-polarized Sentinel-1
features together with topographic wetness index and other DTM features.
Spatial patterns were most accurately predicted when the landscape was
divided into sinks and sources with remote sensing-based
classifications, and the fluxes were modeled for sinks and sources
separately. Conclusions CH4 fluxes can be predicted accurately with
multi-source remote sensing in northern boreal peatland landscapes. High
spatial resolution remote sensing-based maps constrain uncertainties
related to CH4 fluxes and their spatial patterns.
BibTeX:
@article{WOS:000616999000001,
  author = {Rasanen, Aleksi and Manninen, Terhikki and Korkiakoski, Mika and Lohila,
Annalea and Virtanen, Tarmo}, title = {Predicting catchment-scale methane fluxes with multi-source remote
sensing}, journal = {LANDSCAPE ECOLOGY}, year = {2021}, volume = {36}, number = {4}, pages = {1177-1195}, doi = {https://doi.org/10.1007/s10980-021-01194-x} }
Bruhwiler, L., Parmentier, F.-J.W., Crill, P., Leonard, M. and Palmer I, P. The Arctic Carbon Cycle and Its Response to Changing Climate 2021 CURRENT CLIMATE CHANGE REPORTS
Vol. 7(1), pp. 14-34 
article DOI  
Abstract: Purpose of Review The Arctic has experienced the most rapid change in
climate of anywhere on Earth, and these changes are certain to drive
changes in the carbon budget of the Arctic as vegetation changes, soils
warm, fires become more frequent, and wetlands evolve as permafrost
thaws. In this study, we review the extensive evidence for Arctic
climate change and effects on the carbon cycle. In addition, we
re-evaluate some of the observational evidence for changing Arctic
carbon budgets. Recent Findings Observations suggest a more active CO2
cycle in high northern latitude ecosystems. Evidence points to increased
uptake by boreal forests and Arctic ecosystems, as well as increasing
respiration, especially in autumn. However, there is currently no strong
evidence of increased CH4 emissions. Long-term observations using both
bottom-up (e.g., flux) and top-down (atmospheric abundance) approaches
are essential for understanding changing carbon cycle budgets.
Consideration of atmospheric transport is critical for interpretation of
top-down observations of atmospheric carbon.
BibTeX:
@article{WOS:000613966900001,
  author = {Bruhwiler, Lori and Parmentier, Frans-Jan W. and Crill, Patrick and
Leonard, Mark and Palmer, I, Paul}, title = {The Arctic Carbon Cycle and Its Response to Changing Climate}, journal = {CURRENT CLIMATE CHANGE REPORTS}, year = {2021}, volume = {7}, number = {1}, pages = {14-34}, doi = {https://doi.org/10.1007/s40641-020-00169-5} }
Yu, X., Millet, D.B., Wells, K.C., Henze, D.K., Cao, H., Griffis, T.J., Kort, E.A., Plant, G., Deventer, M.J., Kolka, R.K., Roman, D.T., Davis, K.J., Desai, A.R., Baier, B.C., McKain, K., Czarnetzki, A.C. and Bloom, A.A. Aircraft-based inversions quantify the importance of wetlands and
livestock for Upper Midwest methane emissions
2021 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 21(2), pp. 951-971 
article DOI  
Abstract: We apply airborne measurements across three seasons (summer, winter and
spring 2017-2018) in a multi-inversion framework to quantify methane
emissions from the US Corn Belt and Upper Midwest, a key agricultural
and wetland source region. Combing our seasonal results with prior fall
values we find that wetlands are the largest regional methane source (32
%, 20 [16-23] Gg/d), while livestock (enteric/manure; 25 %, 15
[14-17] Gg/d) are the largest anthropogenic source. Natural
gas/petroleum, waste/landfills, and coal mines collectively make up the
remainder. Optimized fluxes improve model agreement with independent
datasets within and beyond the study timeframe. Inversions reveal
coherent and seasonally dependent spatial errors in the WetCHARTs
ensemble mean wetland emissions, with an underestimate for the Prairie
Pothole region but an overestimate for Great Lakes coastal wetlands.
Wetland extent and emission temperature dependence have the largest
influence on prediction accuracy; better representation of cou- pled
soil temperature-hydrology effects is therefore needed. Our optimized
regional livestock emissions agree well with the Gridded EPA estimates
during spring (to within 7 %) but are similar to 25 % higher during
summer and winter. Spatial analysis further shows good top-down and
bottom-up agreement for beef facilities (with mainly enteric emissions)
but larger (similar to 30 %) seasonal discrepancies for dairies and hog
farms (with > 40 % manure emissions). Findings thus support bottom-up
enteric emission estimates but suggest errors for manure; we propose
that the latter reflects inadequate treatment of management factors
including field application. Overall, our results confirm the importance
of intensive animal agriculture for regional methane emissions, implying
substantial mitigation opportunities through improved management.
BibTeX:
@article{WOS:000613269200002,
  author = {Yu, Xueying and Millet, Dylan B. and Wells, Kelley C. and Henze, Daven
K. and Cao, Hansen and Griffis, Timothy J. and Kort, Eric A. and Plant,
Genevieve and Deventer, Malte J. and Kolka, Randall K. and Roman, D.
Tyler and Davis, Kenneth J. and Desai, Ankur R. and Baier, Bianca C. and
McKain, Kathryn and Czarnetzki, Alan C. and Bloom, A. Anthony}, title = {Aircraft-based inversions quantify the importance of wetlands and
livestock for Upper Midwest methane emissions}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2021}, volume = {21}, number = {2}, pages = {951-971}, doi = {https://doi.org/10.5194/acp-21-951-2021} }
Stanevich, I., Jones, D.B.A., Strong, K., Parker, R.J., Boesch, H., Wunch, D., Notholt, J., Petri, C., Warneke, T., Sussmann, R., Schneider, M., Hase, F., Kivi, R., Deutscher, N.M., Velazco, V.A., Walker, K.A. and Deng, F. Characterizing model errors in chemical transport modeling of methane:
impact of model resolution in versions v9-02 of GEOS-Chem and v35j of
its adjoint model
2020 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 13(9), pp. 3839-3862 
article DOI  
Abstract: The GEOS-Chem simulation of atmospheric CH4 was evaluated against
observations from the Thermal and Near Infrared Sensor for Carbon
Observations Fourier Transform Spectrometer (TANSO-FTS) on the
Greenhouse Gases Observing Satellite (GOSAT), the Atmospheric Chemistry
Experiment Fourier Transform Spectrometer (ACE-FTS), and the Total
Carbon Column Observing Network (TCCON). We focused on the model
simulations at the 4 degrees x 5 degrees and 2 degrees x 2.5 degrees
horizontal resolutions for the period of February-May 2010. Compared to
the GOSAT, TCCON, and ACE-FTS data, we found that the 2 degrees x 2.5
degrees model produced a better simulation of CH4, with smaller biases
and a higher correlation to the independent data. We found large
resolution-dependent differences such as a latitude-dependent XCH4 bias,
with higher column abundances of CH4 at high latitudes and lower
abundances at low latitudes at the 4 degrees x 5 degrees resolution than
at 2 degrees x 2.5 degrees. We also found large differences in CH4
column abundances between the two resolutions over major source regions
such as China. These differences resulted in up to 30 % differences in
inferred regional CH4 emission estimates from the two model resolutions.
We performed several experiments using Rn-222, Be-7, and CH4 to
determine the origins of the resolution-dependent errors. The results
suggested that the major source of the latitude-dependent errors is
excessive mixing in the upper troposphere and lower stratosphere,
including mixing at the edge of the polar vortex, which is pronounced at
the 4 degrees x 5 degrees resolution. At the coarser resolution, there
is weakened vertical transport in the troposphere at midlatitudes to
high latitudes due to the loss of sub-grid tracer eddy mass flux in the
storm track regions. The vertical air mass fluxes are calculated in the
model from the degraded coarse-resolution wind fields and the model does
not conserve the air mass flux between model resolutions; as a result,
the low resolution does not fully capture the vertical transport. This
produces significant localized discrepancies, such as much greater CH4
abundances in the lower troposphere over China at 4 degrees x 5 degrees
than at 2 degrees x 2.5 degrees. Although we found that the CH4
simulation is significantly better at 2 degrees x 2.5 degrees than at 4
degrees x 5 degrees, biases may still be present at 2 degrees x 2.5
degrees resolution. Their importance, particularly in regards to inverse
modeling of CH4 emissions, should be evaluated in future studies using
online transport in the native general circulation model as a benchmark
simulation.
BibTeX:
@article{WOS:000566779800002,
  author = {Stanevich, Ilya and Jones, Dylan B. A. and Strong, Kimberly and Parker,
Robert J. and Boesch, Hartmut and Wunch, Debra and Notholt, Justus and
Petri, Christof and Warneke, Thorsten and Sussmann, Ralf and Schneider,
Matthias and Hase, Frank and Kivi, Rigel and Deutscher, Nicholas M. and
Velazco, Voltaire A. and Walker, Kaley A. and Deng, Feng}, title = {Characterizing model errors in chemical transport modeling of methane:
impact of model resolution in versions v9-02 of GEOS-Chem and v35j of
its adjoint model}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2020}, volume = {13}, number = {9}, pages = {3839-3862}, doi = {https://doi.org/10.5194/gmd-13-3839-2020} }
Li, T., Lu, Y., Yu, L., Sun, W., Zhang, Q., Zhang, W., Wang, G., Qin, Z., Yu, L., Li, H. and Zhang, R. Evaluation of CH4MODwetland and Terrestrial Ecosystem Model
(TEM) used to estimate global CH4 emissions from natural
wetlands
2020 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 13(8), pp. 3769-3788 
article DOI  
Abstract: Wetlands are the largest and most uncertain natural sources of
atmospheric methane (CH4). Several process-based models have been
developed to quantify the magnitude and estimate spatial and temporal
variations in CH4 emissions from global wetlands. Reliable models are
required to estimate global wetland CH4 emissions. This study aimed to
test two process-based models, CH4 MODwetland and Terrestrial Ecosystem
Model (TEM), against the CH4 flux measurements of marsh, swamp, peatland
and coastal wetland sites across the world; specifically, model accuracy
and generality were evaluated for different wetland types and in
different continents, and then the global CH4 emissions from 2000 to
2010 were estimated. Both models showed similar high correlations with
the observed seasonal/annual total CH4 emissions, and the regression of
the observed versus computed total seasonal/annual CH4 emissions
resulted in R-2 values of 0.81 and 0.68 for CH4 MODwetland and ILM,
respectively. The CH4MOD(wetland )produced accurate predictions for
marshes, peatlands, swamps and coastal wetlands, with model efficiency
(EF) values of 0.22, 0.52, 0.13 and 0.72, respectively. TEM produced
good predictions for peatlands and swamps, with EF values of 0.69 and
0.74, respectively, but it could not accurately simulate marshes and
coastal wetlands (EF < 0). There was a good correlation between the
simulated CH4 fluxes and the observed values on most continents.
However, CH4MOD(wetland) showed no correlation with the observed values
in South America and Africa. TEM showed no correlation with the
observations in Europe. The global CH4 emissions for the period
2000-2010 were estimated to be 105.31 +/- 2.72 Tg yr(-1) by CH4
MODwetland and 134.31 +/- 0.84 Tg yr(-1) by MM. Both models simulated a
similar spatial distribution of CH4 emissions globally and on different
continents. Marshes contribute 36 %-39 % of global CH4 emissions.
Lakes/rivers and swamps are the second and third greatest contributors,
respectively. Other wetland types account for only approximately 20 %
of global emissions. Based on the model applicability, if we use the
more accurate model, i.e., the one that performs best as evidenced by a
higher model efficiency and a lower model bias, to estimate each
continent and wetland type, we obtain a new assessment of 116.99-124.74
Tg yr(-1) for the global CH4 emissions for the period 2000-2010. Our
results imply that performance at a global scale may conceal model
uncertainty. Efforts should be made to improve model accuracy for
different wetland types and regions, particularly hotspot regions, to
reduce the uncertainty in global assessments.
BibTeX:
@article{WOS:000566347300001,
  author = {Li, Tingting and Lu, Yanyu and Yu, Lingfei and Sun, Wenjuan and Zhang,
Qing and Zhang, Wen and Wang, Guocheng and Qin, Zhangcai and Yu, Lijun
and Li, Hailing and Zhang, Ran}, title = {Evaluation of CH4MODwetland and Terrestrial Ecosystem Model
(TEM) used to estimate global CH4 emissions from natural
wetlands}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2020}, volume = {13}, number = {8}, pages = {3769-3788}, doi = {https://doi.org/10.5194/gmd-13-3769-2020} }
Matthews, E., Johnson, M.S., Genovese, V., Du, J. and Bastviken, D. Methane emission from high latitude lakes: methane-centric lake
classification and satellite-driven annual cycle of emissions
2020 SCIENTIFIC REPORTS
Vol. 10(1) 
article DOI  
Abstract: Methane (CH4) is emitted from lakes by several processes: bubbles
released from bottom sediments that reach the atmosphere (ebullition);
spring release of CH4 trapped in bubbles in and under the ice during
fall freeze (bubble release), and diffusion of CH4 from sediments to the
surface. Each of these emission routes is highly variable over space and
time, and episodic in the extreme, making reliable measurements
difficult to carry out. However, lakes are receiving increasing interest
for their important contribution to global CH4 emissions. Their area,
distribution and emissions respond to interannual and longer-term
climate fluctuations and close to half the world's lake area is in high
northern latitudes that are experiencing rapidly-warming temperatures
and lengthening thaw periods. We report on a new spatially-explicit data
set of lakes >50 degrees N, classified with methane-relevant criteria.
The seasonality of daily CH4 fluxes is driven with satellite
observations of thaw timing and duration. We found that observed thaw
seasons are 10-30% shorter than those assumed in previous studies. The
area of lakes is 1,095x10(3) km(2) and total CH4 emission is 13.8-17.7
Tg CH4 year(-1): 11.2-14.4 Tg via diffusion and ebullition and 2.6-3.3
Tg from spring release of CH4 stored in bubbles in winter lake ice. This
novel suite of data and methodologies provides a unique framework to
model CH4 emission from lakes under current, past and future climates.
BibTeX:
@article{WOS:000556875200009,
  author = {Matthews, E. and Johnson, Matthew S. and Genovese, V. and Du, J. and
Bastviken, D.}, title = {Methane emission from high latitude lakes: methane-centric lake
classification and satellite-driven annual cycle of emissions}, journal = {SCIENTIFIC REPORTS}, year = {2020}, volume = {10}, number = {1}, doi = {https://doi.org/10.1038/s41598-020-68246-1} }
Engram, M., Anthony, K.M.W., Sachs, T., Kohnert, K., Serafimovich, A., Grosse, G. and Meyer, F.J. Remote sensing northern lake methane ebullition 2020 NATURE CLIMATE CHANGE
Vol. 10(6), pp. 511+ 
article DOI  
Abstract: Northern lakes are considered a major source of atmospheric methane
(CH4), a potent GHG(1,2). However, large uncertainties in their
emissions (7-26 Tg CH4 yr(-1); ref. (2)) arise from challenges in
upscaling field data, including fluxes by ebullition (bubbling), the
dominant emission pathway(2). Remote sensing of ebullition would allow
detailed mapping of regional emissions but has hitherto not been
developed. Here, we show that lake ebullition can be imaged using
synthetic aperture radar remote sensing during ice-cover periods by
exploiting the effect of ebullition on the texture of the ice-water
interface. Applying this method to five Alaska regions and combining
spatial remote sensing information with year-round bubble-trap flux
measurements, we create ebullition-flux maps for 5,143 Alaskan lakes.
Regional lake CH4 emissions, based on satellite remote sensing analyses,
were lower compared to previous estimates based on upscaling from
individual lakes(2,3) and were consistent with independent airborne CH4
observations. Thermokarst lakes formed by thaw of organic-rich
permafrost had the highest fluxes, although lake density and lake size
distributions also controlled regional emissions. This new remote
sensing approach offers an opportunity to improve knowledge about Arctic
CH4 fluxes and helps to explain long-standing discrepancies between
estimates of CH4 emissions from atmospheric measurements and data
upscaled from individual lakes.
Arctic lake methane emissions, which occur primarily by ebullition, are
difficult to quantify from extrapolating in situ data due to spatial and
temporal variability. Remote sensing can detect ebullition, through
changes in frozen lake surface properties, reducing uncertainty in
emission fluxes.
BibTeX:
@article{WOS:000531795100002,
  author = {Engram, M. and Anthony, K. M. Walter and Sachs, T. and Kohnert, K. and
Serafimovich, A. and Grosse, G. and Meyer, F. J.}, title = {Remote sensing northern lake methane ebullition}, journal = {NATURE CLIMATE CHANGE}, year = {2020}, volume = {10}, number = {6}, pages = {511+}, doi = {https://doi.org/10.1038/s41558-020-0762-8} }
Koffi, E.N., Bergamaschi, P., Alkama, R. and Cescatti, A. An observation-constrained assessment of the climate sensitivity and
future trajectories of wetland methane emissions
2020 SCIENCE ADVANCES
Vol. 6(15) 
article DOI  
Abstract: Wetlands are a major source of methane (CH4) and contribute between 30
and 40% to the total CH4 emissions. Wetland CH4 emissions depend on
temperature, water table depth, and both the quantity and quality of
organic matter. Global warming will affect these three drivers of
methanogenesis, raising questions about the feedbacks between natural
methane production and climate change. Until present the large-scale
response of wetland CH4 emissions to climate has been investigated with
land-surface models that have produced contrasting results. Here, we
produce a novel global estimate of wetland methane emissions based on
atmospheric inverse modeling of CH4 fluxes and observed temperature and
precipitation. Our data-driven model suggests that by 2100, current
emissions may increase by 50% to 80%, which is within the range of
50% and 150% reported in previous studies. This finding highlights the
importance of limiting global warming below 2 degrees C to avoid
substantial climate feedbacks driven by methane emissions from natural
wetlands.
BibTeX:
@article{WOS:000525751400014,
  author = {Koffi, Ernest N. and Bergamaschi, Peter and Alkama, Romain and Cescatti,
Alessandro}, title = {An observation-constrained assessment of the climate sensitivity and
future trajectories of wetland methane emissions}, journal = {SCIENCE ADVANCES}, year = {2020}, volume = {6}, number = {15}, doi = {https://doi.org/10.1126/sciadv.aay4444} }
McCalley, C.K. Methane-eating microbes 2020 NATURE CLIMATE CHANGE
Vol. 10(4), pp. 275-276 
article DOI  
BibTeX:
@article{WOS:000522381600003,
  author = {McCalley, Carmody K.},
  title = {Methane-eating microbes},
  journal = {NATURE CLIMATE CHANGE},
  year = {2020},
  volume = {10},
  number = {4},
  pages = {275-276},
  doi = {https://doi.org/10.1038/s41558-020-0736-x}
}
Oh, Y., Zhuang, Q., Liu, L., Welp, L.R., Lau, M.C.Y., Onstott, T.C., Medvigy, D., Bruhwiler, L., Dlugokencky, E.J., Hugelius, G., D'Imperio, L. and Elberling, B. Reduced net methane emissions due to microbial methane oxidation in a
warmer Arctic
2020 NATURE CLIMATE CHANGE
Vol. 10(4), pp. 317+ 
article DOI  
Abstract: Methane emissions from organic-rich soils in the Arctic have been
extensively studied due to their potential to increase the atmospheric
methane burden as permafrost thaws(1-3). However, this methane source
might have been overestimated without considering high-affinity
methanotrophs (HAMs; methane-oxidizing bacteria) recently identified in
Arctic mineral soils(4-7). Herein we find that integrating the dynamics
of HAMs and methanogens into a biogeochemistry model(8-10) that includes
permafrost soil organic carbon dynamics(3) leads to the upland methane
sink doubling (similar to 5.5 Tg CH4 yr(-1)) north of 50 degrees N in
simulations from 2000-2016. The increase is equivalent to at least half
of the difference in net methane emissions estimated between
process-based models and observation-based inversions(11,12), and the
revised estimates better match site-level and regional
observations(5,7,13-15). The new model projects doubled wetland methane
emissions between 2017-2100 due to more accessible permafrost
carbon(16-18). However, most of the increase in wetland emissions is
offset by a concordant increase in the upland sink, leading to only an
18% increase in net methane emission (from 29 to 35 Tg CH4 yr(-1)). The
projected net methane emissions may decrease further due to different
physiological responses between HAMs and methanogens in response to
increasing temperature(19,20).
BibTeX:
@article{WOS:000522381600001,
  author = {Oh, Youmi and Zhuang, Qianlai and Liu, Licheng and Welp, Lisa R. and
Lau, Maggie C. Y. and Onstott, Tullis C. and Medvigy, David and
Bruhwiler, Lori and Dlugokencky, Edward J. and Hugelius, Gustaf and
D'Imperio, Ludovica and Elberling, Bo}, title = {Reduced net methane emissions due to microbial methane oxidation in a
warmer Arctic}, journal = {NATURE CLIMATE CHANGE}, year = {2020}, volume = {10}, number = {4}, pages = {317+}, doi = {https://doi.org/10.1038/s41558-020-0734-z} }
Ganesan, A.L., Schwietzke, S., Poulter, B., Arnold, T., Lan, X., Rigby, M., Vogel, F.R., van der Werf, G.R., Janssens-Maenhout, G., Boesch, H., Pandey, S., Manning, A.J., Jackson, R.B., Nisbet, E.G. and Manning, M. Advancing Scientific Understanding of the Global Methane Budget in
Support of the Paris Agreement
2019 GLOBAL BIOGEOCHEMICAL CYCLES
Vol. 33(12), pp. 1475-1512 
article DOI  
Abstract: The 2015 Paris Agreement of the United Nations Framework Convention on
Climate Change aims to keep global average temperature increases well
below 2 degrees C of preindustrial levels in the Year 2100. Vital to its
success is achieving a decrease in the abundance of atmospheric methane
(CH4), the second most important anthropogenic greenhouse gas. If this
reduction is to be achieved, individual nations must make and meet
reduction goals in their nationally determined contributions, with
regular and independently verifiable global stock taking. Targets for
the Paris Agreement have been set, and now the capability must follow to
determine whether CH4 reductions are actually occurring. At present,
however, there are significant limitations in the ability of scientists
to quantify CH4 emissions accurately at global and national scales and
to diagnose what mechanisms have altered trends in atmospheric mole
fractions in the past decades. For example, in 2007, mole fractions
suddenly started rising globally after a decade of almost no growth.
More than a decade later, scientists are still debating the mechanisms
behind this increase. This study reviews the main approaches and
limitations in our current capability to diagnose the drivers of changes
in atmospheric CH4 and, crucially, proposes ways to improve this
capability in the coming decade. Recommendations include the following:
(i) improvements to process-based models of the main sectors of CH4
emissions-proposed developments call for the expansion of tropical
wetland flux measurements, bridging remote sensing products for improved
measurement of wetland area and dynamics, expanding measurements of
fossil fuel emissions at the facility and regional levels, expanding
country-specific data on the composition of waste sent to landfill and
the types of wastewater treatment systems implemented, characterizing
and representing temporal profiles of crop growing seasons, implementing
parameters related to ruminant emissions such as animal feed, and
improving the detection of small fires associated with agriculture and
deforestation; (ii) improvements to measurements of CH4 mole fraction
and its isotopic variations-developments include greater vertical
profiling at background sites, expanding networks of dense urban
measurements with a greater focus on relatively poor countries,
improving the precision of isotopic ratio measurements of (CH4)-C-13,
CH3D, (CH4)-C-14, and clumped isotopes, creating isotopic reference
materials for international-scale development, and expanding spatial and
temporal characterization of isotopic source signatures; and (iii)
improvements to inverse modeling systems to derive emissions from
atmospheric measurements-advances are proposed in the areas of hydroxyl
radical quantification, in systematic uncertainty quantification through
validation of chemical transport models, in the use of source tracers
for estimating sector-level emissions, and in the development of time
and space resolved national inventories. These and other recommendations
are proposed for the major areas of CH4 science with the aim of
improving capability in the coming decade to quantify atmospheric CH4
budgets on the scales necessary for the success of climate policies.
BibTeX:
@article{WOS:000503923900001,
  author = {Ganesan, Anita L. and Schwietzke, Stefan and Poulter, Benjamin and
Arnold, Tim and Lan, Xin and Rigby, Matt and Vogel, Felix R. and van der
Werf, Guido R. and Janssens-Maenhout, Greet and Boesch, Hartmut and
Pandey, Sudhanshu and Manning, Alistair J. and Jackson, Robert B. and
Nisbet, Euan G. and Manning, Martin}, title = {Advancing Scientific Understanding of the Global Methane Budget in
Support of the Paris Agreement}, journal = {GLOBAL BIOGEOCHEMICAL CYCLES}, year = {2019}, volume = {33}, number = {12}, pages = {1475-1512}, doi = {https://doi.org/10.1029/2018GB006065} }
Schaefer, H. On the Causes and Consequences of Recent Trends in Atmospheric Methane 2019 CURRENT CLIMATE CHANGE REPORTS
Vol. 5(4), pp. 259-274 
article DOI  
Abstract: Purpose of Review To investigate which processes cause the current
increase in atmospheric methane in the context of future interactions
between climate change, the methane cycle and policy decisions.
Recent Findings There is evidence for various contributors to emission
increases or reduced removal of atmospheric methane. No single process
can explain the methane rise and remain consistent with available data.
Reconstructions of recent changes in the methane budget do not converge
as to the dominant contributor to the rise. A plausible scenario
includes increasing emissions from agriculture and fossil fuels while
biomass burning is reduced, with possible contributions from wetlands
and a weakened sink.
Summary Further studies are needed to identify contributors to the
methane rise for targeted emission reductions and adaptation to changes
in natural methane sources and sinks. Mitigation plans must address the
methane rise and possible consequences from a climate-methane feedback.
BibTeX:
@article{WOS:000517127500001,
  author = {Schaefer, Hinrich},
  title = {On the Causes and Consequences of Recent Trends in Atmospheric Methane},
  journal = {CURRENT CLIMATE CHANGE REPORTS},
  year = {2019},
  volume = {5},
  number = {4},
  pages = {259-274},
  doi = {https://doi.org/10.1007/s40641-019-00140-z}
}
Thornton, B.F., Geibel, M.C., Crill, P.M., Humborg, C. and Morth, C.-M. Comment on ``Understanding the Permafrost-Hydrate System and Associated
Methane Releases in the East Siberian Arctic Shelf''
2019 GEOSCIENCES
Vol. 9(9) 
article DOI  
Abstract: The recent paper in Geosciences, ``Understanding the Permafrost-Hydrate
System and Associated Methane Releases in the East Siberian Arctic
Shelf'' by Shakhova, Semiletov, and Chuvilin, (henceforth
``S2019''), contains a number of false statements about our 2016
paper, ``Methane fluxes from the sea to the atmosphere across the
Siberian shelf seas'', (henceforth ``T2016''). S2019 use three
paragraphs of section 5 of their paper to claim methodological errors
and issues in T2016. Notably they claim that in T2016, we systematically
removed data outliers including data with high methane concentrations;
this claim is false. While we appreciate that flawed methodologies can
be a problem in any area of science, in this case, the claims made in
S2019 are simply false. In this comment, we detail the incorrect claims
made in S2019 regarding T2016, and then discuss some additional
problematic aspects of S2019.
BibTeX:
@article{WOS:000487634500022,
  author = {Thornton, Brett F. and Geibel, Marc C. and Crill, Patrick M. and
Humborg, Christoph and Morth, Carl-Magnus}, title = {Comment on ``Understanding the Permafrost-Hydrate System and Associated
Methane Releases in the East Siberian Arctic Shelf''}, journal = {GEOSCIENCES}, year = {2019}, volume = {9}, number = {9}, doi = {https://doi.org/10.3390/geosciences9090384} }
Peltola, O., Vesala, T., Gao, Y., Raty, O., Alekseychik, P., Aurela, M., Chojnicki, B., Desai, A.R., Dolman, A.J., Euskirchen, E.S., Friborg, T., Goeckede, M., Helbig, M., Humphreys, E., Jackson, R.B., Jocher, G., Joos, F., Klatt, J., Knox, S.H., Kowalska, N., Kutzbach, L., Lienert, S., Lohila, A., Mammarella, I., Nadeau, D.F., Nilsson, M.B., Oechel, W.C., Peichl, M., Pypker, T., Quinton, W., Rinne, J., Sachs, T., Samson, M., Schmid, H.P., Sonnentag, O., Wille, C., Zona, D. and Aalto, T. Monthly gridded data product of northern wetland methane emissions based
on upscaling eddy covariance observations
2019 EARTH SYSTEM SCIENCE DATA
Vol. 11(3), pp. 1263-1289 
article DOI  
Abstract: Natural wetlands constitute the largest and most uncertain source of
methane (CH4) to the atmosphere and a large fraction of them are found
in the northern latitudes. These emissions are typically estimated using
process (''bottom-up'') or inversion (''top-down'') models.
However, estimates from these two types of models are not independent of
each other since the top-down estimates usually rely on the a priori
estimation of these emissions obtained with process models. Hence,
independent spatially explicit validation data are needed. Here we
utilize a random forest (RF) machine-learning technique to upscale CH4
eddy covariance flux measurements from 25 sites to estimate CH4 wetland
emissions from the northern latitudes (north of 45 degrees N). Eddy
covariance data from 2005 to 2016 are used for model development. The
model is then used to predict emissions during 2013 and 2014. The
predictive performance of the RF model is evaluated using a
leave-one-site-out cross-validation scheme. The performance
(Nash-Sutcliffe model efficiency = 0.47) is comparable to previous
studies upscaling net ecosystem exchange of carbon dioxide and studies
comparing process model output against site-level CH4 emission data. The
global distribution of wetlands is one major source of uncertainty for
upscaling CH4. Thus, three wetland distribution maps are utilized in the
upscaling. Depending on the wetland distribution map, the annual
emissions for the northern wetlands yield 32 (22.3-41.2, 95% confidence
interval calculated from a RF model ensemble), 31 (21.4-39.9) or 38
(25.9-49.5) Tg(CH4) yr(-1). To further evaluate the uncertainties of the
upscaled CH4 flux data products we also compared them against output
from two process models (LPX-Bern and WetCHARTs), and methodological
issues related to CH4 flux upscaling are discussed. The monthly upscaled
CH4 flux data products are available at
https://doi.org/10.5281/zenodo.2560163.
BibTeX:
@article{WOS:000482519900001,
  author = {Peltola, Olli and Vesala, Timo and Gao, Yao and Raty, Olle and
Alekseychik, Pavel and Aurela, Mika and Chojnicki, Bogdan and Desai,
Ankur R. and Dolman, Albertus J. and Euskirchen, Eugenie S. and Friborg,
Thomas and Goeckede, Mathias and Helbig, Manuel and Humphreys, Elyn and
Jackson, Robert B. and Jocher, Georg and Joos, Fortunat and Klatt,
Janina and Knox, Sara H. and Kowalska, Natalia and Kutzbach, Lars and
Lienert, Sebastian and Lohila, Annalea and Mammarella, Ivan and Nadeau,
Daniel F. and Nilsson, Mats B. and Oechel, Walter C. and Peichl,
Matthias and Pypker, Thomas and Quinton, William and Rinne, Janne and
Sachs, Torsten and Samson, Mateusz and Schmid, Hans Peter and Sonnentag,
Oliver and Wille, Christian and Zona, Donatella and Aalto, Tuula}, title = {Monthly gridded data product of northern wetland methane emissions based
on upscaling eddy covariance observations}, journal = {EARTH SYSTEM SCIENCE DATA}, year = {2019}, volume = {11}, number = {3}, pages = {1263-1289}, doi = {https://doi.org/10.5194/essd-11-1263-2019} }
Ishizawa, M., Chan, D., Worthy, D., Chan, E., Vogel, F. and Maksyutov, S. Analysis of atmospheric CH4 in Canadian Arctic and estimation
of the regional CH4 fluxes
2019 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 19(7), pp. 4637-4658 
article DOI  
Abstract: The Canadian Arctic (> 60 degrees N, 60-141 degrees W) may undergo
drastic changes if the Arctic warming trend continues. For methane
(CH4), Arctic reservoirs are large and widespread, and the climate
feedbacks from such changes may be potentially substantial. Current
bottom-up and top-down estimates of the regional CH4 flux range widely.
This study analyzes the recent observations of atmospheric CH4 from five
arctic monitoring sites and presents estimates of the regional CH4
fluxes for 2012-2015. The observational data reveal sizeable synoptic
summertime enhancements in the atmospheric CH4 that are distinguishable
from background variations, which indicate strong regional fluxes
(primarily wetland and biomass burning CH4 emissions) around Behchoko
and Inuvik in the western Canadian Arctic. Three regional Bayesian
inversion modelling systems with two Lagrangian particle dispersion
models and three meteorological datasets are applied to estimate fluxes
for the Canadian Arctic and show relatively robust results in amplitude
and temporal variations across different transport models, prior fluxes,
and subregion masking. The estimated mean total CH4 flux for the entire
Canadian Arctic is 1.8 +/- 0.6 Tg CH4 yr(-1). The flux estimate is
partitioned into biomass burning of 0.3 +/- 0.1 Tg CH4 yr(-1) and the
remaining natural (wetland) flux of 1.5 +/- 0.5 Tg CH4 yr(-1). The
summer natural CH4 flux estimates clearly show inter-annual variability
that is positively correlated with surface temperature anomalies. The
results indicate that years with warmer summer conditions result in more
wetland CH4 emissions. More data and analysis are required to
statistically characterize the dependence of regional CH4 fluxes on the
climate in the Arctic. These Arctic measurement sites will aid in
quantifying the inter-annual variations and long-term trends in CH4
emissions in the Canadian Arctic.
BibTeX:
@article{WOS:000463861600004,
  author = {Ishizawa, Misa and Chan, Douglas and Worthy, Doug and Chan, Elton and
Vogel, Felix and Maksyutov, Shamil}, title = {Analysis of atmospheric CH4 in Canadian Arctic and estimation
of the regional CH4 fluxes}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2019}, volume = {19}, number = {7}, pages = {4637-4658}, doi = {https://doi.org/10.5194/acp-19-4637-2019} }
Miller, S.M., Michalak, A.M., Detmers, R.G., Hasekamp, O.P., Bruhwiler, L.M.P. and Schwietzke, S. China's coal mine methane regulations have not curbed growing emissions 2019 NATURE COMMUNICATIONS
Vol. 10 
article DOI  
Abstract: Anthropogenic methane emissions from China are likely greater than in
any other country in the world. The largest fraction of China's
anthropogenic emissions is attributable to coal mining, but these
emissions may be changing; China enacted a suite of regulations for coal
mine methane (CMM) drainage and utilization that came into full effect
in 2010. Here, we use methane observations from the GOSAT satellite to
evaluate recent trends in total anthropogenic and natural emissions from
Asia with a particular focus on China. We find that emissions from China
rose by 1.1 +/- 0.4 Tg CH(4)yr(-1) from 2010 to 2015, culminating in
total anthropogenic and natural emissions of 61.5 +/- 2.7 Tg CH4 in
2015. The observed trend is consistent with pre-2010 trends and is
largely attributable to coal mining. These results indicate that China's
CMM regulations have had no discernible impact on the continued increase
in Chinese methane emissions.
BibTeX:
@article{WOS:000456957900001,
  author = {Miller, Scot M. and Michalak, Anna M. and Detmers, Robert G. and
Hasekamp, Otto P. and Bruhwiler, Lori M. P. and Schwietzke, Stefan}, title = {China's coal mine methane regulations have not curbed growing emissions}, journal = {NATURE COMMUNICATIONS}, year = {2019}, volume = {10}, doi = {https://doi.org/10.1038/s41467-018-07891-7} }
Tsuruta, A., Aalto, T., Backman, L., Krol, M.C., Peters, W., Lienert, S., Joos, F., Miller, P.A., Zhang, W., Laurila, T., Hatakka, J., Leskinen, A., Lehtinen, K.E.J., Peltola, O., Vesala, T., Levula, J., Dlugokencky, E., Heimann, M., Kozlova, E., Aurela, M., Lohila, A., Kauhaniemi, M. and Gomez-Pelaez, A.J. Methane budget estimates in Finland from the CarbonTracker
Europe-CH4 data assimilation system
2019 TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
Vol. 71 
article DOI  
Abstract: We estimated the CH4 budget in Finland for 2004-2014 using the CTE-CH4
data assimilation system with an extended atmospheric CH4 observation
network of seven sites from Finland to surrounding regions (Hyytiala,
Kjolnes, Kumpula, Pallas, Puijo, Sodankyla, and Uto). The estimated
average annual total emission for Finland is 0.6 +/- 0.5 Tg CH4 yr(-1).
Sensitivity experiments show that the posterior biospheric emission
estimates for Finland are between 0.3 and 0.9 Tg CH4 yr(-1), which lies
between the LPX-Bern-DYPTOP (0.2 Tg CH4 yr(-1)) and LPJG-WHyMe (2.2 Tg
CH4 yr(-1)) process-based model estimates. For anthropogenic emissions,
we found that the EDGAR v4.2 FT2010 inventory (0.4 Tg CH4 yr(-1)) is
likely to overestimate emissions in southernmost Finland, but the extent
of overestimation and possible relocation of emissions are difficult to
derive from the current observation network. The posterior emission
estimates were especially reliant on prior information in central
Finland. However, based on analysis of posterior atmospheric CH4, we
found that the anthropogenic emission distribution based on a national
inventory is more reliable than the one based on EDGAR v4.2 FT2010. The
contribution of total emissions in Finland to global total emissions is
only about 0.13%, and the derived total emissions in Finland showed no
trend during 2004-2014. The model using optimized emissions was able to
reproduce observed atmospheric CH4 at the sites in Finland and
surrounding regions fairly well (correlation > 0.75, bias < +/- 7 ppb),
supporting adequacy of the observations to be used in atmospheric
inversion studies. In addition to global budget estimates, we found that
CTE-CH4 is also applicable for regional budget estimates, where small
scale (1 degrees x1 degrees in this case) optimization is possible with
a dense observation network.
BibTeX:
@article{WOS:000498977700001,
  author = {Tsuruta, Aki and Aalto, Tuula and Backman, Leif and Krol, Maarten C. and
Peters, Wouter and Lienert, Sebastian and Joos, Fortunat and Miller,
Paul A. and Zhang, Wenxin and Laurila, Tuomas and Hatakka, Juha and
Leskinen, Ari and Lehtinen, Kari E. J. and Peltola, Olli and Vesala,
Timo and Levula, Janne and Dlugokencky, Ed and Heimann, Martin and
Kozlova, Elena and Aurela, Mika and Lohila, Annalea and Kauhaniemi, Mari
and Gomez-Pelaez, Angel J.}, title = {Methane budget estimates in Finland from the CarbonTracker
Europe-CH4 data assimilation system}, journal = {TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY}, year = {2019}, volume = {71}, doi = {https://doi.org/10.1080/16000889.2018.1565030} }
van Huissteden, J. Methane and Biogenic Volatile Organic Compound Emissions in Eastern
Siberia
2019
Vol. 236WATER-CARBON DYNAMICS IN EASTERN SIBERIA, pp. 101-134 
incollection DOI  
BibTeX:
@incollection{WOS:000778471200006,
  author = {van Huissteden, Jacobus},
  title = {Methane and Biogenic Volatile Organic Compound Emissions in Eastern
Siberia}, booktitle = {WATER-CARBON DYNAMICS IN EASTERN SIBERIA}, year = {2019}, volume = {236}, pages = {101-134}, doi = {https://doi.org/10.1007/978-981-13-6317-7_5} }
Dimdore-Miles, O.B., Palmer, P.I. and Bruhwiler, L.P. Detecting changes in Arctic methane emissions: limitations of the
inter-polar difference of atmospheric mole fractions
2018 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 18(24), pp. 17895-17907 
article DOI  
Abstract: We consider the utility of the annual inter-polar difference (IPD) as a
metric for changes in Arctic emissions of methane (CH4). The IPD has
been previously defined as the difference between weighted annual means
of CH4 mole fraction data collected at stations from the two polar
regions (defined as latitudes poleward of 53 degrees N and 53 degrees S,
respectively). This subtraction approach (IPD) implicitly assumes that
extra-polar CH4 emissions arrive within the same calendar year at both
poles. We show using a continuous version of the IPD that the metric
includes not only changes in Arctic emissions but also terms that
represent atmospheric transport of air masses from lower latitudes to
the polar regions. We show the importance of these atmospheric transport
terms in understanding the IPD using idealized numerical experiments
with the TM5 global 3-D atmospheric chemistry transport model that is
run from 1980 to 2010. A northern mid-latitude pulse in January 1990,
which increases prior emission distributions, arrives at the Arctic with
a higher mole fraction and similar or equal to 12 months earlier than at
the Antarctic. The perturbation at the poles subsequently decays with an
e-folding lifetime of similar or equal to 4 years. A similarly timed
pulse emitted from the tropics arrives with a higher value at the
Antarctic similar or equal to 11 months earlier than at the Arctic. This
perturbation decays with an e-folding lifetime of similar or equal to 7
years. These simulations demonstrate that the assumption of symmetric
transport of extra-polar emissions to the poles is not realistic,
resulting in considerable IPD variations due to variations in emissions
and atmospheric transport. We assess how well the annual IPD can detect
a constant annual growth rate of Arctic emissions for three scenarios,
0.5 %, 1 %, and 2 %, superimposed on signals from lower latitudes,
including random noise. We find that it can take up to 16 years to
detect the smallest prescribed trend in Arctic emissions at the 95%
confidence level. Scenarios with higher, but likely unrealistic, growth
in Arctic emissions are detected in less than a decade. We argue that a
more reliable measurement-driven approach would require data collected
from all latitudes, emphasizing the importance of maintaining a global
monitoring network to observe decadal changes in atmospheric greenhouse
gases.
BibTeX:
@article{WOS:000453427000003,
  author = {Dimdore-Miles, Oscar B. and Palmer, Paul I. and Bruhwiler, Lori P.},
  title = {Detecting changes in Arctic methane emissions: limitations of the
inter-polar difference of atmospheric mole fractions}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2018}, volume = {18}, number = {24}, pages = {17895-17907}, doi = {https://doi.org/10.5194/acp-18-17895-2018} }
Treat, C.C., Marushchak, M.E., Voigt, C., Zhang, Y., Tan, Z., Zhuang, Q., Virtanen, T.A., Rasanen, A., Biasi, C., Hugelius, G., Kaverin, D., Miller, P.A., Stendel, M., Romanovsky, V., Rivkin, F., Martikainen, P.J. and Shurpali, N.J. Tundra landscape heterogeneity, not interannual variability, controls
the decadal regional carbon balance in the Western Russian Arctic
2018 GLOBAL CHANGE BIOLOGY
Vol. 24(11), pp. 5188-5204 
article DOI  
Abstract: Across the Arctic, the net ecosystem carbon (C) balance of tundra
ecosystems is highly uncertain due to substantial temporal variability
of C fluxes and to landscape heterogeneity. We modeled both carbon
dioxide (CO2) and methane (CH4) fluxes for the dominant land cover types
in a similar to 100-km(2) sub-Arctic tundra region in northeast European
Russia for the period of 2006-2015 using process-based biogeochemical
models. Modeled net annual CO2 fluxes ranged from --300 g C m(-2)
year(-1) [net uptake] in a willow fen to 3 g Cm-2 year(-1) [net
source] in dry lichen tundra. Modeled annual CH4 emissions ranged from
-0.2 to 22.3 g Cm-2 year(-1) at a peat plateau site and a willow fen
site, respectively. Interannual variability over the decade was
relatively small (20%-25%) in comparison with variability among the
land cover types (150%). Using high-resolution land cover
classification, the region was a net sink of atmospheric CO2 across most
land cover types but a net source of CH4 to the atmosphere due to high
emissions from permafrost-free fens. Using a lower resolution for land
cover classification resulted in a 20%-65% underestimation of regional
CH4 flux relative to high-resolution classification and smaller (10%)
overestimation of regional CO2 uptake due to the underestimation of
wetland area by 60%. The relative fraction of uplands versus wetlands
was key to determining the net regional C balance at this and other
Arctic tundra sites because wetlands were hot spots for C cycling in
Arctic tundra ecosystems.
BibTeX:
@article{WOS:000447760300016,
  author = {Treat, Claire C. and Marushchak, Maija E. and Voigt, Carolina and Zhang,
Yu and Tan, Zeli and Zhuang, Qianlai and Virtanen, Tarmo A. and Rasanen,
Aleksi and Biasi, Christina and Hugelius, Gustaf and Kaverin, Dmitry and
Miller, Paul A. and Stendel, Martin and Romanovsky, Vladimir and Rivkin,
Felix and Martikainen, Pertti J. and Shurpali, Narasinha J.}, title = {Tundra landscape heterogeneity, not interannual variability, controls
the decadal regional carbon balance in the Western Russian Arctic}, journal = {GLOBAL CHANGE BIOLOGY}, year = {2018}, volume = {24}, number = {11}, pages = {5188-5204}, doi = {https://doi.org/10.1111/gcb.14421} }
Lin, X., Ciais, P., Bousquet, P., Ramonet, M., Yin, Y., Balkanski, Y., Cozic, A., Delmotte, M., Evangeliou, N., Indira, N.K., Locatelli, R., Peng, S., Piao, S., Saunois, M., Swathi, P.S., Wang, R., Yver-Kwok, C., Tiwari, Y.K. and Zhou, L. Simulating CH4 and CO2 over South and East Asia
using the zoomed chemistry transport model LMDz-INCA
2018 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 18(13), pp. 9475-9497 
article DOI  
Abstract: The increasing availability of atmospheric measurements of greenhouse
gases (GHGs) from surface stations can improve the retrieval of their
fluxes at higher spatial and temporal resolutions by inversions,
provided that transport models are able to properly represent the
variability of concentrations observed at different stations. South and
East Asia (SEA; the study area in this paper including the regions of
South Asia and East Asia) is a region with large and very uncertain
emissions of carbon dioxide (CO2) and methane (CH4), the most potent
anthropogenic GHGs. Monitoring networks have expanded greatly during the
past decade in this region, which should contribute to reducing
uncertainties in estimates of regional GHG budgets. In this study, we
simulate concentrations of CH4 and CO2 using zoomed versions
(abbreviated as ``ZAs'') of the global chemistry transport model
LMDz-INCA, which have fine horizontal resolutions of similar to 0.66
degrees in longitude and similar to 0.51 degrees in latitude over SEA
and coarser resolutions elsewhere. The concentrations of CH4 and CO2
simulated from ZAs are compared to those from the same model but with
standard model grids of 2.50 degrees in longitude and 1.27 degrees in
latitude (abbreviated as ``STs''), both prescribed with the same
natural and anthropogenic fluxes. Model performance is evaluated for
each model version at multi-annual, seasonal, synoptic and diurnal
scales, against a unique observation dataset including 39 global and
regional stations over SEA and around the world. Results show that ZAs
improve the overall representation of CH4 annual gradients between
stations in SEA, with reduction of RMSE by 16-20% compared to STs. The
model improvement mainly results from reduction in representation error
at finer horizontal resolutions and thus better characterization of the
CH4 concentration gradients related to scattered distributed emission
sources. However, the performance of ZAs at a specific station as
compared to STs is more sensitive to errors in meteorological forcings
and surface fluxes, especially when short-term variabilities or stations
close to source regions are examined. This highlights the importance of
accurate a priori CH4 surface fluxes in high-resolution transport
modeling and inverse studies, particularly regarding locations and
magnitudes of emission hotspots. Model performance for CO2 suggests that
the CO2 surface fluxes have not been prescribed with sufficient accuracy
and resolution, especially the spatiotemporally varying carbon exchange
between land surface and atmosphere. In addition, the representation of
the CH4 and CO2 short-term variabilities is also limited by model's
ability to simulate boundary layer mixing and mesoscale transport in
complex terrains, emphasizing the need to improve sub-grid physical
parameterizations in addition to refinement of model resolutions.
BibTeX:
@article{WOS:000437733900003,
  author = {Lin, Xin and Ciais, Philippe and Bousquet, Philippe and Ramonet, Michel
and Yin, Yi and Balkanski, Yves and Cozic, Anne and Delmotte, Marc and
Evangeliou, Nikolaos and Indira, Nuggehalli K. and Locatelli, Robin and
Peng, Shushi and Piao, Shilong and Saunois, Marielle and Swathi,
Panangady S. and Wang, Rong and Yver-Kwok, Camille and Tiwari, Yogesh K.
and Zhou, Lingxi}, title = {Simulating CH4 and CO2 over South and East Asia
using the zoomed chemistry transport model LMDz-INCA}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2018}, volume = {18}, number = {13}, pages = {9475-9497}, doi = {https://doi.org/10.5194/acp-18-9475-2018} }
Tadic, J.M. and Biraud, S.C. An Approach to Estimate Atmospheric Greenhouse Gas Total Columns Mole
Fraction from Partial Column Sampling
2018 ATMOSPHERE
Vol. 9(7) 
article DOI  
Abstract: This study presents a new conceptual approach to estimate total column
mole fractions of CO2 and CH4 using partial column data. It provides a
link between airborne in situ and remote sensing observations of
greenhouse gases. The method relies on in situ observations, external
ancillary sources of information (e.g., atmospheric transport models),
and a regression kriging framework. We evaluate our new approach using
National Oceanic and Atmospheric Administration's (NOAA's) AirCore
program-in situ vertical profiles of CO2 and CH4 collected from weather
balloons. Our paper shows that under the specific conditions of this
study and assumption of unbiasedness, airborne observations up to
6500-9500 m altitude are required to achieve comparable total column CO2
mole fraction uncertainty as the Total Carbon Column Observing Network
(TCCON) network provides, given as a precision of the ratio between
observed and true total column-integrated mole fraction, assuming 400
ppm XCO2 (2 sigma, e.g., 0.8 ppm). If properly calibrated, our approach
could be applied to vertical profiles of CO2 collected from aircraft
using a few flask samples, while retaining similar uncertainty level.
Our total column CH4 estimates, by contrast, are less accurate than
TCCON's. Aircrafts are not as spatially constrained as TCCON ground
stations, so our approach adds value to aircraft-based vertical profiles
for evaluating remote sensing platforms.
BibTeX:
@article{WOS:000445141400011,
  author = {Tadic, Jovan M. and Biraud, Sebastien C.},
  title = {An Approach to Estimate Atmospheric Greenhouse Gas Total Columns Mole
Fraction from Partial Column Sampling}, journal = {ATMOSPHERE}, year = {2018}, volume = {9}, number = {7}, doi = {https://doi.org/10.3390/atmos9070247} }
Feldman, D.R., Collins, W.D., Biraud, S.C., Risser, M.D., Turner, D.D., Gero, P.J., Tadic, J., Helmig, D., Xie, S., Mlawer, E.J., Shippert, T.R. and Torn, M.S. Observationally derived rise in methane surface forcing mediated by
water vapour trends
2018 NATURE GEOSCIENCE
Vol. 11(4), pp. 238+ 
article DOI  
Abstract: Atmospheric methane (CH4) mixing ratios exhibited a plateau between 1995
and 2006 and have subsequently been increasing. While there are a number
of competing explanations for the temporal evolution of this greenhouse
gas, these prominent features in the temporal trajectory of atmospheric
CH4 are expected to perturb the surface energy balance through radiative
forcing, largely due to the infrared radiative absorption features of
CH4. However, to date this has been determined strictly through
radiative transfer calculations. Here, we present a quantified
observation of the time series of clear-sky radiative forcing by CH4 at
the surface from 2002 to 2012 at a single site derived from
spectroscopic measurements along with line-by-line calculations using
ancillary data. There was no significant trend in CH4 forcing between
2002 and 2006, but since then, the trend in forcing was 0.026 +/- 0.006
(99.7% CI) W m(2) yr(-1). The seasonal-cycle amplitude and secular
trends in observed forcing are influenced by a corresponding seasonal
cycle and trend in atmospheric CH4. However, we find that we must
account for the overlapping absorption effects of atmospheric water
vapour (H2O) and CH4 to explain the observations fully. Thus, the
determination of CH4 radiative forcing requires accurate observations of
both the spatiotemporal distribution of CH4 and the vertically resolved
trends in H2O.
BibTeX:
@article{WOS:000429131600014,
  author = {Feldman, D. R. and Collins, W. D. and Biraud, S. C. and Risser, M. D.
and Turner, D. D. and Gero, P. J. and Tadic, J. and Helmig, D. and Xie,
S. and Mlawer, E. J. and Shippert, T. R. and Torn, M. S.}, title = {Observationally derived rise in methane surface forcing mediated by
water vapour trends}, journal = {NATURE GEOSCIENCE}, year = {2018}, volume = {11}, number = {4}, pages = {238+}, doi = {https://doi.org/10.1038/s41561-018-0085-9} }
Dean, J.F., Middelburg, J.J., Rockmann, T., Aerts, R., Blauw, L.G., Egger, M., Jetten, M.S.M., de Jong, A.E.E., Meisel, O.H., Rasigraf, O., Slomp, C.P., in't Zandt, M.H. and Dolman, A.J. Methane Feedbacks to the Global Climate System in a Warmer World 2018 REVIEWS OF GEOPHYSICS
Vol. 56(1), pp. 207-250 
article DOI  
Abstract: Methane (CH4) is produced in many natural systems that are vulnerable to
change under a warming climate, yet current CH4 budgets, as well as
future shifts in CH4 emissions, have high uncertainties. Climate change
has the potential to increase CH4 emissions from critical systems such
as wetlands, marine and freshwater systems, permafrost, and methane
hydrates, through shifts in temperature, hydrology, vegetation,
landscape disturbance, and sea level rise. Increased CH4 emissions from
these systems would in turn induce further climate change, resulting in
a positive climate feedback. Here we synthesize biological, geochemical,
and physically focused CH4 climate feedback literature, bringing
together the key findings of these disciplines. We discuss
environment-specific feedback processes, including the microbial,
physical, and geochemical interlinkages and the timescales on which they
operate, and present the current state of knowledge of CH4 climate
feedbacks in the immediate and distant future. The important linkages
between microbial activity and climate warming are discussed with the
aim to better constrain the sensitivity of the CH4 cycle to future
climate predictions. We determine that wetlands will form the majority
of the CH4 climate feedback up to 2100. Beyond this timescale, CH4
emissions from marine and freshwater systems and permafrost environments
could become more important. Significant CH4 emissions to the atmosphere
from the dissociation of methane hydrates are not expected in the near
future. Our key findings highlight the importance of quantifying whether
CH4 consumption can counterbalance CH4 production under future climate
scenarios.
Plain Language Summary
Methane is a powerful greenhouse gas, second only to carbon dioxide in
its importance to climate change. Methane production in natural
environments is controlled by factors that are themselves influenced by
climate. Increased methane production can warm the Earth, which can in
turn cause methane to be produced at a faster rate - this is called a
positive climate feedback. Here we describe the most important natural
environments for methane production that have the potential to produce a
positive climate feedback. We discuss how these feedbacks may develop in
the coming centuries under predicted climate warming using a
cross-disciplinary approach. We emphasize the importance of considering
methane dynamics at all scales, especially its production and
consumption and the role microorganisms play in both these processes, to
our understanding of current and future global methane emissions.
Marrying large-scale geophysical studies with site-scale biogeochemical
and microbial studies will be key to this.
BibTeX:
@article{WOS:000430130800007,
  author = {Dean, Joshua F. and Middelburg, Jack J. and Rockmann, Thomas and Aerts,
Rien and Blauw, Luke G. and Egger, Matthias and Jetten, Mike S. M. and
de Jong, Anniek E. E. and Meisel, Ove H. and Rasigraf, Olivia and Slomp,
Caroline P. and in't Zandt, Michiel H. and Dolman, A. J.}, title = {Methane Feedbacks to the Global Climate System in a Warmer World}, journal = {REVIEWS OF GEOPHYSICS}, year = {2018}, volume = {56}, number = {1}, pages = {207-250}, doi = {https://doi.org/10.1002/2017RG000559} }
Feinberg, A.I., Coulon, A., Stenke, A., Schwietzke, S. and Peter, T. Isotopic source signatures: Impact of regional variability on the
δ13CH4 trend and spatial distribution
2018 ATMOSPHERIC ENVIRONMENT
Vol. 174, pp. 99-111 
article DOI  
Abstract: The atmospheric methane growth rate has fluctuated over the past three
decades, signifying variations in methane sources and sinks. Methane
isotopic ratios (delta(CH4)-C-13) differ between emission categories,
and can therefore be used to distinguish which methane sources have
changed. However, isotopic modelling studies have mainly focused on
uncertainties in methane emissions rather than uncertainties in isotopic
source signatures. We simulated atmospheric delta(CH4)-C-13 for the
period 1990-2010 using the global chemistry-climate model SOCOL.
Empirically-derived regional variability in the isotopic signatures was
introduced in a suite of sensitivity simulations. These simulations were
compared to a baseline simulation with commonly used global mean
isotopic signatures. We investigated coal, natural gas/oil, wetland,
livestock, and biomass burning source signatures to determine whether
regional variations impact the observed isotopic trend and spatial
distribution. Based on recently published source signature datasets, our
calculated global mean isotopic signatures are in general lighter than
the commonly used values. Trends in several isotopic signatures were
also apparent during the period 1990-2010. Tropical livestock emissions
grew during the 2000s, introducing isotopically heavier livestock
emissions since tropical livestock consume more C-4 vegetation than
midlatitude livestock. Chinese coal emissions, which are isotopically
heavy compared to other coals, increase during the 2000s leading to
higher global values of delta(CH4)-C-13 for coal emissions. EDGAR v4.2
emissions disagree with the observed atmospheric isotopic trend for
almost all simulations, confirming past doubts about this emissions
inventory. The agreement between the modelled and observed
delta(CH4)-C-13 interhemispheric differences improves when regional
source signatures are used. Even though the simulated results are highly
dependent on the choice of methane emission inventories, they emphasize
that the commonly used global mean signatures are inadequate. Regional
isotopic signatures should be employed in modelling studies that try to
constrain methane emission inventories.
BibTeX:
@article{WOS:000423888400010,
  author = {Feinberg, Aryeh I. and Coulon, Ancelin and Stenke, Andrea and
Schwietzke, Stefan and Peter, Thomas}, title = {Isotopic source signatures: Impact of regional variability on the
δ13CH4 trend and spatial distribution}, journal = {ATMOSPHERIC ENVIRONMENT}, year = {2018}, volume = {174}, pages = {99-111}, doi = {https://doi.org/10.1016/j.atmosenv.2017.11.037} }
Hoesly, R.M., Smith, S.J., Feng, L., Klimont, Z., Janssens-Maenhout, G., Pitkanen, T., Seibert, J.J., Vu, L., Andres, R.J., Bolt, R.M., Bond, T.C., Dawidowski, L., Kholod, N., Kurokawa, J.-i., Li, M., Liu, L., Lu, Z., Moura, M.C.P., O'Rourke, P.R. and Zhang, Q. Historical (1750-2014) anthropogenic emissions of reactive gases and
aerosols from the Community Emissions Data System (CEDS)
2018 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 11(1), pp. 369-408 
article DOI  
Abstract: We present a new data set of annual historical (1750-2014) anthropogenic
chemically reactive gases (CO, CH4, NH3, NOx, SO2, NMVOCs), carbonaceous
aerosols (black carbon - BC, and organic carbon - OC), and CO2 developed
with the Community Emissions Data System (CEDS). We improve upon
existing inventories with a more consistent and reproducible methodology
applied to all emission species, updated emission factors, and recent
estimates through 2014. The data system relies on existing energy
consumption data sets and regional and country-specific inventories to
produce trends over recent decades. All emission species are
consistently estimated using the same activity data over all time
periods. Emissions are provided on an annual basis at the level of
country and sector and gridded with monthly seasonality. These estimates
are comparable to, but generally slightly higher than, existing global
inventories. Emissions over the most recent years are more uncertain,
particularly in low-and middle-income regions where country-specific
emission inventories are less available. Future work will involve
refining and updating these emission estimates, estimating emissions'
uncertainty, and publication of the system as open-source software.
BibTeX:
@article{WOS:000423507000001,
  author = {Hoesly, Rachel M. and Smith, Steven J. and Feng, Leyang and Klimont,
Zbigniew and Janssens-Maenhout, Greet and Pitkanen, Tyler and Seibert,
Jonathan J. and Linh Vu and Andres, Robert J. and Bolt, Ryan M. and
Bond, Tami C. and Dawidowski, Laura and Kholod, Nazar and Kurokawa,
June-ichi and Li, Meng and Liu, Liang and Lu, Zifeng and Moura, Maria
Cecilia P. and O'Rourke, Patrick R. and Zhang, Qiang}, title = {Historical (1750-2014) anthropogenic emissions of reactive gases and
aerosols from the Community Emissions Data System (CEDS)}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2018}, volume = {11}, number = {1}, pages = {369-408}, doi = {https://doi.org/10.5194/gmd-11-369-2018} }
van der Velde, I.R., Miller, J.B., van der Molen, M.K., Tans, P.P., Vaughn, B.H., White, J.W.C., Schaefer, K. and Peters, W. The CarbonTracker Data Assimilation System for CO2 and
δ13C (CTDAS-C13 v1.0): retrieving information on
land-atmosphere exchange processes
2018 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 11(1), pp. 283-304 
article DOI  
Abstract: To improve our understanding of the global carbon balance and its
representation in terrestrial biosphere models, we present here a first
dual-species application of the CarbonTracker Data Assimilation System
(CTDAS). The system's modular design allows for assimilating multiple
atmospheric trace gases simultaneously to infer exchange fluxes at the
Earth surface. In the prototype discussed here, we interpret signals
recorded in observed carbon dioxide (CO2) along with observed ratios of
its stable isotopologues (CO2)-C-13/(CO2)-C-12 (delta C-13). The latter
is in particular a valuable tracer to untangle CO2 exchange from land
and oceans. Potentially, it can also be used as a proxy for
continent-wide drought stress in plants, largely because the ratio of
(CO2)-C-13 and (CO2)-C-12 molecules removed from the atmosphere by
plants is dependent on moisture conditions. The dual-species CTDAS
system varies the net exchange fluxes of both (CO2)-C-13 and CO2 in
ocean and terrestrial biosphere models to create an ensemble of
(CO2)-C-13 and CO2 fluxes that propagates through an atmospheric
transport model. Based on differences between observed and simulated
(CO2)-C-13 and CO2 mole fractions (and thus delta C-13) our Bayesian
minimization approach solves for weekly adjustments to both net fluxes
and isotopic terrestrial discrimination that minimizes the difference
between observed and estimated mole fractions.
With this system, we are able to estimate changes in terrestrial delta
C-13 exchange on seasonal and continental scales in the Northern
Hemisphere where the observational network is most dense. Our results
indicate a decrease in stomatal conductance on a continent-wide scale
during a severe drought. These changes could only be detected after
applying combined atmospheric CO2 and delta C-13 constraints as done in
this work. The additional constraints on surface CO2 exchange from delta
C-13 observations neither affected the estimated carbon fluxes nor
compromised our ability to match observed CO2 variations. The prototype
presented here can be of great benefit not only to study the global
carbon balance but also to potentially function as a data-driven
diagnostic to assess multiple leaf-level exchange parameterizations in
carbon-climate models that influence the CO2, water, isotope, and energy
balance.
BibTeX:
@article{WOS:000423149900001,
  author = {van der Velde, Ivar R. and Miller, John B. and van der Molen, Michiel K.
and Tans, Pieter P. and Vaughn, Bruce H. and White, James W. C. and
Schaefer, Kevin and Peters, Wouter}, title = {The CarbonTracker Data Assimilation System for CO2 and
δ13C (CTDAS-C13 v1.0): retrieving information on
land-atmosphere exchange processes}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2018}, volume = {11}, number = {1}, pages = {283-304}, doi = {https://doi.org/10.5194/gmd-11-283-2018} }
Hartery, S., Commane, R., Lindaas, J., Sweeney, C., Henderson, J., Mountain, M., Steiner, N., McDonald, K., Dinardo, S.J., Miller, C.E., Wofsy, S.C. and Chang, R.Y.W. Estimating regional-scale methane flux and budgets using CARVE aircraft
measurements over Alaska
2018 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 18(1), pp. 185-202 
article DOI  
Abstract: Methane (CH4) is the second most important greenhouse gas but its
emissions from northern regions are still poorly constrained. In this
study, we analyze a subset of in situ CH4 aircraft observations made
over Alaska during the growing seasons of 2012-2014 as part of the
Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE). Net
surface CH4 fluxes are estimated using a Lagrangian particle dispersion
model which quantitatively links surface emissions from Alaska and the
western Yukon with observations of enhanced CH4 in the mixed layer. We
estimate that between May and September, net CH4 emissions from the
region of interest were 2.2 +/- 0.5 Tg, 1.9 +/- 0.4 Tg, and 2.3 +/- 0.6
Tg of CH4 for 2012, 2013, and 2014, respectively. If emissions are only
attributed to two biogenic eco-regions within our domain, then tundra
regions were the predominant source, accounting for over half of the
overall budget despite only representing 18% of the total surface area.
Bo-real regions, which cover a large part of the study region, accounted
for the remainder of the emissions. Simple multiple linear regression
analysis revealed that, overall, CH4 fluxes were largely driven by soil
temperature and elevation. In regions specifically dominated by
wetlands, soil temperature and moisture at 10 cm depth were important
explanatory variables while in regions that were not wetlands, soil
temperature and moisture at 40 cm depth were more important, suggesting
deeper methanogenesis in drier soils. Although similar environmental
drivers have been found in the past to control CH4 emissions at local
scales, this study shows that they can be used to generate a statistical
model to estimate the regional-scale net CH4 budget.
BibTeX:
@article{WOS:000419530300002,
  author = {Hartery, Sean and Commane, Roisin and Lindaas, Jakob and Sweeney, Colm
and Henderson, John and Mountain, Marikate and Steiner, Nicholas and
McDonald, Kyle and Dinardo, Steven J. and Miller, Charles E. and Wofsy,
Steven C. and Chang, Rachel Y. -W.}, title = {Estimating regional-scale methane flux and budgets using CARVE aircraft
measurements over Alaska}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2018}, volume = {18}, number = {1}, pages = {185-202}, doi = {https://doi.org/10.5194/acp-18-185-2018} }
White, J.W.C., Allen, D., Amar, P.K., Bogner, J., Bruhwiler, L., Cooley, D., Frankenberg, C., George, F., Hanle, L., Hristov, A.H., Kebreab, E., Leytem, A., Mastalerz, M., Wofsy, S., Ravishankara, A.R., Chen, S.S., Bitz, C., Cane, M.A., Cullen, H., Dunbar, R., Emch, P., Fiore, A., Frumhoff, P., Gail, W.B., Glackin, M., Hogue, T.S., Joseph, E., Keener Jr., R.N., Kopp, R., Leung, L.R., Overpeck, J., Steiner, A., Titley, D.W., Waliser, D., Methane, C.A., Climate, B.A.S., Resources, B.A.N., Resources, B.E.S., Syst, B.E.E., Toxicology, B.E.S., Studies, D.E.L., Sci, N.A., Engn, N.A. and Med, N.A. Improving Characterization of Anthropogenic Methane Emissions in the
United States Preface
2018 IMPROVING CHARACTERIZATION OF ANTHROPOGENIC METHANE EMISSIONS IN THE
UNITED STATES, pp. XI+ 
incollection  
BibTeX:
@incollection{WOS:000568964900001,
  author = {White, James W. C. and Allen, David and Amar, Praveen K. and Bogner,
Jean and Bruhwiler, Lori and Cooley, Daniel and Frankenberg, Christian
and George, Fiji and Hanle, Lisa and Hristov, Alexander H. and Kebreab,
Ermias and Leytem, April and Mastalerz, Maria and Wofsy, Steven and
Ravishankara, A. R. and Chen, Shuyi S. and Bitz, Cecilia and Cane, Mark
A. and Cullen, Heidi and Dunbar, Robert and Emch, Pamela and Fiore,
Arlene and Frumhoff, Peter and Gail, William B. and Glackin, Mary and
Hogue, Terri S. and Joseph, Everette and Keener, Jr., Ronald Nick and
Kopp, Robert and Leung, L. Ruby and Overpeck, Jonathan and Steiner,
Allison and Titley, David W. and Waliser, Duane and Comm Anthropogenic
Methane and Board Atmospheric Sci Climate and Board Agr Nat Resources
and Board Earth Sci Resources and Board Energy Environm Syst and Board
Environm Studies Toxicology and Div Earth Life Studies and Natl Acad Sci
and Natl Acad Engn and Natl Acad Med}, title = {Improving Characterization of Anthropogenic Methane Emissions in the
United States Preface}, booktitle = {IMPROVING CHARACTERIZATION OF ANTHROPOGENIC METHANE EMISSIONS IN THE
UNITED STATES}, year = {2018}, pages = {XI+} }
Saunois, M., Bousquet, P., Poulter, B., Peregon, A., Ciais, P., Canadell, J.G., Dlugokencky, E.J., Etiope, G., Bastviken, D., Houweling, S., Janssens-Maenhout, G., Tubiello, F.N., Castaldi, S., Jackson, R.B., Alexe, M., Arora, V.K., Beerling, D.J., Bergamaschi, P., Blake, D.R., Brailsford, G., Bruhwiler, L., Crevoisier, C., Crill, P., Covey, K., Frankenberg, C., Gedney, N., Hoeglund-Isaksson, L., Ishizawa, M., Ito, A., Joos, F., Kim, H.-S., Kleinen, T., Krummel, P., Lamarque, J.-F., Langenfelds, R., Locatelli, R., Machida, T., Maksyutov, S., Melton, J.R., Morino, I., Naik, V., O'Doherty, S., Parmentier, F.-J., Patra, P.K., Peng, C., Peng, S., Peters, G.P., Pison, I., Prinn, R., Ramonet, M., Riley, W.J., Saito, M., Santini, M., Schroeder, R., Simpson, I.J., Spahni, R., Takizawa, A., Thornton, B.F., Tian, H., Tohjima, Y., Viovy, N., Voulgarakis, A., Weiss, R., Wilton, D.J., Wiltshire, A., Worthy, D., Wunch, D., Xu, X., Yoshida, Y., Zhang, B., Zhang, Z. and Zhu, Q. Variability and quasi-decadal changes in the methane budget over the
period 2000-2012
2017 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 17(18), pp. 11135-11161 
article DOI  
Abstract: Following the recent Global Carbon Project (GCP) synthesis of the
decadal methane (CH4) budget over 2000-2012 (Saunois et al., 2016), we
analyse here the same dataset with a focus on quasi-decadal and
inter-annual variability in CH4 emissions. The GCP dataset integrates
results from top-down studies (exploiting atmospheric observations
within an atmospheric inverse-modelling framework) and bottom-up models
(including process-based models for estimating land surface emissions
and atmospheric chemistry), inventories of anthropogenic emissions, and
data-driven approaches.
The annual global methane emissions from top-down studies, which by
construction match the observed methane growth rate within their
uncertainties, all show an increase in total methane emissions over the
period 2000-2012, but this increase is not linear over the 13 years.
Despite differences between individual studies, the mean emission
anomaly of the top-down ensemble shows no significant trend in total
methane emissions over the period 2000-2006, during the plateau of
atmospheric methane mole fractions, and also over the period 2008-2012,
during the renewed atmospheric methane increase. However, the top-down
ensemble mean produces an emission shift between 2006 and 2008, leading
to 22 [16-32] Tg CH4 yr(-1) higher methane emissions over the period
2008-2012 compared to 2002-2006. This emission increase mostly
originated from the tropics, with a smaller contribution from
mid-latitudes and no significant change from boreal regions.
The regional contributions remain uncertain in top-down studies.
Tropical South America and South and East Asia seem to contribute the
most to the emission increase in the tropics. However, these two regions
have only limited atmospheric measurements and remain therefore poorly
constrained.
The sectorial partitioning of this emission increase between the periods
2002-2006 and 2008-2012 differs from one atmospheric inversion study to
another. However, all top-down studies suggest smaller changes in fossil
fuel emissions (from oil, gas, and coal industries) compared to the mean
of the bottom-up inventories included in this study. This difference is
partly driven by a smaller emission change in China from the top-down
studies compared to the estimate in the Emission Database for Global
Atmospheric Research (EDGARv4.2) inventory, which should be revised to
smaller values in a near future. We apply isotopic signatures to the
emission changes estimated for individual studies based on five emission
sectors and find that for six individual top-down studies (out of eight)
the average isotopic signature of the emission changes is not consistent
with the observed change in atmospheric (CH4)-C-13. However, the
partitioning in emission change derived from the ensemble mean is
consistent with this isotopic constraint. At the global scale, the
top-down ensemble mean suggests that the dominant contribution to the
resumed atmospheric CH4 growth after 2006 comes from microbial sources
(more from agriculture and waste sectors than from natural wetlands),
with an uncertain but smaller contribution from fossil CH4 emissions. In
addition, a decrease in biomass burning emissions (in agreement with the
biomass burning emission databases) makes the balance of sources
consistent with atmospheric (CH4)-C-13 observations.
In most of the top-down studies included here, OH concentrations are
considered constant over the years (seasonal variations but without any
inter-annual variability). As a result, the methane loss (in particular
through OH oxidation) varies mainly through the change in methane
concentrations and not its oxidants. For these reasons, changes in the
methane loss could not be properly investigated in this study, although
it may play a significant role in the recent atmospheric methane changes
as briefly discussed at the end of the paper.
BibTeX:
@article{WOS:000411253700003,
  author = {Saunois, Marielle and Bousquet, Philippe and Poulter, Ben and Peregon,
Anna and Ciais, Philippe and Canadell, Josep G. and Dlugokencky, Edward
J. and Etiope, Giuseppe and Bastviken, David and Houweling, Sander and
Janssens-Maenhout, Greet and Tubiello, Francesco N. and Castaldi, Simona
and Jackson, Robert B. and Alexe, Mihai and Arora, Vivek K. and
Beerling, David J. and Bergamaschi, Peter and Blake, Donald R. and
Brailsford, Gordon and Bruhwiler, Lori and Crevoisier, Cyril and Crill,
Patrick and Covey, Kristofer and Frankenberg, Christian and Gedney,
Nicola and Hoeglund-Isaksson, Lena and Ishizawa, Misa and Ito, Akihiko
and Joos, Fortunat and Kim, Heon-Sook and Kleinen, Thomas and Krummel,
Paul and Lamarque, Jean-Francois and Langenfelds, Ray and Locatelli,
Robin and Machida, Toshinobu and Maksyutov, Shamil and Melton, Joe R.
and Morino, Isamu and Naik, Vaishali and O'Doherty, Simon and
Parmentier, Frans-JanW. and Patra, Prabir K. and Peng, Changhui and
Peng, Shushi and Peters, Glen P. and Pison, Isabelle and Prinn, Ronald
and Ramonet, Michel and Riley, William J. and Saito, Makoto and Santini,
Monia and Schroeder, Ronny and Simpson, Isobel J. and Spahni, Renato and
Takizawa, Atsushi and Thornton, Brett F. and Tian, Hanqin and Tohjima,
Yasunori and Viovy, Nicolas and Voulgarakis, Apostolos and Weiss, Ray
and Wilton, David J. and Wiltshire, Andy and Worthy, Doug and Wunch,
Debra and Xu, Xiyan and Yoshida, Yukio and Zhang, Bowen and Zhang, Zhen
and Zhu, Qiuan}, title = {Variability and quasi-decadal changes in the methane budget over the
period 2000-2012}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2017}, volume = {17}, number = {18}, pages = {11135-11161}, doi = {https://doi.org/10.5194/acp-17-11135-2017} }
Poulter, B., Bousquet, P., Canadell, J.G., Ciais, P., Peregon, A., Saunois, M., Arora, V.K., Beerling, D.J., Brovkin, V., Jones, C.D., Joos, F., Gedney, N., Ito, A., Kleinen, T., Koven, C.D., McDonald, K., Melton, J.R., Peng, C., Peng, S., Prigent, C., Schroeder, R., Riley, W.J., Saito, M., Spahni, R., Tian, H., Taylor, L., Viovy, N., Wilton, D., Wiltshire, A., Xu, X., Zhang, B., Zhang, Z. and Zhu, Q. Global wetland contribution to 2000-2012 atmospheric methane growth rate
dynamics
2017 ENVIRONMENTAL RESEARCH LETTERS
Vol. 12(9) 
article DOI  
Abstract: Increasing atmospheric methane (CH4) concentrations have contributed to
approximately 20% of anthropogenic climate change. Despite the
importance of CH4 as a greenhouse gas, its atmospheric growth rate and
dynamics over the past two decades, which include a stabilization period
(1999-2006), followed by renewed growth starting in 2007, remain poorly
understood. We provide an updated estimate of CH4 emissions from
wetlands, the largest natural global CH4 source, for 2000-2012 using an
ensemble of biogeochemical models constrained with remote sensing
surface inundation and inventory-based wetland area data. Between
2000-2012, boreal wetland CH4 emissions increased by 1.2 Tg yr(-1)
(-0.2-3.5 Tg yr(-1)), tropical emissions decreased by 0.9 Tg yr(-1)
(-3.2-1.1 Tg yr(-1)), yet globally, emissions remained unchanged at 184
+/- 22 Tg yr(-1). Changing air temperature was responsible for
increasing high-latitude emissions whereas declines in low-latitude
wetland area decreased tropical emissions; both dynamics are consistent
with features of predicted centennial-scale climate change impacts on
wetland CH4 emissions. Despite uncertainties in wetland area mapping,
our study shows that global wetland CH4 emissions have not contributed
significantly to the period of renewed atmospheric CH4 growth, and is
consistent with findings from studies that indicate some combination of
increasing fossil fuel and agriculture-related CH4 emissions, and a
decrease in the atmospheric oxidative sink.
BibTeX:
@article{WOS:000410925500001,
  author = {Poulter, Benjamin and Bousquet, Philippe and Canadell, Josep G. and
Ciais, Philippe and Peregon, Anna and Saunois, Marielle and Arora, Vivek
K. and Beerling, David J. and Brovkin, Victor and Jones, Chris D. and
Joos, Fortunat and Gedney, Nicola and Ito, Akihito and Kleinen, Thomas
and Koven, Charles D. and McDonald, Kyle and Melton, Joe R. and Peng,
Changhui and Peng, Shushi and Prigent, Catherine and Schroeder, Ronny
and Riley, William J. and Saito, Makoto and Spahni, Renato and Tian,
Hanqin and Taylor, Lyla and Viovy, Nicolas and Wilton, David and
Wiltshire, Andy and Xu, Xiyan and Zhang, Bowen and Zhang, Zhen and Zhu,
Qiuan}, title = {Global wetland contribution to 2000-2012 atmospheric methane growth rate
dynamics}, journal = {ENVIRONMENTAL RESEARCH LETTERS}, year = {2017}, volume = {12}, number = {9}, doi = {https://doi.org/10.1088/1748-9326/aa8391} }
Thonat, T., Saunois, M., Bousquet, P., Pison, I., Tan, Z., Zhuang, Q., Crill, P.M., Thornton, B.F., Bastviken, D., Dlugokencky, E.J., Zimov, N., Laurila, T., Hatakka, J., Hermansen, O. and Worthy, D.E.J. Detectability of Arctic methane sources at six sites performing
continuous atmospheric measurements
2017 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 17(13), pp. 8371-8394 
article DOI  
Abstract: Understanding the recent evolution of methane emissions in the Arctic is
necessary to interpret the global methane cycle. Emissions are affected
by significant uncertainties and are sensitive to climate change,
leading to potential feedbacks. A polar version of the CHIMERE
chemistry-transport model is used to simulate the evolution of
tropospheric methane in the Arctic during 2012, including all known
regional anthropogenic and natural sources, in particular freshwater
emissions which are often overlooked in methane modelling. CHIMERE
simulations are compared to atmospheric continuous observations at six
measurement sites in the Arctic region. In winter, the Arctic is
dominated by anthropogenic emissions; emissions from continental
seepages and oceans, including from the East Siberian Arctic Shelf, can
contribute significantly in more limited areas. In summer, emissions
from wetland and freshwater sources dominate across the whole region.
The model is able to reproduce the seasonality and synoptic variations
of methane measured at the different sites. We find that all methane
sources significantly affect the measurements at all stations at least
at the synoptic scale, except for biomass burning. In particular,
freshwater systems play a decisive part in summer, representing on
average between 11 and 26% of the simulated Arctic methane signal at
the sites. This indicates the relevance of continuous observations to
gain a mechanistic understanding of Arctic methane sources. Sensitivity
tests reveal that the choice of the land-surface model used to prescribe
wetland emissions can be critical in correctly representing methane
mixing ratios. The closest agreement with the observations is reached
when using the two wetland models which have emissions peaking in
August-September, while all others reach their maximum in JuneJuly. Such
phasing provides an interesting constraint on wetland models which still
have large uncertainties at present. Also testing different freshwater
emission inventories leads to large differences in modelled methane.
Attempts to include methane sinks (OH oxidation and soil uptake) reduced
the model bias relative to observed atmospheric methane. The study
illustrates how multiple sources, having different spatiotemporal
dynamics and magnitudes, jointly influence the overall Arctic methane
budget, and highlights ways towards further improved assessments.
BibTeX:
@article{WOS:000405372800001,
  author = {Thonat, Thibaud and Saunois, Marielle and Bousquet, Philippe and Pison,
Isabelle and Tan, Zeli and Zhuang, Qianlai and Crill, Patrick M. and
Thornton, Brett F. and Bastviken, David and Dlugokencky, Ed J. and
Zimov, Nikita and Laurila, Tuomas and Hatakka, Juha and Hermansen, Ove
and Worthy, Doug E. J.}, title = {Detectability of Arctic methane sources at six sites performing
continuous atmospheric measurements}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2017}, volume = {17}, number = {13}, pages = {8371-8394}, doi = {https://doi.org/10.5194/acp-17-8371-2017} }
Schwietzke, S., Petron, G., Conley, S., Pickering, C., Mielke-Maday, I., Dlugokencky, E.J., Tans, P.P., Vaughn, T., Bell, C., Zimmerle, D., Wolter, S., King, C.W., White, A.B., Coleman, T., Bianco, L. and Schnell, R.C. Improved Mechanistic Understanding of Natural Gas Methane Emissions from
Spatially Resolved Aircraft Measurements
2017 ENVIRONMENTAL SCIENCE &amp; TECHNOLOGY
Vol. 51(12), pp. 7286-7294 
article DOI  
Abstract: Divergence in recent oil and gas related methane emission estimates
between aircraft studies (basin total for a midday window) and emissions
inventories (annualized regional and national statistics) indicate the
need for better understanding the experimental design, including
temporal and spatial alignment and interpretation of results. Our
aircraft-based methane emission estimates in a major U.S. shale gas
basin resolved from west to east show (i) similar spatial distributions
for 2 days, (ii) strong spatial correlations with reported NG production
(R-2 = 0.75) and active gas well pad count (R-2 = 0.81), and (iii) 2x
higher emissions in the western half (normalized by gas production)
despite relatively homogeneous dry gas and well characteristics.
Operator reported hourly activity data show that midday episodic
emissions from manual liquid unloadings (a routine operation in this
basin and elsewhere) could explain similar to 1/3 of the total emissions
detected midday by the aircraft and similar to 2/3 of the west east
difference in emissions. The 22% emission difference between both days
further emphasizes that episodic sources can substantially impact midday
methane emissions and that aircraft may detect daily peak emissions
rather than daily averages that are generally employed in emissions
inventories. While the aircraft approach is valid, quantitative, and
independent, our study sheds new light on the interpretation of previous
basin scale aircraft studies, and provides an improved mechanistic
understanding of oil and gas related methane emissions.
BibTeX:
@article{WOS:000404087400072,
  author = {Schwietzke, Stefan and Petron, Gabrielle and Conley, Stephen and
Pickering, Cody and Mielke-Maday, Ingrid and Dlugokencky, Edward J. and
Tans, Pieter P. and Vaughn, Tim and Bell, Clay and Zimmerle, Daniel and
Wolter, Sonja and King, Clark W. and White, Allen B. and Coleman,
Timothy and Bianco, Laura and Schnell, Russell C.}, title = {Improved Mechanistic Understanding of Natural Gas Methane Emissions from
Spatially Resolved Aircraft Measurements}, journal = {ENVIRONMENTAL SCIENCE &amp; TECHNOLOGY}, year = {2017}, volume = {51}, number = {12}, pages = {7286-7294}, doi = {https://doi.org/10.1021/acs.est.7b01810} }
Peters, C.N., Bennartz, R. and Hornberger, G.M. Satellite-derived methane emissions from inundation in Bangladesh 2017 JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Vol. 122(5), pp. 1137-1155 
article DOI  
Abstract: The uncertainty in methane (CH4) source strength of rice fields and
wetlands is particularly high in South Asia CH4 budgets. We used
satellite observations of CH4 column mixing ratios from Atmospheric
Infrared Sounder (AIRS), Scanning Imaging Absorption Spectrometer for
Atmospheric Chartography (SCIAMACHY), and Greenhouse Gases Observing
Satellite (GOSAT) to estimate the contribution of Bangladesh emissions
to atmospheric CH4 concentrations. Using satellite-derived inundation
area as a proxy for source area, we developed a simple inverse advection
model that estimates average annual CH4 surface fluxes to be 4, 9, and
19mgCH(4)m(-2)h(-1) in AIRS, SCIAMACHY, and GOSAT, respectively. Despite
this variability, our flux estimates varied over a significantly
narrower range than reported values for CH4 surface fluxes from a survey
of 32 studies reporting ground-based observations between 0 and
260mgCH(4)m(-2)h(-1). Upscaling our satellite-derived surface flux
estimates, we estimated total annual CH4 emissions for Bangladesh to be
1.33.2, 1.82.0, 3.11.6Tgyr(-1), depending on the satellite. Our
estimates of total emissions are in line with the median of total
emission values for Bangladesh reported in earlier studies.
Plain Language Summary The extent of methane emissions from flooded
areas, such as wetlands and rice paddies, is not well understood,
particularly in South Asia. This study uses satellite observations of
atmospheric methane and flooding to explore seasonal fluctuation in
methane emissions from Bangladesh. Our findings suggest methane
emissions similar to previously thought.
BibTeX:
@article{WOS:000403487600010,
  author = {Peters, C. N. and Bennartz, R. and Hornberger, G. M.},
  title = {Satellite-derived methane emissions from inundation in Bangladesh},
  journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
  year = {2017},
  volume = {122},
  number = {5},
  pages = {1137-1155},
  doi = {https://doi.org/10.1002/2016JG003740}
}
Bruhwiler, L.M., Basu, S., Bergamaschi, P., Bousquet, P., Dlugokencky, E., Houweling, S., Ishizawa, M., Kim, H.S., Locatelli, R., Maksyutov, S., Montzka, S., Pandey, S., Patra, P.K., Petron, G., Saunois, M., Sweeney, C., Schwietzke, S., Tans, P. and Weatherhead, E.C. US CH4 emissions from oil and gas production: Have recent
large increases been detected?
2017 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 122(7), pp. 4070-4083 
article DOI  
Abstract: Recent studies have proposed significant increases in CH4 emissions
possibly from oil and gas (O&amp;G) production, especially for the U.S.
where O&amp;G production has reached historically high levels over the past
decade. In this study, we show that an ensemble of time-dependent
atmospheric inversions constrained by calibrated atmospheric
observations of surface CH4 mole fraction, with some including
space-based retrievals of column average CH4 mole fractions, suggests
that North American CH4 emissions have been flat over years spanning
2000 through 2012. Estimates of emission trends using zonal gradients of
column average CH4 calculated relative to an upstream background are not
easy to make due to atmospheric variability, relative insensitivity of
column average CH4 to surface emissions at regional scales, and fast
zonal synoptic transport. In addition, any trends in continental
enhancements of column average CH4 are sensitive to how the upstream
background is chosen, and model simulations imply that short-term
(4years or less) trends in column average CH4 horizontal gradients of up
to 1.5ppb/yr can occur just from interannual transport variability
acting on a strong latitudinal CH4 gradient. Finally, trends in spatial
gradients calculated from space-based column average CH4 can be
significantly biased (>2-3ppb/yr) due to the nonuniform and seasonally
varying temporal coverage of satellite retrievals.
Plain Language Summary In this paper we address recent claims of
significant increases in methane emissions from U.S. oil and gas
production. We find that such claims are inconsistent with observations
by examining atmospheric inversions and observations from the NOAA
aircraft monitoring program. Furthermore, we show how atmospheric
variability, sampling biases, and choice of upwind background can lead
to spurious trends in atmospheric column average methane when using both
in situ and space-based retrievals.
BibTeX:
@article{WOS:000400172000023,
  author = {Bruhwiler, L. M. and Basu, S. and Bergamaschi, P. and Bousquet, P. and
Dlugokencky, E. and Houweling, S. and Ishizawa, M. and Kim, H. -S. and
Locatelli, R. and Maksyutov, S. and Montzka, S. and Pandey, S. and
Patra, P. K. and Petron, G. and Saunois, M. and Sweeney, C. and
Schwietzke, S. and Tans, P. and Weatherhead, E. C.}, title = {US CH4 emissions from oil and gas production: Have recent
large increases been detected?}, journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, year = {2017}, volume = {122}, number = {7}, pages = {4070-4083}, doi = {https://doi.org/10.1002/2016JD026157} }
Jiang, Z., Worden, J.R., Worden, H., Deeter, M., Jones, D.B.A., Arellano, A.F. and Henze, D.K. A 15-year record of CO emissions constrained by MOPITT CO observations 2017 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 17(7), pp. 4565-4583 
article DOI  
Abstract: Long-term measurements from satellites and surface stations have
demonstrated a decreasing trend of tropospheric carbon monoxide (CO) in
the Northern Hemisphere over the past decade. Likely explanations for
this decrease include changes in anthropogenic, fires, and/or biogenic
emissions or changes in the primary chemical sink hydroxyl radical (OH).
Using remotely sensed CO measurements from the Measurement of Pollution
in the Troposphere (MOPITT) satellite instrument, in situ methyl
chloroform (MCF) measurements from the World Data Centre for Greenhouse
Gases (WDCGG) and the adjoint of the GEOS-Chem model, we estimate the
change in global CO emissions from 2001 to 2015. We show that the loss
rate of MCF varied by 0.2% in the past 15 years, indicating that
changes in global OH distributions do not explain the recent decrease in
CO. Our two-step inversion approach for estimating CO emissions is
intended to mitigate the effect of bias errors in the MOPITT data as
well as model errors in transport and chemistry, which are the primary
factors contributing to the uncertainties when quantifying CO emissions
using these remotely sensed data. Our results confirm that the
decreasing trend of tropospheric CO in the Northern Hemisphere is due to
decreasing CO emissions from anthropogenic and biomass burning sources.
In particular, we find decreasing CO emissions from the United States
and China in the past 15 years, and unchanged anthropogenic CO emissions
from Europe since 2008. We find decreasing trends of biomass burning CO
emissions from boreal North America, boreal Asia and South America, but
little change over Africa. In contrast to prior results, we find that a
positive trend in CO emissions is likely for India and southeast Asia.
BibTeX:
@article{WOS:000399401900001,
  author = {Jiang, Zhe and Worden, John R. and Worden, Helen and Deeter, Merritt and
Jones, Dylan B. A. and Arellano, Avelino F. and Henze, Daven K.}, title = {A 15-year record of CO emissions constrained by MOPITT CO observations}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2017}, volume = {17}, number = {7}, pages = {4565-4583}, doi = {https://doi.org/10.5194/acp-17-4565-2017} }
Wei, D. and Wang, X. Uncertainty and dynamics of natural wetland CH4 release in
China: Research status and priorities
2017 ATMOSPHERIC ENVIRONMENT
Vol. 154, pp. 95-105 
article DOI  
Abstract: Natural wetlands represent the largest single source of methane (CH4), a
potent greenhouse gas. China is home to the world's fourth largest
wetland area, and it is facing intense climate- and human-related
impacts. The scientific community in China has invested considerable
effort into investigating wetland CH4 release and its dynamics. Static
chamber and eddy covariance observations have verified the temperature,
water regime and air pressure as factors that regulate the diurnal and
seasonal variation of CH4 release. Non-growing seasons, especially
freezing thawing cycles, play a role in CH4 release. However, a
knowledge gap still exists with respect to the inter-annual variability
of CH4 release. Observations also suggest that water and temperature
regimes control the micro- and macro-scale spatial pattern of CH4
release, respectively. Recent bookkeeping surveys, biogeochemical model
simulations, and chemical transport model inversions, have narrowed the
uncertainty range of national CH4 release to 2.46-3.20, 2.77-4.95 and
238-4.91 Tg CH4 yr(-1), respectively. Wetland loss (especially cropland
conversion in Northeast China), despite climate changes, decreased CH4
release by 45.2%-52.2% from the 1950s-2000s, and by 13.2%-15.4% from
the 1980s-2000s. However, future warmer temperatures and rising CO2 are
predicted to strengthen national CH4 release by 32% (RCP2.6), 55%
(RCP4.5) and 91% (RCP8.5) by the 2080s, albeit without the variation in
wetland extent having been considered. Furthermore, future research
should emphasize the mechanisms involved in CH4 release during freezing
thawing cycles and interannual variability. Model data fusion of eddy
covariance and manipulative experiments, especially warming and CO2
enrichment, would benefit estimations and projections of CH4 release.
(C) 2017 Elsevier Ltd. All rights reserved.
BibTeX:
@article{WOS:000397551800009,
  author = {Wei, Da and Wang, Xiaodan},
  title = {Uncertainty and dynamics of natural wetland CH4 release in
China: Research status and priorities}, journal = {ATMOSPHERIC ENVIRONMENT}, year = {2017}, volume = {154}, pages = {95-105}, doi = {https://doi.org/10.1016/j.atmosenv.2017.01.038} }
Tsuruta, A., Aalto, T., Backman, L., Hakkarainen, J., van der Laan-Luijkx, I.T., Krol, M.C., Spahni, R., Houweling, S., Laine, M., Dlugokencky, E., Gomez-Pelaez, A.J., van der Schoot, M., Langenfelds, R., Ellul, R., Arduini, J., Apadula, F., Gerbig, C., Feist, D.G., Kivi, R., Yoshida, Y. and Peters, W. Global methane emission estimates for 2000-2012 from CarbonTracker
Europe-CH4 v1.0
2017 GEOSCIENTIFIC MODEL DEVELOPMENT
Vol. 10(3) 
article DOI  
Abstract: We present a global distribution of surface methane (CH4) emission
estimates for 2000-2012 derived using the CarbonTracker Europe-CH4
(CTE-CH4) data assimilation system. In CTE-CH4, anthropogenic and
biospheric CH4 emissions are simultaneously estimated based on
constraints of global atmospheric in situ CH4 observations. The system
was configured to either estimate only anthropogenic or biospheric
sources per region, or to estimate both categories simultaneously. The
latter increased the number of optimizable parameters from 62 to 78. In
addition, the differences between two numerical schemes available to
perform turbulent vertical mixing in the atmospheric transport model TM5
were examined. Together, the system configurations encompass important
axes of uncertainty in inversions and allow us to examine the robustness
of the flux estimates. The posterior emission estimates are further
evaluated by comparing simulated atmospheric CH4 to surface in situ
observations, vertical profiles of CH4 made by aircraft, remotely sensed
dry-air total column-averaged mole fraction (XCH4) from the Total Carbon
Column Observing Network (TCCON), and XCH4 from the Greenhouse gases
Observing Satellite (GOSAT). The evaluation with non-assimilated
observations shows that posterior XCH4 is better matched with the
retrievals when the vertical mixing scheme with faster interhemispheric
exchange is used. Estimated posterior mean total global emissions during
2000-2012 are 516 +/- 51 Tg CH4 yr(-1), with an increase of 18 Tg CH4
yr(-1) from 2000-2006 to 2007-2012. The increase is mainly driven by an
increase in emissions from South American temperate, Asian temperate and
Asian tropical TransCom regions. In addition, the increase is hardly
sensitive to different model configurations (< 2 Tg CH4 yr(-1)
difference), and much smaller than suggested by EDGAR v4.2 FT2010
inventory (33 Tg CH4 yr(-1)), which was used for prior anthropogenic
emission estimates. The result is in good agreement with other published
estimates from inverse modelling studies (16-20 Tg CH4 yr(-1)). However,
this study could not conclusively separate a small trend in biospheric
emissions (-5 to +6.9 Tg CH4 yr(-1)) from the much larger trend in
anthropogenic emissions (15-27 Tg CH4 yr(-1)). Finally, we find that the
global and North American CH4 balance could be closed over this time
period without the previously suggested need to strongly increase
anthropogenic CH4 emissions in the United States. With further
developments, especially on the treatment of the atmospheric CH4 sink,
we expect the data assimilation system presented here will be able to
contribute to the ongoing interpretation of changes in this important
greenhouse gas budget.
BibTeX:
@article{WOS:000398898800001,
  author = {Tsuruta, Aki and Aalto, Tuula and Backman, Leif and Hakkarainen, Janne
and van der Laan-Luijkx, Ingrid T. and Krol, Maarten C. and Spahni,
Renato and Houweling, Sander and Laine, Marko and Dlugokencky, Ed and
Gomez-Pelaez, Angel J. and van der Schoot, Marcel and Langenfelds, Ray
and Ellul, Raymond and Arduini, Jgor and Apadula, Francesco and Gerbig,
Christoph and Feist, Dietrich G. and Kivi, Rigel and Yoshida, Yukio and
Peters, Wouter}, title = {Global methane emission estimates for 2000-2012 from CarbonTracker
Europe-CH4 v1.0}, journal = {GEOSCIENTIFIC MODEL DEVELOPMENT}, year = {2017}, volume = {10}, number = {3}, doi = {https://doi.org/10.5194/gmd-10-1261-2017} }
Thompson, R.L., Sasakawa, M., Machida, T., Aalto, T., Worthy, D., Lavric, J.V., Myhre, C.L. and Stohl, A. Methane fluxes in the high northern latitudes for 2005-2013 estimated
using a Bayesian atmospheric inversion
2017 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 17(5), pp. 3553-3572 
article DOI  
Abstract: We present methane (CH4) flux estimates for 2005 to 2013 from a Bayesian
inversion focusing on the high northern latitudes (north of 50 degrees
N). Our inversion is based on atmospheric transport modelled by the
Lagrangian particle dispersion model FLEXPART and CH4 observations from
17 in situ and five discrete flask-sampling sites distributed over
northern North America and Eurasia. CH4 fluxes are determined at monthly
temporal resolution and on a variable grid with maximum resolution of 1
degrees x 1 degrees. Our inversion finds a CH4 source from the high
northern latitudes of 82 to 84 Tg yr(-1), constituting similar to 15%
of the global total, compared to 64 to 68 Tg yr(-1) (similar to 12 %)
in the prior estimates. For northern North America, we estimate a mean
source of 16.6 to 17.9 Tg yr(-1), which is dominated by fluxes in the
Hudson Bay Lowlands (HBL) and western Canada, specifically the province
of Alberta. Our estimate for the HBL, of 2.7 to 3.4 Tg yr(-1), is close
to the prior estimate (which includes wetland fluxes from the land
surface model, LPX-Bern) and to other independent inversion estimates.
However, our estimate for Alberta, of 5.0 to 5.8 Tg yr(-1), is
significantly higher than the prior (which also includes anthropogenic
sources from the EDGAR-4.2FT2010 inventory). Since the fluxes from this
region persist throughout the winter, this may signify that the
anthropogenic emissions are underestimated. For northern Eurasia, we
find a mean source of 52.2 to 55.5 Tg yr(-1), with a strong contribution
from fluxes in the Western Siberian Lowlands (WSL) for which we estimate
a source of 19.3 to 19.9 Tg yr(-1). Over the 9-year inversion period, we
find significant year-to-year variations in the fluxes, which in North
America, and specifically in the HBL, appear to be driven at least in
part by soil temperature, while in the WSL, the variability is more
dependent on soil moisture. Moreover, we find significant positive
trends in the CH4 fluxes in North America of 0.38 to 0.57 Tg yr(-2), and
northern Eurasia of 0.76 to 1.09 Tg yr(-2). In North America, this could
be due to an increase in soil temperature, while in North Eurasia,
specifically Russia, the trend is likely due, at least in part, to an
increase in anthropogenic sources.
BibTeX:
@article{WOS:000397827900004,
  author = {Thompson, Rona L. and Sasakawa, Motoki and Machida, Toshinobu and Aalto,
Tuula and Worthy, Doug and Lavric, Jost V. and Myhre, Cathrine Lund and
Stohl, Andreas}, title = {Methane fluxes in the high northern latitudes for 2005-2013 estimated
using a Bayesian atmospheric inversion}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2017}, volume = {17}, number = {5}, pages = {3553-3572}, doi = {https://doi.org/10.5194/acp-17-3553-2017} }
Fisher, R.E., France, J.L., Lowry, D., Lanoiselle, M., Brownlow, R., Pyle, J.A., Cain, M., Warwick, N., Skiba, U.M., Drewer, J., Dinsmore, K.J., Leeson, S.R., Bauguitte, S.J.B., Wellpott, A., O'Shea, S.J., Allen, G., Gallagher, M.W., Pitt, J., Percival, C.J., Bower, K., George, C., Hayman, G.D., Aalto, T., Lohila, A., Aurela, M., Laurila, T., Crill, P.M., McCalley, C.K. and Nisbet, E.G. Measurement of the 13C isotopic signature of methane
emissions from northern European wetlands
2017 GLOBAL BIOGEOCHEMICAL CYCLES
Vol. 31(3), pp. 605-623 
article DOI  
Abstract: Isotopic data provide powerful constraints on regional and global
methane emissions and their source profiles. However, inverse modeling
of spatially resolved methane flux is currently constrained by a lack of
information on the variability of source isotopic signatures. In this
study, isotopic signatures of emissions in the Fennoscandian Arctic have
been determined in chambers over wetland, in the air 0.3 to 3m above the
wetland surface and by aircraft sampling from 100m above wetlands up to
the stratosphere. Overall, the methane flux to atmosphere has a coherent
delta C-13 isotopic signature of -71 +/- 1%, measured in situ on the
ground in wetlands. This is in close agreement with delta C-13 isotopic
signatures of local and regional methane increments measured by aircraft
campaigns flying through air masses containing elevated methane mole
fractions. In contrast, results from wetlands in Canadian boreal forest
farther south gave isotopic signatures of -67 +/- 1%. Wetland emissions
dominate the local methane source measured over the European Arctic in
summer. Chamber measurements demonstrate a highly variable methane flux
and isotopic signature, but the results from air sampling within wetland
areas show that emissions mix rapidly immediately above the wetland
surface and methane emissions reaching the wider atmosphere do indeed
have strongly coherent C isotope signatures. The study suggests that for
boreal wetlands (>60 degrees N) global and regional modeling can use an
isotopic signature of -71 parts per thousand to apportion sources more
accurately, but there is much need for further measurements over other
wetlands regions to verify this.
BibTeX:
@article{WOS:000400695400010,
  author = {Fisher, Rebecca E. and France, James L. and Lowry, David and Lanoiselle,
Mathias and Brownlow, Rebecca and Pyle, John A. and Cain, Michelle and
Warwick, Nicola and Skiba, Ute M. and Drewer, Julia and Dinsmore, Kerry
J. and Leeson, Sarah R. and Bauguitte, Stephane J. -B. and Wellpott,
Axel and O'Shea, Sebastian J. and Allen, Grant and Gallagher, Martin W.
and Pitt, Joseph and Percival, Carl J. and Bower, Keith and George,
Charles and Hayman, Garry D. and Aalto, Tuula and Lohila, Annalea and
Aurela, Mika and Laurila, Tuomas and Crill, Patrick M. and McCalley,
Carmody K. and Nisbet, Euan G.}, title = {Measurement of the 13C isotopic signature of methane
emissions from northern European wetlands}, journal = {GLOBAL BIOGEOCHEMICAL CYCLES}, year = {2017}, volume = {31}, number = {3}, pages = {605-623}, doi = {https://doi.org/10.1002/2016GB005504} }
Bader, W., Bovy, B., Conway, S., Strong, K., Smale, D., Turner, A.J., Blumenstock, T., Boone, C., Coen, M.C., Coulon, A., Garcia, O., Griffith, D.T., Hase, F., Hausmann, P., Jones, N., Krummel, P., Murata, I., Morino, I., Nakajima, H., O'Doherty, S., Paton-Walsh, C., Robinson, J., Sandrin, R., Schneider, M., Servais, C., Sussmann, R. and Mahieu, E. The recent increase of atmospheric methane from 10 years of ground-based
NDACC FTIR observations since 2005
2017 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 17(3), pp. 2255-2277 
article DOI  
Abstract: Changes of atmospheric methane total columns (CH4) since 2005 have been
evaluated using Fourier transform infrared (FTIR) solar observations
carried out at 10 ground-based sites, affiliated to the Network for
Detection of Atmospheric Composition Change (NDACC). From this, we find
an increase of atmospheric methane total columns of 0.31 +/- 0.03%
year(-1) (2 sigma level of uncertainty) for the 2005-2014 period.
Comparisons with in situ methane measurements at both local and global
scales show good agreement. We used the GEOS-Chem chemical transport
model tagged simulation, which accounts for the contribution of each
emission source and one sink in the total methane, simulated over
2005-2012. After regridding according to NDACC vertical layering using a
conservative regridding scheme and smoothing by convolving with
respective FTIR seasonal averaging kernels, the GEOS-Chem simulation
shows an increase of atmospheric methane total columns of 0.35 +/-
0.03% year(-1) between 2005 and 2012, which is in agreement with NDACC
measurements over the same time period (0.30 +/- 0.04% year(-1),
averaged over 10 stations). Analysis of the GEOS-Chem-tagged simulation
allows us to quantify the contribution of each tracer to the global
methane change since 2005. We find that natural sources such as wetlands
and biomass burning contribute to the interannual variability of
methane. However, anthropogenic emissions, such as coal mining, and gas
and oil transport and exploration, which are mainly emitted in the
Northern Hemisphere and act as secondary contributors to the global
budget of methane, have played a major role in the increase of
atmospheric methane observed since 2005. Based on the GEOS-Chem-tagged
simulation, we discuss possible cause(s) for the increase of methane
since 2005, which is still unexplained.
BibTeX:
@article{WOS:000395118000003,
  author = {Bader, Whitney and Bovy, Benoit and Conway, Stephanie and Strong,
Kimberly and Smale, Dan and Turner, Alexander J. and Blumenstock, Thomas
and Boone, Chris and Coen, Martine Collaud and Coulon, Ancelin and
Garcia, Omaira and Griffith, DavidW. T. and Hase, Frank and Hausmann,
Petra and Jones, Nicholas and Krummel, Paul and Murata, Isao and Morino,
Isamu and Nakajima, Hideaki and O'Doherty, Simon and Paton-Walsh, Clare
and Robinson, John and Sandrin, Rodrigue and Schneider, Matthias and
Servais, Christian and Sussmann, Ralf and Mahieu, Emmanuel}, title = {The recent increase of atmospheric methane from 10 years of ground-based
NDACC FTIR observations since 2005}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2017}, volume = {17}, number = {3}, pages = {2255-2277}, doi = {https://doi.org/10.5194/acp-17-2255-2017} }
Houweling, S., Bergamaschi, P., Chevallier, F., Heimann, M., Kaminski, T., Krol, M., Michalak, A.M. and Patra, P. Global inverse modeling of CH4 sources and sinks: an overview
of methods
2017 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 17(1), pp. 235-256 
article DOI  
Abstract: The aim of this paper is to present an overview of inverse modeling
methods that have been developed over the years for estimating the
global sources and sinks of CH4. It provides insight into how techniques
and estimates have evolved over time and what the remaining shortcomings
are. As such, it serves a didactical purpose of introducing apprentices
to the field, but it also takes stock of developments so far and
reflects on promising new directions. The main focus is on
methodological aspects that are particularly relevant for CH4, such as
its atmospheric oxidation, the use of methane isotopologues, and
specific challenges in atmospheric transport modeling of CH4. The use of
satellite retrievals receives special attention as it is an active field
of methodological development, with special requirements on the sampling
of the model and the treatment of data uncertainty. Regional scale flux
estimation and attribution is still a grand challenge, which calls for
new methods capable of combining information from multiple data streams
of different measured parameters. A process model representation of
sources and sinks in atmospheric transport inversion schemes allows the
integrated use of such data. These new developments are needed not only
to improve our understanding of the main processes driving the observed
global trend but also to support international efforts to reduce
greenhouse gas emissions.
BibTeX:
@article{WOS:000392124200001,
  author = {Houweling, Sander and Bergamaschi, Peter and Chevallier, Frederic and
Heimann, Martin and Kaminski, Thomas and Krol, Maarten and Michalak,
Anna M. and Patra, Prabir}, title = {Global inverse modeling of CH4 sources and sinks: an overview
of methods}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2017}, volume = {17}, number = {1}, pages = {235-256}, doi = {https://doi.org/10.5194/acp-17-235-2017} }
Thornton, B.F., Wik, M. and Crill, P.M. Double-counting challenges the accuracy of high-latitude methane
inventories
2016 GEOPHYSICAL RESEARCH LETTERS
Vol. 43(24), pp. 12569-12577 
article DOI  
Abstract: Quantification of the present and future contribution to atmospheric
methane (CH4) from lakes, wetlands, fluvial systems, and, potentially,
coastal waters remains an important unfinished task for balancing the
global CH4 budget. Discriminating between these sources is crucial,
especially across climate-sensitive Arctic and subarctic landscapes and
waters. Yet basic underlying uncertainties remain, in such areas as
total wetland area and definitions of wetlands, which can lead to
conflation of wetlands and small ponds in regional studies. We discuss
how in situ sampling choices, remote sensing limitations, and isotopic
signature overlaps can lead to unintentional double-counting of CH4
emissions and propose that this double-counting can explain a pan-Arctic
bottom-up estimate from published sources, 59.7 Tg yr(-1) (range
36.9-89.4 Tg yr(-1)) greatly exceeding the most recent top-down inverse
modeled estimate of the pan-Arctic CH4 budget (23 +/- 5 Tg yr(-1)).
BibTeX:
@article{WOS:000392741900032,
  author = {Thornton, Brett F. and Wik, Martin and Crill, Patrick M.},
  title = {Double-counting challenges the accuracy of high-latitude methane
inventories}, journal = {GEOPHYSICAL RESEARCH LETTERS}, year = {2016}, volume = {43}, number = {24}, pages = {12569-12577}, doi = {https://doi.org/10.1002/2016GL071772} }
France, J.L., Cain, M., Fisher, R.E., Lowry, D., Allen, G., O'Shea, S.J., Illingworth, S., Pyle, J., Warwick, N., Jones, B.T., Gallagher, M.W., Bower, K., Le Breton, M., Percival, C., Muller, J., Welpott, A., Bauguitte, S., George, C., Hayman, G.D., Manning, A.J., Myhre, C.L., Lanoiselle, M. and Nisbet, E.G. Measurements of δ13C in CH4 and using particle
dispersion modeling to characterize sources of Arctic methane within an
air mass
2016 JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Vol. 121(23), pp. 14257-14270 
article DOI  
Abstract: A stratified air mass enriched in methane (CH4) was sampled at similar
to 600m to similar to 2000m altitude, between the north coast of Norway
and Svalbard as part of the Methane in the Arctic: Measurements and
Modelling campaign on board the UK' s BAe-146-301 Atmospheric Research
Aircraft. The approach used here, which combines interpretation of
multiple tracers with transport modeling, enables better understanding
of the emission sources that contribute to the background mixing ratios
of CH4 in the Arctic. Importantly, it allows constraints to be placed on
the location and isotopic bulk signature of the emission source(s).
Measurements of delta C-13 in CH4 in whole air samples taken while
traversing the air mass identified that the source(s) had a strongly
depleted bulk delta C-13 CH4 isotopic signature of -70 (+/- 2.1)parts
per thousand. Combined Numerical Atmospheric-dispersion Modeling
Environment and inventory analysis indicates that the air mass was
recently in the planetary boundary layer over northwest Russia and the
Barents Sea, with the likely dominant source of methane being from
wetlands in that region.
BibTeX:
@article{WOS:000394520300028,
  author = {France, J. L. and Cain, M. and Fisher, R. E. and Lowry, D. and Allen, G.
and O'Shea, S. J. and Illingworth, S. and Pyle, J. and Warwick, N. and
Jones, B. T. and Gallagher, M. W. and Bower, K. and Le Breton, M. and
Percival, C. and Muller, J. and Welpott, A. and Bauguitte, S. and
George, C. and Hayman, G. D. and Manning, A. J. and Myhre, C. Lund and
Lanoiselle, M. and Nisbet, E. G.}, title = {Measurements of δ13C in CH4 and using particle
dispersion modeling to characterize sources of Arctic methane within an
air mass}, journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, year = {2016}, volume = {121}, number = {23}, pages = {14257-14270}, doi = {https://doi.org/10.1002/2016JD026006} }
Saunois, M., Bousquet, P., Poulter, B., Peregon, A., Ciais, P., Canadell, J.G., Dlugokencky, E.J., Etiope, G., Bastviken, D., Houweling, S., Janssens-Maenhout, G., Tubiello, F.N., Castaldi, S., Jackson, R.B., Alexe, M., Arora, V.K., Beerling, D.J., Bergamaschi, P., Blake, D.R., Brailsford, G., Brovkin, V., Bruhwiler, L., Crevoisier, C., Crill, P., Covey, K., Curry, C., Frankenberg, C., Gedney, N., Hoeglund-Isaksson, L., Ishizawa, M., Ito, A., Joos, F., Kim, H.-S., Kleinen, T., Krummel, P., Lamarque, J.-F., Langenfelds, R., Locatelli, R., Machida, T., Maksyutov, S., McDonald, K.C., Marshall, J., Melton, J.R., Morino, I., Naik, V., O'Doherty, S., Parmentier, F.-J.W., Patra, P.K., Peng, C., Peng, S., Peters, G.P., Pison, I., Prigent, C., Prinn, R., Ramonet, M., Riley, W.J., Saito, M., Santini, M., Schroeder, R., Simpson, I.J., Spahni, R., Steele, P., Takizawa, A., Thornton, B.F., Tian, H., Tohjima, Y., Viovy, N., Voulgarakis, A., van Weele, M., van der Werf, G.R., Weiss, R., Wiedinmyer, C., Wilton, D.J., Wiltshire, A., Worthy, D., Wunch, D., Xu, X., Yoshida, Y., Zhang, B., Zhang, Z. and Zhu, Q. The global methane budget 2000-2012 2016 EARTH SYSTEM SCIENCE DATA
Vol. 8(2), pp. 697-751 
article DOI  
Abstract: The global methane (CH4) budget is becoming an increasingly important
component for managing realistic pathways to mitigate climate change.
This relevance, due to a shorter atmospheric lifetime and a stronger
warming potential than carbon dioxide, is challenged by the still
unexplained changes of atmospheric CH4 over the past decade. Emissions
and concentrations of CH4 are continuing to increase, making CH4 the
second most important human-induced greenhouse gas after carbon dioxide.
Two major difficulties in reducing uncertainties come from the large
variety of diffusive CH4 sources that overlap geographically, and from
the destruction of CH4 by the very short-lived hydroxyl radical (OH). To
address these difficulties, we have established a consortium of
multi-disciplinary scientists under the umbrella of the Global Carbon
Project to synthesize and stimulate research on the methane cycle, and
producing regular (similar to biennial) updates of the global methane
budget. This consortium includes atmospheric physicists and chemists,
biogeochemists of surface and marine emissions, and socio-economists who
study anthropogenic emissions. Following Kirschke et al. (2013), we
propose here the first version of a living review paper that integrates
results of top-down studies (exploiting atmospheric observations within
an atmospheric inverse-modelling framework) and bottom-up models,
inventories and data-driven approaches (including process-based models
for estimating land surface emissions and atmospheric chemistry, and
inventories for anthropogenic emissions, data-driven extrapolations).
For the 2003-2012 decade, global methane emissions are estimated by
top-down inversions at 558 TgCH(4) yr(-1), range 540-568. About 60% of
global emissions are anthropogenic (range 50-65 %). Since 2010, the
bottom-up global emission inventories have been closer to methane
emissions in the most carbon-intensive Representative Concentrations
Pathway (RCP8.5) and higher than all other RCP scenarios. Bottom-up
approaches suggest larger global emissions (736 TgCH(4) yr(-1), range
596-884) mostly because of larger natural emissions from individual
sources such as inland waters, natural wetlands and geological sources.
Considering the atmospheric constraints on the top-down budget, it is
likely that some of the individual emissions reported by the bottom-up
approaches are overestimated, leading to too large global emissions.
Latitudinal data from top-down emissions indicate a predominance of
tropical emissions (similar to 64% of the global budget, <30 degrees N)
as compared to mid (similar to 32 %, 30-60 degrees N) and high northern
latitudes (similar to 4 %, 60-90 degrees N). Top-down inversions
consistently infer lower emissions in China (similar to 58 TgCH(4)
yr(-1), range 51-72, -14 %) and higher emissions in Africa (86 TgCH(4)
yr(-1), range 73-108, + 19 %) than bottom-up values used as prior
estimates. Overall, uncertainties for anthropogenic emissions appear
smaller than those from natural sources, and the uncertainties on source
categories appear larger for top-down inversions than for bottom-up
inventories and models.
The most important source of uncertainty on the methane budget is
attributable to emissions from wetland and other inland waters. We show
that the wetland extent could contribute 30-40% on the estimated range
for wetland emissions. Other priorities for improving the methane budget
include the following: (i) the development of process-based models for
inland-water emissions, (ii) the intensification of methane observations
at local scale (flux measurements) to constrain bottom-up land surface
models, and at regional scale (surface networks and satellites) to
constrain top-down inversions, (iii) improvements in the estimation of
atmospheric loss by OH, and (iv) improvements of the transport models
integrated in top-down inversions. The data presented here can be
downloaded from the Carbon Dioxide Information Analysis Center
(http://doi.org/10.3334/CDIAC/GLOBAL_METHANE_BUDGET_2016_V1.1) and
the Global Carbon Project.
BibTeX:
@article{WOS:000390145300001,
  author = {Saunois, Marielle and Bousquet, Philippe and Poulter, Ben and Peregon,
Anna and Ciais, Philippe and Canadell, Josep G. and Dlugokencky, Edward
J. and Etiope, Giuseppe and Bastviken, David and Houweling, Sander and
Janssens-Maenhout, Greet and Tubiello, Francesco N. and Castaldi, Simona
and Jackson, Robert B. and Alexe, Mihai and Arora, Vivek K. and
Beerling, David J. and Bergamaschi, Peter and Blake, Donald R. and
Brailsford, Gordon and Brovkin, Victor and Bruhwiler, Lori and
Crevoisier, Cyril and Crill, Patrick and Covey, Kristofer and Curry,
Charles and Frankenberg, Christian and Gedney, Nicola and
Hoeglund-Isaksson, Lena and Ishizawa, Misa and Ito, Akihiko and Joos,
Fortunat and Kim, Heon-Sook and Kleinen, Thomas and Krummel, Paul and
Lamarque, Jean-Francois and Langenfelds, Ray and Locatelli, Robin and
Machida, Toshinobu and Maksyutov, Shamil and McDonald, Kyle C. and
Marshall, Julia and Melton, Joe R. and Morino, Isamu and Naik, Vaishali
and O'Doherty, Simon and Parmentier, Frans-Jan W. and Patra, Prabir K.
and Peng, Changhui and Peng, Shushi and Peters, Glen P. and Pison,
Isabelle and Prigent, Catherine and Prinn, Ronald and Ramonet, Michel
and Riley, William J. and Saito, Makoto and Santini, Monia and
Schroeder, Ronny and Simpson, Isobel J. and Spahni, Renato and Steele,
Paul and Takizawa, Atsushi and Thornton, Brett F. and Tian, Hanqin and
Tohjima, Yasunori and Viovy, Nicolas and Voulgarakis, Apostolos and van
Weele, Michiel and van der Werf, Guido R. and Weiss, Ray and Wiedinmyer,
Christine and Wilton, David J. and Wiltshire, Andy and Worthy, Doug and
Wunch, Debra and Xu, Xiyan and Yoshida, Yukio and Zhang, Bowen and
Zhang, Zhen and Zhu, Qiuan}, title = {The global methane budget 2000-2012}, journal = {EARTH SYSTEM SCIENCE DATA}, year = {2016}, volume = {8}, number = {2}, pages = {697-751}, doi = {https://doi.org/10.5194/essd-8-697-2016} }
Jacob, D.J., Turner, A.J., Maasakkers, J.D., Sheng, J., Sun, K., Liu, X., Chance, K., Aben, I., McKeever, J. and Frankenberg, C. Satellite observations of atmospheric methane and their value for
quantifying methane emissions
2016 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 16(22), pp. 14371-14396 
article DOI  
Abstract: Methane is a greenhouse gas emitted by a range of natural and
anthropogenic sources. Atmospheric methane has been measured
continuously from space since 2003, and new instruments are planned for
launch in the near future that will greatly expand the capabilities of
space-based observations. We review the value of current, future, and
proposed satellite observations to better quantify and understand
methane emissions through inverse analyses, from the global scale down
to the scale of point sources and in combination with suborbital
(surface and aircraft) data. Current global observations from Greenhouse
Gases Observing Satellite (GOSAT) are of high quality but have sparse
spatial coverage. They can quantify methane emissions on a regional
scale (100-1000 km) through multiyear averaging. The Tropospheric
Monitoring Instrument (TROPOMI), to be launched in 2017, is expected to
quantify daily emissions on the regional scale and will also effectively
detect large point sources. A different observing strategy by GHGSat
(launched in June 2016) is to target limited viewing domains with very
fine pixel resolution in order to detect a wide range of methane point
sources. Geostationary observation of methane, still in the proposal
stage, will have the unique capability of mapping source regions with
high resolution, detecting transient ``super-emitter'' point sources
and resolving diurnal variation of emissions from sources such as
wetlands and manure. Exploiting these rapidly expanding satellite
measurement capabilities to quantify methane emissions requires a
parallel effort to construct high-quality spatially and sectorally
resolved emission inventories. Partnership between top-down inverse
analyses of atmospheric data and bottom-up construction of emission
inventories is crucial to better understanding methane emission
processes and subsequently informing climate policy.
BibTeX:
@article{WOS:000387980100003,
  author = {Jacob, Daniel J. and Turner, Alexander J. and Maasakkers, Joannes D. and
Sheng, Jianxiong and Sun, Kang and Liu, Xiong and Chance, Kelly and
Aben, Ilse and McKeever, Jason and Frankenberg, Christian}, title = {Satellite observations of atmospheric methane and their value for
quantifying methane emissions}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2016}, volume = {16}, number = {22}, pages = {14371-14396}, doi = {https://doi.org/10.5194/acp-16-14371-2016} }
Saito, M., Kim, H.-S., Ito, A., Yokota, T. and Maksyutov, S. Enhanced Methane Emissions during Amazonian Drought by Biomass Burning 2016 PLOS ONE
Vol. 11(11) 
article DOI  
Abstract: The Amazon is a significant source of atmospheric methane, but little is
known about the source response to increasing drought severity and
frequency. We investigated satellite observations of atmospheric
column-averaged methane for the 2010 drought and subsequent 2011 wet
year in the Amazon using an atmospheric inversion scheme. Our analysis
indicates an increase in atmospheric methane over the southern Amazon
region during the drought, representing an increase in annual emissions
relative to the wet year. We attribute the increase to emissions from
biomass burning driven by intense drought, combined with carbon monoxide
showing seasonal variations corresponding to methane variations. We show
that there is probably a strong correspondence between drought and
methane emissions in the Amazon.
BibTeX:
@article{WOS:000387909300032,
  author = {Saito, Makoto and Kim, Heon-Sook and Ito, Akihiko and Yokota, Tatsuya
and Maksyutov, Shamil}, title = {Enhanced Methane Emissions during Amazonian Drought by Biomass Burning}, journal = {PLOS ONE}, year = {2016}, volume = {11}, number = {11}, doi = {https://doi.org/10.1371/journal.pone.0166039} }
Tan, Z., Zhuang, Q., Henze, D.K., Frankenberg, C., Dlugokencky, E., Sweeney, C., Turner, A.J., Sasakawa, M. and Machida, T. Inverse modeling of pan-Arctic methane emissions at high spatial
resolution: what can we learn from assimilating satellite retrievals and
using different process-based wetland and lake biogeochemical models?
2016 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 16(19), pp. 12649-12666 
article DOI  
Abstract: Understanding methane emissions from the Arctic, a fast-warming carbon
reservoir, is important for projecting future changes in the global
methane cycle. Here we optimized methane emissions from north of 60
degrees N (pan-Arctic) regions using a nested-grid high-resolution
inverse model that assimilates both high-precision surface measurements
and column-average SCanning Imaging Absorption spectroMeter for
Atmospheric CHartogrphY (SCIAMACHY) satellite retrievals of methane mole
fraction. For the first time, methane emissions from lakes were
integrated into an atmospheric transport and inversion estimate,
together with prior wetland emissions estimated with six biogeochemical
models. In our estimates, in 2005, global methane emissions were in the
range of 496.4-511.5 Tg yr(-1), and pan-Arctic methane emissions were in
the range of 11.9-28.5 Tg yr(-1). Methane emissions from pan-Arctic
wetlands and lakes were 5.5-14.2 and 2.4-14.2 Tg yr(-1), respectively.
Methane emissions from Siberian wetlands and lakes are the largest and
also have the largest uncertainty. Our results indicate that the
uncertainty introduced by different wetland models could be much larger
than the uncertainty of each inversion. We also show that assimilating
satellite retrievals can reduce the un-certainty of the nested-grid
inversions. The significance of lake emissions cannot be identified
across the pan-Arctic by high-resolution inversions, but it is possible
to identify high lake emissions from some specific regions. In contrast
to global inversions, high-resolution nested-grid inversions perform
better in estimating near-surface methane concentrations.
BibTeX:
@article{WOS:000385403300001,
  author = {Tan, Zeli and Zhuang, Qianlai and Henze, Daven K. and Frankenberg,
Christian and Dlugokencky, Ed and Sweeney, Colm and Turner, Alexander J.
and Sasakawa, Motoki and Machida, Toshinobu}, title = {Inverse modeling of pan-Arctic methane emissions at high spatial
resolution: what can we learn from assimilating satellite retrievals and
using different process-based wetland and lake biogeochemical models?}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2016}, volume = {16}, number = {19}, pages = {12649-12666}, doi = {https://doi.org/10.5194/acp-16-12649-2016} }
Miller, S.M., Miller, C.E., Commane, R., Chang, R.Y.-W., Dinardo, S.J., Henderson, J.M., Karion, A., Lindaas, J., Melton, J.R., Miller, J.B., Sweeney, C., Wofsy, S.C. and Michalak, A.M. A multiyear estimate of methane fluxes in Alaska from CARVE atmospheric
observations
2016 GLOBAL BIOGEOCHEMICAL CYCLES
Vol. 30(10), pp. 1441-1453 
article DOI  
Abstract: Methane (CH4) fluxes from Alaska and other arctic regions may be
sensitive to thawing permafrost and future climate change, but estimates
of both current and future fluxes from the region are uncertain. This
study estimates CH4 fluxes across Alaska for 2012-2014 using aircraft
observations from the Carbon in Arctic Reservoirs Vulnerability
Experiment (CARVE) and a geostatistical inverse model (GIM). We find
that a simple flux model based on a daily soil temperature map and a
static map of wetland extent reproduces the atmospheric CH4 observations
at the statewide, multiyear scale more effectively than global-scale
process-based models. This result points to a simple and effective way
of representing CH4 fluxes across Alaska. It further suggests that
process-based models can improve their representation of key processes
and that more complex processes included in these models cannot be
evaluated given the information content of available atmospheric CH4
observations. In addition, we find that CH4 emissions from the North
Slope of Alaska account for 24% of the total statewide flux of 1.74 +/-
0.26 Tg CH4 (for May-October). Global-scale process models only
attribute an average of 3% of the total flux to this region. This
mismatch occurs for two reasons: process models likely underestimate
wetland extent in regions without visible surface water, and these
models prematurely shut down CH4 fluxes at soil temperatures near 0
degrees C. Lastly, we find that the seasonality of CH4 fluxes varied
during 2012-2014 but that total emissions did not differ significantly
among years, despite substantial differences in soil temperature and
precipitation.
BibTeX:
@article{WOS:000388458000004,
  author = {Miller, Scot M. and Miller, Charles E. and Commane, Roisin and Chang,
Rachel Y-W and Dinardo, Steven J. and Henderson, John M. and Karion,
Anna and Lindaas, Jakob and Melton, Joe R. and Miller, John B. and
Sweeney, Colm and Wofsy, Steven C. and Michalak, Anna M.}, title = {A multiyear estimate of methane fluxes in Alaska from CARVE atmospheric
observations}, journal = {GLOBAL BIOGEOCHEMICAL CYCLES}, year = {2016}, volume = {30}, number = {10}, pages = {1441-1453}, doi = {https://doi.org/10.1002/2016GB005419} }
Abdalla, M., Hastings, A., Truu, J., Espenberg, M., Mander, U. and Smith, P. Emissions of methane from northern peatlands: a review of management
impacts and implications for future management options
2016 ECOLOGY AND EVOLUTION
Vol. 6(19), pp. 7080-7102 
article DOI  
Abstract: Northern peatlands constitute a significant source of atmospheric
methane (CH4). However, management of undisturbed peatlands, as well as
the restoration of disturbed peatlands, will alter the exchange of CH4
with the atmosphere. The aim of this systematic review and meta-analysis
was to collate and analyze published studies to improve our
understanding of the factors that control CH4 emissions and the impacts
of management on the gas flux from northern (latitude 40 degrees to 70
degrees N) peatlands. The analysis includes a total of 87 studies
reporting measurements of CH4 emissions taken at 186 sites covering
different countries, peatland types, and management systems. Results
show that CH4 emissions from natural northern peatlands are highly
variable with a 95% CI of 7.6-15.7 g C m(-2) year(-1) for the mean and
3.3-6.3 g C m(-2) year(-1) for the median. The overall annual average
(mean +/- SD) is 12 +/- 21 g C m(-2) year(-1) with the highest emissions
from fen ecosystems. Methane emissions from natural peatlands are mainly
controlled by water table (WT) depth, plant community composition, and
soil pH. Although mean annual air temperature is not a good predictor of
CH4 emissions by itself, the interaction between temperature, plant
community cover, WT depth, and soil pH is important. According to
short-term forecasts of climate change, these complex interactions will
be the main determinant of CH4 emissions from northern peatlands.
Drainage significantly (p < .05) reduces CH4 emissions to the
atmosphere, on average by 84%. Restoration of drained peatlands by
rewetting or vegetation/rewetting increases CH4 emissions on average by
46% compared to the original premanagement CH4 fluxes. However, to
fully evaluate the net effect of management practice on the greenhouse
gas balance from high latitude peatlands, both net ecosystem exchange
(NEE) and carbon exports need to be considered.
BibTeX:
@article{WOS:000385626100029,
  author = {Abdalla, Mohamed and Hastings, Astley and Truu, Jaak and Espenberg, Mikk
and Mander, Ulo and Smith, Pete}, title = {Emissions of methane from northern peatlands: a review of management
impacts and implications for future management options}, journal = {ECOLOGY AND EVOLUTION}, year = {2016}, volume = {6}, number = {19}, pages = {7080-7102}, doi = {https://doi.org/10.1002/ece3.2469} }
Xu, X., Riley, W.J., Koven, C.D., Billesbach, D.P., Chang, R.Y.W., Commane, R., Euskirchen, E.S., Hartery, S., Harazono, Y., Iwata, H., McDonald, K.C., Miller, C.E., Oechel, W.C., Poulter, B., Raz-Yaseef, N., Sweeney, C., Torn, M., Wofsy, S.C., Zhang, Z. and Zona, D. A multi-scale comparison of modeled and observed seasonal methane
emissions in northern wetlands
2016 BIOGEOSCIENCES
Vol. 13(17), pp. 5043-5056 
article DOI  
Abstract: Wetlands are the largest global natural methane (CH4) source, and
emissions between 50 and 70 degrees N latitude contribute 10-30% to
this source. Predictive capability of land models for northern wetland
CH4 emissions is still low due to limited site measurements, strong
spatial and temporal variability in emissions, and complex hydrological
and biogeochemical dynamics. To explore this issue, we compare wetland
CH4 emission predictions from the Community Land Model 4.5 (CLM4.5-BGC)
with siteto regional-scale observations. A comparison of the CH4 fluxes
with eddy flux data highlighted needed changes to the model's estimate
of aerenchyma area, which we implemented and tested. The model
modification substantially reduced biases in CH4 emissions when compared
with CarbonTracker CH4 predictions. CLM4.5 CH4 emission predictions
agree well with growing season (May-September) CarbonTracker Alaskan
regional-level CH4 predictions and sitelevel observations. However,
CLM4.5 underestimated CH4 emissions in the cold season (October-April).
The monthly atmospheric CH4 mole fraction enhancements due to wetland
emissions are also assessed using the Weather Research and
Forecasting-Stochastic Time-Inverted Lagrangian Transport (WRF-STILT)
model coupled with daily emissions from CLM4.5 and compared with
aircraft CH4 mole fraction measurements from the Carbon in Arctic
Reservoirs Vulnerability Experiment (CARVE) campaign. Both the tower and
aircraft analyses confirm the underestimate of cold-season CH4 emissions
by CLM4.5. The greatest uncertainties in predicting the seasonal CH4
cycle are from the wetland extent, cold-season CH4 production and CH4
transport processes. We recommend more cold-season experimental studies
in high-latitude systems, which could improve the understanding and
parameterization of ecosystem structure and function during this period.
Predicted CH4 emissions remain uncertain, but we show here that
benchmarking against observations across spatial scales can inform model
structural and parameter improvements.
BibTeX:
@article{WOS:000383964200001,
  author = {Xu, Xiyan and Riley, William J. and Koven, Charles D. and Billesbach,
Dave P. and Chang, Rachel Y. -W. and Commane, Roisin and Euskirchen,
Eugenie S. and Hartery, Sean and Harazono, Yoshinobu and Iwata, Hiroki
and McDonald, Kyle C. and Miller, Charles E. and Oechel, Walter C. and
Poulter, Benjamin and Raz-Yaseef, Naama and Sweeney, Colm and Torn,
Margaret and Wofsy, Steven C. and Zhang, Zhen and Zona, Donatella}, title = {A multi-scale comparison of modeled and observed seasonal methane
emissions in northern wetlands}, journal = {BIOGEOSCIENCES}, year = {2016}, volume = {13}, number = {17}, pages = {5043-5056}, doi = {https://doi.org/10.5194/bg-13-5043-2016} }
Nisbet, E.G., Dlugokencky, E.J., Manning, M.R., Lowry, D., Fisher, R.E., France, J.L., Michel, S.E., Miller, J.B., White, J.W.C., Vaughn, B., Bousquet, P., Pyle, J.A., Warwick, N.J., Cain, M., Brownlow, R., Zazzeri, G., Lanoiselle, M., Manning, A.C., Gloor, E., Worthy, D.E.J., Brunke, E.-G., Labuschagne, C., Wolff, E.W. and Ganesan, A.L. Rising atmospheric methane: 2007-2014 growth and isotopic shift 2016 GLOBAL BIOGEOCHEMICAL CYCLES
Vol. 30(9), pp. 1356-1370 
article DOI  
Abstract: From 2007 to 2013, the globally averaged mole fraction of methane in the
atmosphere increased by 5.7 +/- 1.2 ppb yr(-1). Simultaneously, delta
C-13(CH4) (a measure of the C-13/C-12 isotope ratio in methane) has
shifted to significantly more negative values since 2007. Growth was
extreme in 2014, at 12.5 +/- 0.4 ppb, with a further shift to more
negative values being observed at most latitudes. The isotopic evidence
presented here suggests that the methane rise was dominated by
significant increases in biogenic methane emissions, particularly in the
tropics, for example, from expansion of tropical wetlands in years with
strongly positive rainfall anomalies or emissions from increased
agricultural sources such as ruminants and rice paddies. Changes in the
removal rate of methane by the OH radical have not been seen in other
tracers of atmospheric chemistry and do not appear to explain short-term
variations in methane. Fossil fuel emissions may also have grown, but
the sustained shift to more C-13-depleted values and its significant
interannual variability, and the tropical and Southern Hemisphere loci
of post-2007 growth, both indicate that fossil fuel emissions have not
been the dominant factor driving the increase. A major cause of
increased tropical wetland and tropical agricultural methane emissions,
the likely major contributors to growth, may be their responses to
meteorological change.
BibTeX:
@article{WOS:000388457700009,
  author = {Nisbet, E. G. and Dlugokencky, E. J. and Manning, M. R. and Lowry, D.
and Fisher, R. E. and France, J. L. and Michel, S. E. and Miller, J. B.
and White, J. W. C. and Vaughn, B. and Bousquet, P. and Pyle, J. A. and
Warwick, N. J. and Cain, M. and Brownlow, R. and Zazzeri, G. and
Lanoiselle, M. and Manning, A. C. and Gloor, E. and Worthy, D. E. J. and
Brunke, E-G. and Labuschagne, C. and Wolff, E. W. and Ganesan, A. L.}, title = {Rising atmospheric methane: 2007-2014 growth and isotopic shift}, journal = {GLOBAL BIOGEOCHEMICAL CYCLES}, year = {2016}, volume = {30}, number = {9}, pages = {1356-1370}, doi = {https://doi.org/10.1002/2016GB005406} }
Rockmann, T., Eyer, S., van der Veen, C., Popa, M.E., Tuzson, B., Monteil, G., Houweling, S., Harris, E., Brunner, D., Fischer, H., Zazzeri, G., Lowry, D., Nisbet, E.G., Brand, W.A., Necki, J.M., Emmenegger, L. and Mohn, J. In situ observations of the isotopic composition of methane at the
Cabauw tall tower site
2016 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 16(16), pp. 10469-10487 
article DOI  
Abstract: High-precision analyses of the isotopic composition of methane in
ambient air can potentially be used to discriminate between different
source categories. Due to the complexity of isotope ratio measurements,
such analyses have generally been performed in the laboratory on air
samples collected in the field. This poses a limitation on the temporal
resolution at which the isotopic composition can be monitored with
reasonable logistical effort. Here we present the performance of a dual
isotope ratio mass spectrometric system (IRMS) and a quantum cascade
laser absorption spectroscopy (QCLAS)-based technique for in situ
analysis of the isotopic composition of methane under field conditions.
Both systems were deployed at the Cabauw Experimental Site for
Atmospheric Research (CESAR) in the Netherlands and performed in situ,
high-frequency (approx. hourly) measurements for a period of more than 5
months. The IRMS and QCLAS instruments were in excellent agreement with
a slight systematic offset of (+0.25 +/- 0.04)parts per thousand for
delta C-13 and (-4.3 +/- 0.4)parts per thousand for delta D. This was
corrected for, yielding a combined dataset with more than 2500
measurements of both delta C-13 and delta D. The high-precision and
high-temporal-resolution dataset not only reveals the overwhelming
contribution of isotopically depleted agricultural CH4 emissions from
ruminants at the Cabauw site but also allows the identification of
specific events with elevated contributions from more enriched sources
such as natural gas and landfills. The final dataset was compared to
model calculations using the global model TM5 and the mesoscale model
FLEXPART-COSMO. The results of both models agree better with the
measurements when the TNO-MACC emission inventory is used in the models
than when the EDGAR inventory is used. This suggests that
high-resolution isotope measurements have the potential to further
constrain the methane budget when they are performed at multiple sites
that are representative for the entire European domain.
BibTeX:
@article{WOS:000383742700003,
  author = {Rockmann, Thomas and Eyer, Simon and van der Veen, Carina and Popa,
Maria E. and Tuzson, Bela and Monteil, Guillaume and Houweling, Sander
and Harris, Eliza and Brunner, Dominik and Fischer, Hubertus and
Zazzeri, Giulia and Lowry, David and Nisbet, Euan G. and Brand, Willi A.
and Necki, Jaroslav M. and Emmenegger, Lukas and Mohn, Joachim}, title = {In situ observations of the isotopic composition of methane at the
Cabauw tall tower site}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2016}, volume = {16}, number = {16}, pages = {10469-10487}, doi = {https://doi.org/10.5194/acp-16-10469-2016} }
Xiong, X., Han, Y., Liu, Q. and Weng, F. Comparison of Atmospheric Methane Retrievals From AIRS and IASI 2016 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE
SENSING
Vol. 9(7, SI), pp. 3297-3303 
article DOI  
Abstract: Atmospheric methane (CH4) is a standard product of the atmospheric
infrared sounder (AIRS) aboard NASA's Aqua satellite, generated at the
NASA Goddard Earth Sciences Data and Information Services Center
(NASA/GES/DISC), and a product of the infrared atmospheric sounding
interferometer (IASI) aboard METOP-A,-B, generated at National Oceanic
and Atmospheric Administration's Comprehensive Large Array-data
Stewardship System. In order to understand the capability of these two
sensors in observing the spatial and temporal distribution of CH4, this
paper compares the CH4 products from AIRS and IASI with aircraft
measurements, as well as the corresponding time series in tropics and
high northern latitude regions. It is found that the mean degree of
freedom from AIRS is smaller than IASI by -0.049 +/- 0.152, and in their
peak sensitive altitude between 350 and 650 hPa their difference (AIRS -
IASI) is about 2.8 +/- 17.2 ppb. Both AIRS and IASI can capture the
latitudinal gradient, but there is a large scattering in the high
northern latitude regions. They agree well in observing the summer
enhancement of CH4 during the Monsoon season over South Asia, and the
seasonal cycles over Siberia (except for a relatively larger difference
in the cold season). These results highlight that AIRS and IASI can
provide valuable information to capture the spatiotemporal variation of
CH4 in the mid-upper troposphere in most periods and regions, but it is
needed to further improve the data quality to make a consistent product
using both sensors.
BibTeX:
@article{WOS:000384905500040,
  author = {Xiong, Xiaozhen and Han, Yong and Liu, Quanhua and Weng, Fuzhong},
  title = {Comparison of Atmospheric Methane Retrievals From AIRS and IASI},
  journal = {IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE
SENSING}, year = {2016}, volume = {9}, number = {7, SI}, pages = {3297-3303}, doi = {https://doi.org/10.1109/JSTARS.2016.2588279} }
Sweeney, C., Dlugokencky, E., Miller, C.E., Wofsy, S., Karion, A., Dinardo, S., Chang, R.Y.W., Miller, J.B., Bruhwiler, L., Crotwell, A.M., Newberger, T., McKain, K., Stone, R.S., Wolter, S.E., Lang, P.E. and Tans, P. No significant increase in long-term CH4 emissions on North
Slope of Alaska despite significant increase in air temperature
2016 GEOPHYSICAL RESEARCH LETTERS
Vol. 43(12), pp. 6604-6611 
article DOI  
Abstract: Continuous measurements of atmospheric methane (CH4) mole fractions
measured by NOAA's Global Greenhouse Gas Reference Network in Barrow, AK
(BRW), show strong enhancements above background values when winds come
from the land sector from July to December from 1986 to 2015, indicating
that emissions from arctic tundra continue through autumn and into early
winter. Twenty-nine years of measurements show little change in seasonal
mean land sector CH4 enhancements, despite an increase in annual mean
temperatures of 1.2 +/- 0.8 degrees C/decade (2s). The record does
reveal small increases in CH4 enhancements in November and December
after 2010 due to increased late-season emissions. The lack of
significant long-term trends suggests that more complex biogeochemical
processes are counteracting the observed short-term (monthly)
temperature sensitivity of 5.0 +/- 3.6 ppb CH4/degrees C. Our results
suggest that even the observed short-term temperature sensitivity from
the Arctic will have little impact on the global atmospheric CH4 budget
in the long term if future trajectories evolve with the same temperature
sensitivity.
BibTeX:
@article{WOS:000380910100083,
  author = {Sweeney, Colm and Dlugokencky, Edward and Miller, Charles E. and Wofsy,
Steven and Karion, Anna and Dinardo, Steve and Chang, Rachel Y. -W. and
Miller, John B. and Bruhwiler, Lori and Crotwell, Andrew M. and
Newberger, Tim and McKain, Kathryn and Stone, Robert S. and Wolter,
Sonja E. and Lang, Patricia E. and Tans, Pieter}, title = {No significant increase in long-term CH4 emissions on North
Slope of Alaska despite significant increase in air temperature}, journal = {GEOPHYSICAL RESEARCH LETTERS}, year = {2016}, volume = {43}, number = {12}, pages = {6604-6611}, doi = {https://doi.org/10.1002/2016GL069292} }
Uttal, T., Starkweather, S., Drummond, J.R., Vihma, T., Makshtas, A.P., Darby, L.S., Burkhart, J.F., Cox, C.J., Schmeisser, L.N., Haiden, T., Maturilli, M., Shupe, M.D., De Boer, G., Saha, A., Grachev, A.A., Crepinsek, S.M., Bruhwiler, L., Goodison, B., McArthur, B., Walden, V.P., Dlugokencky, E.J., Persson, P.O.G., Lesins, G., Laurila, T., Ogren, J.A., Stone, R., Long, C.N., Sharma, S., Massling, A., Turner, D.D., Stanitski, D.M., Asmi, E., Aurela, M., Skov, H., Eleftheriadis, K., Virkkula, A., Platt, A., Forland, E.J., Iijima, Y., Nielsen, I.E., Bergin, M.H., Candlish, L., Zimov, N.S., Zimov, S.A., O'Neill, N.T., Fogal, P.F., Kivi, R., Konopleva-Akish, E.A., Verlinde, J., Kustov, V.Y., Vasel, B., Ivakhov, V.M., Viisanen, Y. and Intrieri, J.M. International Arctic Systems for Observing the Atmosphere: An
International Polar Year Legacy Consortium
2016 BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY
Vol. 97(6), pp. 1033-1056 
article DOI  
Abstract: International Arctic Systems for Observing the Atmosphere (IASOA)
activities and partnerships were initiated as a part of the 2007-09
International Polar Year (IPY) and are expected to continue for many
decades as a legacy program. The IASOA focus is on coordinating
intensive measurements of the Arctic atmosphere collected in the United
States, Canada, Russia, Norway, Finland, and Greenland to create
synthesis science that leads to an understanding of why and not just how
the Arctic atmosphere is evolving. The IASOA premise is that there are
limitations with Arctic modeling and satellite observations that can
only be addressed with boots-on-the-ground, in situ observations and
that the potential of combining individual station and network
measurements into an integrated observing system is tremendous. The
IASOA vision is that by further integrating with other network observing
programs focusing on hydrology, glaciology, oceanography, terrestrial,
and biological systems it will be possible to understand the mechanisms
of the entire Arctic system, perhaps well enough for humans to mitigate
undesirable variations and adapt to inevitable change.
BibTeX:
@article{WOS:000380345200013,
  author = {Uttal, Taneil and Starkweather, Sandra and Drummond, James R. and Vihma,
Timo and Makshtas, Alexander P. and Darby, Lisa S. and Burkhart, John F.
and Cox, Christopher J. and Schmeisser, Lauren N. and Haiden, Thomas and
Maturilli, Marion and Shupe, Matthew D. and De Boer, Gijs and Saha,
Auromeet and Grachev, Andrey A. and Crepinsek, Sara M. and Bruhwiler,
Lori and Goodison, Barry and McArthur, Bruce and Walden, Von P. and
Dlugokencky, Edward J. and Persson, P. Ola G. and Lesins, Glen and
Laurila, Tuomas and Ogren, John A. and Stone, Robert and Long, Charles
N. and Sharma, Sangeeta and Massling, Andreas and Turner, David D. and
Stanitski, Diane M. and Asmi, Eija and Aurela, Mika and Skov, Henrik and
Eleftheriadis, Konstantinos and Virkkula, Aki and Platt, Andrew and
Forland, Eirik J. and Iijima, Yoshihiro and Nielsen, Ingeborg E. and
Bergin, Michael H. and Candlish, Lauren and Zimov, Nikita S. and Zimov,
Sergey A. and O'Neill, Norman T. and Fogal, Pierre F. and Kivi, Rigel
and Konopleva-Akish, Elena A. and Verlinde, Johannes and Kustov, Vasily
Y. and Vasel, Brian and Ivakhov, Viktor M. and Viisanen, Yrjoe and
Intrieri, Janet M.}, title = {International Arctic Systems for Observing the Atmosphere: An
International Polar Year Legacy Consortium}, journal = {BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, year = {2016}, volume = {97}, number = {6}, pages = {1033-1056}, doi = {https://doi.org/10.1175/BAMS-D-14-00145.1} }
Liu, M., Lei, L., Liu, D. and Zeng, Z.-C. Geostatistical Analysis of CH4 Columns over Monsoon Asia
Using Five Years of GOSAT Observations
2016 REMOTE SENSING
Vol. 8(5) 
article DOI  
Abstract: The aim of this study is to evaluate the Greenhouse gases Observation
SATellite (GOSAT) column-averaged CH4 dry air mole fraction (XCH4) data
by using geostatistical analysis and conducting comparisons with model
simulations and surface emissions. Firstly, we propose the use of a
data-driven mapping approach based on spatio-temporal geostatistics to
generate a regular and gridded mapping dataset of XCH4 over Monsoon Asia
using five years of XCH4 retrievals by GOSAT from June 2009 to May 2014.
The prediction accuracy of the mapping approach is assessed by using
cross-validation, which results in a significantly high correlation of
0.91 and a small mean absolute prediction error of 8.77 ppb between the
observed dataset and the prediction dataset. Secondly, with the mapping
data, we investigate the spatial and temporal variations of XCH4 over
Monsoon Asia and compare the results with previous studies on ground and
other satellite observations. Thirdly, we compare the mapping XCH4 with
model simulations from CarbonTracker-CH4 and find their spatial patterns
very consistent, but GOSAT observations are more able to capture the
local variability of XCH4. Finally, by correlating the mapping data with
surface emission inventory, we find the geographical distribution of
high CH4 values correspond well with strong emissions as indicated in
the inventory map. Over the five-year period, the two datasets show a
significant high correlation coefficient (0.80), indicating the dominant
role of surface emissions in determining the distribution of XCH4
concentration in this region and suggesting a promising statistical way
of constraining surface CH4 sources and sinks, which is simple and easy
to implement using satellite observations over a long term period.
BibTeX:
@article{WOS:000378406400005,
  author = {Liu, Min and Lei, Liping and Liu, Da and Zeng, Zhao-Cheng},
  title = {Geostatistical Analysis of CH4 Columns over Monsoon Asia
Using Five Years of GOSAT Observations}, journal = {REMOTE SENSING}, year = {2016}, volume = {8}, number = {5}, doi = {https://doi.org/10.3390/rs8050361} }
Turner, A.J., Jacob, D.J., Benmergui, J., Wofsy, S.C., Maasakkers, J.D., Butz, A., Hasekamp, O. and Biraud, S.C. A large increase in US methane emissions over the past decade inferred
from satellite data and surface observations
2016 GEOPHYSICAL RESEARCH LETTERS
Vol. 43(5), pp. 2218-2224 
article DOI  
Abstract: The global burden of atmospheric methane has been increasing over the
past decade, but the causes are not well understood. National inventory
estimates from the U.S. Environmental Protection Agency indicate no
significant trend in U.S. anthropogenic methane emissions from 2002 to
present. Here we use satellite retrievals and surface observations of
atmospheric methane to suggest that U.S. methane emissions have
increased by more than 30% over the 2002-2014 period. The trend is
largest in the central part of the country, but we cannot readily
attribute it to any specific source type. This large increase in U.S.
methane emissions could account for 30-60% of the global growth of
atmospheric methane seen in the past decade.
BibTeX:
@article{WOS:000373109800053,
  author = {Turner, A. J. and Jacob, D. J. and Benmergui, J. and Wofsy, S. C. and
Maasakkers, J. D. and Butz, A. and Hasekamp, O. and Biraud, S. C.}, title = {A large increase in US methane emissions over the past decade inferred
from satellite data and surface observations}, journal = {GEOPHYSICAL RESEARCH LETTERS}, year = {2016}, volume = {43}, number = {5}, pages = {2218-2224}, doi = {https://doi.org/10.1002/2016GL067987} }
Tian, H., Lu, C., Ciais, P., Michalak, A.M., Canadell, J.G., Saikawa, E., Huntzinger, D.N., Gurney, K.R., Sitch, S., Zhang, B., Yang, J., Bousquet, P., Bruhwiler, L., Chen, G., Dlugokencky, E., Friedlingstein, P., Melillo, J., Pan, S., Poulter, B., Prinn, R., Saunois, M., Schwalm, C.R. and Wofsy, S.C. The terrestrial biosphere as a net source of greenhouse gases to the
atmosphere
2016 NATURE
Vol. 531(7593), pp. 225+ 
article DOI  
Abstract: The terrestrial biosphere can release or absorb the greenhouse gases,
carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and
therefore has an important role in regulating atmospheric composition
and climate1. Anthropogenic activities such as land-use change,
agriculture and waste management have altered terrestrial biogenic
greenhouse gas fluxes, and the resulting increases in methane and
nitrous oxide emissions in particular can contribute to climate
change(2,3). The terrestrial biogenic fluxes of individual greenhouse
gases have been studied extensively(4-6), but the net biogenic
greenhouse gas balance resulting from anthropogenic activities and its
effect on the climate system remains uncertain. Here we use bottom-up
(inventory, statistical extrapolation of local flux measurements, and
process-based modelling) and top-down (atmospheric inversions)
approaches to quantify the global net biogenic greenhouse gas balance
between 1981 and 2010 resulting from anthropogenic activities and its
effect on the climate system. We find that the cumulative warming
capacity of concurrent biogenic methane and nitrous oxide emissions is a
factor of about two larger than the cooling effect resulting from the
global land carbon dioxide uptake from 2001 to 2010. This results in a
net positive cumulative impact of the three greenhouse gases on the
planetary energy budget, with a best estimate (in petagrams of CO2
equivalent per year) of 3.9 +/- 3.8 (top down) and 5.4 +/- 4.8 (bottom
up) based on the GWP100 metric (global warming potential on a 100-year
time horizon). Our findings suggest that a reduction in agricultural
methane and nitrous oxide emissions, particularly in Southern Asia, may
help mitigate climate change.
BibTeX:
@article{WOS:000371665100039,
  author = {Tian, Hanqin and Lu, Chaoqun and Ciais, Philippe and Michalak, Anna M.
and Canadell, Josep G. and Saikawa, Eri and Huntzinger, Deborah N. and
Gurney, Kevin R. and Sitch, Stephen and Zhang, Bowen and Yang, Jia and
Bousquet, Philippe and Bruhwiler, Lori and Chen, Guangsheng and
Dlugokencky, Edward and Friedlingstein, Pierre and Melillo, Jerry and
Pan, Shufen and Poulter, Benjamin and Prinn, Ronald and Saunois,
Marielle and Schwalm, Christopher R. and Wofsy, Steven C.}, title = {The terrestrial biosphere as a net source of greenhouse gases to the
atmosphere}, journal = {NATURE}, year = {2016}, volume = {531}, number = {7593}, pages = {225+}, doi = {https://doi.org/10.1038/nature16946} }
Wik, M., Varner, R.K., Anthony, K.W., MacIntyre, S. and Bastviken, D. Climate-sensitive northern lakes and ponds are critical components of
methane release
2016 NATURE GEOSCIENCE
Vol. 9(2), pp. 99+ 
article DOI  
Abstract: Lakes and ponds represent one of the largest natural sources of the
greenhouse gas methane. By surface area, almost half of these waters are
located in the boreal region and northwards. A synthesis of measurements
of methane emissions from 733 lakes and ponds north of similar to 50
degrees N, combined with new inventories of inland waters, reveals that
emissions from these high latitudes amount to around 16.5 Tg CH4 yr(-1)
(12.4 Tg CH4-C yr(-1)). This estimate - from lakes and ponds alone - is
equivalent to roughly two-thirds of the inverse model calculation of all
natural methane sources in the region. Thermokarst water bodies have
received attention for their high emission rates, but we find that
post-glacial lakes are a larger regional source due to their larger
areal extent. Water body depth, sediment type and ecoclimatic region are
also important in explaining variation in methane fluxes. Depending on
whether warming and permafrost thaw cause expansion or contraction of
lake and pond areal coverage, we estimate that annual water body
emissions will increase by 20-54% before the end of the century if
ice-free seasons are extended by 20 days. We conclude that lakes and
ponds are a dominant methane source at high northern latitudes.
BibTeX:
@article{WOS:000369324600010,
  author = {Wik, Martin and Varner, Ruth K. and Anthony, Katey Walter and MacIntyre,
Sally and Bastviken, David}, title = {Climate-sensitive northern lakes and ponds are critical components of
methane release}, journal = {NATURE GEOSCIENCE}, year = {2016}, volume = {9}, number = {2}, pages = {99+}, doi = {https://doi.org/10.1038/NGEO2578} }
Zona, D., Gioli, B., Commane, R., Lindaas, J., Wofsy, S.C., Miller, C.E., Dinardo, S.J., Dengel, S., Sweeney, C., Karion, A., Chang, R.Y.W., Henderson, J.M., Murphy, P.C., Goodrich, J.P., Moreaux, V., Liljedahl, A., Watts, J.D., Kimball, J.S., Lipson, D.A. and Oechel, W.C. Cold season emissions dominate the Arctic tundra methane budget 2016 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF
AMERICA
Vol. 113(1), pp. 40-45 
article DOI  
Abstract: Arctic terrestrial ecosystems are major global sources of methane (CH4);
hence, it is important to understand the seasonal and climatic controls
on CH4 emissions from these systems. Here, we report year-round CH4
emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes
derived from aircraft data. We find that emissions during the cold
season (September to May) account for >= 50% of the annual CH4 flux,
with the highest emissions from noninundated upland tundra. A major
fraction of cold season emissions occur during the ``zero curtain''
period, when subsurface soil temperatures are poised near 0 degrees C.
The zero curtain may persist longer than the growing season, and CH4
emissions are enhanced when the duration is extended by a deep thawed
layer as can occur with thick snow cover. Regional scale fluxes of CH4
derived from aircraft data demonstrate the large spatial extent of late
season CH4 emissions. Scaled to the circumpolar Arctic, cold season
fluxes from tundra total 12 +/- 5 (95% confidence interval) Tg CH4
y(-1), similar to 25% of global emissions from extratropical wetlands,
or similar to 6% of total global wetland methane emissions. The
dominance of late-season emissions, sensitivity to soil environmental
conditions, and importance of dry tundra are not currently simulated in
most global climate models. Because Arctic warming disproportionally
impacts the cold season, our results suggest that higher cold-season CH4
emissions will result from observed and predicted increases in snow
thickness, active layer depth, and soil temperature, representing
important positive feedbacks on climate warming.
BibTeX:
@article{WOS:000367520400029,
  author = {Zona, Donatella and Gioli, Beniamino and Commane, Roisin and Lindaas,
Jakob and Wofsy, Steven C. and Miller, Charles E. and Dinardo, Steven J.
and Dengel, Sigrid and Sweeney, Colm and Karion, Anna and Chang, Rachel
Y. -W. and Henderson, John M. and Murphy, Patrick C. and Goodrich,
Jordan P. and Moreaux, Virginie and Liljedahl, Anna and Watts, Jennifer
D. and Kimball, John S. and Lipson, David A. and Oechel, Walter C.}, title = {Cold season emissions dominate the Arctic tundra methane budget}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF
AMERICA}, year = {2016}, volume = {113}, number = {1}, pages = {40-45}, doi = {https://doi.org/10.1073/pnas.1516017113} }
Miller, S.M., Commane, R., Melton, J.R., Andrews, A.E., Benmergui, J., Dlugokencky, E.J., Janssens-Maenhout, G., Michalak, A.M., Sweeney, C. and Worthy, D.E.J. Evaluation of wetland methane emissions across North America using
atmospheric data and inverse modeling
2016 BIOGEOSCIENCES
Vol. 13(4), pp. 1329-1339 
article DOI  
Abstract: Existing estimates of methane (CH4) fluxes from North American wetlands
vary widely in both magnitude and distribution. In light of these
differences, this study uses atmospheric CH4 observations from the US
and Canada to analyze seven different bottom-up, wetland CH4 estimates
reported in a recent model comparison project. We first use synthetic
data to explore whether wetland CH4 fluxes are detectable at atmospheric
observation sites. We find that the observation network can detect
aggregate wetland fluxes from both eastern and western Canada but
generally not from the US. Based upon these results, we then use real
data and inverse modeling results to analyze the magnitude, seasonality,
and spatial distribution of each model estimate. The magnitude of
Canadian fluxes in many models is larger than indicated by atmospheric
observations. Many models predict a seasonality that is narrower than
implied by inverse modeling results, possibly indicating an
oversensitivity to air or soil temperatures. The LPJ-Bern and SDGVM
models have a geographic distribution that is most consistent with
atmospheric observations, depending upon the region and season. These
models utilize land cover maps or dynamic modeling to estimate wetland
coverage while most other models rely primarily on remote sensing
inundation data.
BibTeX:
@article{WOS:000372082200030,
  author = {Miller, Scot M. and Commane, Roisin and Melton, Joe R. and Andrews,
Arlyn E. and Benmergui, Joshua and Dlugokencky, Edward J. and
Janssens-Maenhout, Greet and Michalak, Anna M. and Sweeney, Colm and
Worthy, Doug E. J.}, title = {Evaluation of wetland methane emissions across North America using
atmospheric data and inverse modeling}, journal = {BIOGEOSCIENCES}, year = {2016}, volume = {13}, number = {4}, pages = {1329-1339}, doi = {https://doi.org/10.5194/bg-13-1329-2016} }
Dalsoren, S.B., Myhre, C.L., Myhre, G., Gomez-Pelaez, A.J., Sovde, O.A., Isaksen, I.S.A., Weiss, R.F. and Harth, C.M. Atmospheric methane evolution the last 40 years 2016 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 16(5), pp. 3099-3126 
article DOI  
Abstract: Observations at surface sites show an increase in global mean surface
methane (CH4) of about 180 parts per billion (ppb) (above 10 %) over
the period 1984-2012. Over this period there are large fluctuations in
the annual growth rate. In this work, we investigate the atmospheric CH4
evolution over the period 1970-2012 with the Oslo CTM3 global chemical
transport model (CTM) in a bottom-up approach. We thoroughly assess data
from surface measurement sites in international networks and select a
subset suited for comparisons with the output from the CTM. We compare
model results and observations to understand causes for both long-term
trends and short-term variations. Employing Oslo CTM3 we are able to
reproduce the seasonal and year-to-year variations and shifts between
years with consecutive growth and stagnation, both at global and
regional scales. The overall CH4 trend over the period is reproduced,
but for some periods the model fails to reproduce the strength of the
growth. The model overestimates the observed growth after 2006 in all
regions. This seems to be explained by an overly strong increase in
anthropogenic emissions in Asia, having global impact. Our findings
confirm other studies questioning the timing or strength of the emission
changes in Asia in the EDGAR v4.2 emission inventory over recent
decades. The evolution of CH4 is not only controlled by changes in
sources, but also by changes in the chemical loss in the atmosphere and
soil uptake. The atmospheric CH4 lifetime is an indicator of the CH4
loss. In our simulations, the atmospheric CH4 lifetime decreases by more
than 8 % from 1970 to 2012, a significant reduction of the residence
time of this important greenhouse gas. Changes in CO and NOx emissions,
specific humidity, and ozone column drive most of this, and we provide
simple prognostic equations for the relations between those and the CH4
lifetime. The reduced lifetime results in substantial growth in the
chemical CH4 loss (relative to its burden) and dampens the CH4 growth.
BibTeX:
@article{WOS:000374702000022,
  author = {Dalsoren, Stig B. and Myhre, Cathrine L. and Myhre, Gunnar and
Gomez-Pelaez, Angel J. and Sovde, Ole A. and Isaksen, Ivar S. A. and
Weiss, Ray F. and Harth, Christina M.}, title = {Atmospheric methane evolution the last 40 years}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2016}, volume = {16}, number = {5}, pages = {3099-3126}, doi = {https://doi.org/10.5194/acp-16-3099-2016} }
Hausmann, P., Sussmann, R. and Smale, D. Contribution of oil and natural gas production to renewed increase in
atmospheric methane (2007-2014): top-down estimate from ethane and
methane column observations
2016 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 16(5), pp. 3227-3244 
article DOI  
Abstract: Harmonized time series of column-averaged mole fractions of atmospheric
methane and ethane over the period 1999-2014 are derived from solar
Fourier transform infrared (FTIR) measurements at the Zugspitze summit
(47A degrees aEuro-N, 11A degrees aEuro-E; 2964 m a.s.l.) and at Lauder
(45A degrees aEuro-S, 170A degrees aEuro-E; 370 m a.s.l.). Long-term
trend analysis reveals a consistent renewed methane increase since 2007
of 6.2 [5.6, 6.9] ppb yr(-1) (parts-per-billion per year) at the
Zugspitze and 6.0 [5.3, 6.7] ppb yr(-1) at Lauder (95 % confidence
intervals). Several recent studies provide pieces of evidence that the
renewed methane increase is most likely driven by two main factors: (i)
increased methane emissions from tropical wetlands, followed by (ii)
increased thermogenic methane emissions due to growing oil and natural
gas production. Here, we quantify the magnitude of the second class of
sources, using long-term measurements of atmospheric ethane as a tracer
for thermogenic methane emissions. In 2007, after years of weak decline,
the Zugspitze ethane time series shows the sudden onset of a significant
positive trend (2.3 [1.8, 2.8]x -10(-2) ppb yr(-1) for 2007-2014),
while a negative trend persists at Lauder after 2007 (-0.4 [-0.6,
-0.1]x -10(-2) ppb yr(-1)). Zugspitze methane and ethane time series are
significantly correlated for the period 2007-2014 and can be assigned to
thermogenic methane emissions with an ethane-to-methane ratio (EMR) of
12-19 %. We present optimized emission scenarios for 2007-2014 derived
from an atmospheric two-box model. From our trend observations we infer
a total ethane emission increase over the period 2007-2014 from oil and
natural gas sources of 1-11 Tg yr(-1) along with an overall methane
emission increase of 24-45 Tg yr(-1). Based on these results, the oil
and natural gas emission contribution (C) to the renewed methane
increase is deduced using three different emission scenarios with
dedicated EMR ranges. Reference scenario 1 assumes an oil and gas
emission combination with EMR= -7.0-16.2 %, which results in a minimum
contribution C > -39 % (given as lower bound of 95 % confidence
interval). Beside this most plausible scenario 1, we consider two less
realistic limiting cases of pure oil-related emissions (scenario 2 with
EMR= -16.2-31.4 %) and pure natural gas sources (scenario 3 with EMR=
-4.4-7.0- %), which result in C > -18 % and C > -73 %, respectively.
Our results suggest that long-term observations of column-averaged
ethane provide a valuable constraint on the source attribution of
methane emission changes and provide basic knowledge for developing
effective climate change mitigation strategies.
BibTeX:
@article{WOS:000374702000029,
  author = {Hausmann, Petra and Sussmann, Ralf and Smale, Dan},
  title = {Contribution of oil and natural gas production to renewed increase in
atmospheric methane (2007-2014): top-down estimate from ethane and
methane column observations}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2016}, volume = {16}, number = {5}, pages = {3227-3244}, doi = {https://doi.org/10.5194/acp-16-3227-2016} }
Pandey, S., Houweling, S., Krol, M., Aben, I., Chevallier, F., Dlugokencky, E.J., Gatti, L.V., Gloor, E., Miller, J.B., Detmers, R., Machida, T. and Rockmann, T. Inverse modeling of GOSAT-retrieved ratios of total column
CH4 and CO2 for 2009 and 2010
2016 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 16(8), pp. 5043-5062 
article DOI  
Abstract: This study investigates the constraint provided by greenhouse gas
measurements from space on surface fluxes. Imperfect knowledge of the
light path through the atmosphere, arising from scattering by clouds and
aerosols, can create biases in column measurements retrieved from space.
To minimize the impact of such biases, ratios of total column retrieved
CH4 and CO2 (X-ratio) have been used. We apply the ratio inversion
method described in Pandey et al. (2015) to retrievals from the
Greenhouse Gases Observing SATellite (GOSAT). The ratio inversion method
uses the measured X-ratio as a weak constraint on CO2 fluxes. In
contrast, the more common approach of inverting proxy CH4 retrievals
(Frankenberg et al., 2005) prescribes atmospheric CO2 fields and
optimizes only CH4 fluxes.
The TM5-4DVAR (Tracer Transport Model version 5-variational data
assimilation system) inverse modeling system is used to simultaneously
optimize the fluxes of CH4 and CO2 for 2009 and 2010. The results are
compared to proxy inversions using model-derived CO2 mixing ratios
(XCO2model) from CarbonTracker and the Monitoring Atmospheric
Composition and Climate (MACC) Reanalysis CO2 product. The performance
of the inverse models is evaluated using measurements from three
aircraft measurement projects.
X-ratio and XCO2model are compared with TCCON retrievals to quantify the
relative importance of errors in these components of the proxy XCH4
retrieval (XCH4proxy). We find that the retrieval errors in X-ratio
(meanaEuro- = aEuro-0.61aEuro-%) are generally larger than the errors
in XCO2model (meanaEuro- = aEuro-0.24 and 0.01aEuro-% for CarbonTracker
and MACC, respectively). On the annual timescale, the CH4 fluxes from
the different satellite inversions are generally in agreement with each
other, suggesting that errors in XCO2model do not limit the overall
accuracy of the CH4 flux estimates. On the seasonal timescale, however,
larger differences are found due to uncertainties in XCO2model,
particularly over Australia and in the tropics. The ratio method stays
closer to the a priori CH4 flux in these regions, because it is capable
of simultaneously adjusting the CO2 fluxes. Over tropical South America,
comparison to independent measurements shows that CO2 fields derived
from the ratio method are less realistic than those used in the proxy
method. However, the CH4 fluxes are more realistic, because the impact
of unaccounted systematic uncertainties is more evenly distributed
between CO2 and CH4. The ratio inversion estimates an enhanced CO2
release from tropical South America during the dry season of 2010, which
is in accordance with the findings of Gatti et al. (2014) and Van der
Laan et al. (2015).
The performance of the ratio method is encouraging, because despite the
added nonlinearity due to the assimilation of X-ratio and the
significant increase in the degree of freedom by optimizing CO2 fluxes,
still consistent results are obtained with respect to other CH4
inversions..
BibTeX:
@article{WOS:000376937000018,
  author = {Pandey, Sudhanshu and Houweling, Sander and Krol, Maarten and Aben, Ilse
and Chevallier, Frederic and Dlugokencky, Edward J. and Gatti, Luciana
V. and Gloor, Emanuel and Miller, John B. and Detmers, Rob and Machida,
Toshinobu and Rockmann, Thomas}, title = {Inverse modeling of GOSAT-retrieved ratios of total column
CH4 and CO2 for 2009 and 2010}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2016}, volume = {16}, number = {8}, pages = {5043-5062}, doi = {https://doi.org/10.5194/acp-16-5043-2016} }
Karion, A., Sweeney, C., Miller, J.B., Andrews, A.E., Commane, R., Dinardo, S., Henderson, J.M., Lindaas, J., Lin, J.C., Luus, K.A., Newberger, T., Tans, P., Wofsy, S.C., Wolter, S. and Miller, C.E. Investigating Alaskan methane and carbon dioxide fluxes using
measurements from the CARVE tower
2016 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 16(8), pp. 5383-5398 
article DOI  
Abstract: Northern high-latitude carbon sources and sinks, including those
resulting from degrading permafrost, are thought to be sensitive to the
rapidly warming climate. Because the near-surface atmosphere integrates
surface fluxes over large ( aEuro-500-1000aEuro-km) scales, atmospheric
monitoring of carbon dioxide (CO2) and methane (CH4) mole fractions in
the daytime mixed layer is a promising method for detecting change in
the carbon cycle throughout boreal Alaska. Here we use CO2 and CH4
measurements from a NOAA tower 17aEuro-km north of Fairbanks, AK,
established as part of NASA's Carbon in Arctic Reservoirs Vulnerability
Experiment (CARVE), to investigate regional fluxes of CO2 and CH4 for
2012-2014. CARVE was designed to use aircraft and surface observations
to better understand and quantify the sensitivity of Alaskan carbon
fluxes to climate variability. We use high-resolution meteorological
fields from the Polar Weather Research and Forecasting (WRF) model
coupled with the Stochastic Time-Inverted Lagrangian Transport model
(hereafter, WRF-STILT), along with the Polar Vegetation Photosynthesis
and Respiration Model (PolarVPRM), to investigate fluxes of CO2 in
boreal Alaska using the tower observations, which are sensitive to large
areas of central Alaska. We show that simulated PolarVPRM-WRF-STILT CO2
mole fractions show remarkably good agreement with tower observations,
suggesting that the WRF-STILT model represents the meteorology of the
region quite well, and that the PolarVPRM flux magnitudes and spatial
distribution are generally consistent with CO2 mole fractions observed
at the CARVE tower. One exception to this good agreement is that during
the fall of all 3 years, PolarVPRM cannot reproduce the observed CO2
respiration. Using the WRF-STILT model, we find that average CH4 fluxes
in boreal Alaska are somewhat lower than flux estimates by Chang et al.
(2014) over all of Alaska for May-September 2012; we also find that
enhancements appear to persist during some wintertime periods,
augmenting those observed during the summer and fall. The possibility of
significant fall and winter CO2 and CH4 fluxes underscores the need for
year-round in situ observations to quantify changes in boreal Alaskan
annual carbon balance.
BibTeX:
@article{WOS:000376937000037,
  author = {Karion, Anna and Sweeney, Colm and Miller, John B. and Andrews, Arlyn E.
and Commane, Roisin and Dinardo, Steven and Henderson, John M. and
Lindaas, Jacob and Lin, John C. and Luus, Kristina A. and Newberger, Tim
and Tans, Pieter and Wofsy, Steven C. and Wolter, Sonja and Miller,
Charles E.}, title = {Investigating Alaskan methane and carbon dioxide fluxes using
measurements from the CARVE tower}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2016}, volume = {16}, number = {8}, pages = {5383-5398}, doi = {https://doi.org/10.5194/acp-16-5383-2016} }
Parmentier, F.-J.W., Zhang, W., Mi, Y., Zhu, X., van Huissteden, J., Hayes, D.J., Zhuang, Q., Christensen, T.R. and McGuire, A.D. Rising methane emissions from northern wetlands associated with sea ice
decline
2015 GEOPHYSICAL RESEARCH LETTERS
Vol. 42(17), pp. 7214-7222 
article DOI  
Abstract: The Arctic is rapidly transitioning toward a seasonal sea ice-free
state, perhaps one of the most apparent examples of climate change in
the world. This dramatic change has numerous consequences, including a
large increase in air temperatures, which in turn may affect terrestrial
methane emissions. Nonetheless, terrestrial and marine environments are
seldom jointly analyzed. By comparing satellite observations of Arctic
sea ice concentrations to methane emissions simulated by three
process-based biogeochemical models, this study shows that rising
wetland methane emissions are associated with sea ice retreat. Our
analyses indicate that simulated high-latitude emissions for 2005-2010
were, on average, 1.7 Tg CH4 yr(-1) higher compared to 1981-1990 due to
a sea ice-induced, autumn-focused, warming. Since these results suggest
a continued rise in methane emissions with future sea ice decline,
observation programs need to include measurements during the autumn to
further investigate the impact of this spatial connection on terrestrial
methane emissions.
BibTeX:
@article{WOS:000363411200044,
  author = {Parmentier, Frans-Jan W. and Zhang, Wenxin and Mi, Yanjiao and Zhu,
Xudong and van Huissteden, Jacobus and Hayes, Daniel J. and Zhuang,
Qianlai and Christensen, Torben R. and McGuire, A. David}, title = {Rising methane emissions from northern wetlands associated with sea ice
decline}, journal = {GEOPHYSICAL RESEARCH LETTERS}, year = {2015}, volume = {42}, number = {17}, pages = {7214-7222}, doi = {https://doi.org/10.1002/2015GL065013} }
von Schneidemesser, E., Monks, P.S., Allan, J.D., Bruhwiler, L., Forster, P., Fowler, D., Lauer, A., Morgan, W.T., Paasonen, P., Righi, M., Sindelarova, K. and Sutton, M.A. Chemistry and the Linkages between Air Quality and Climate Change 2015 CHEMICAL REVIEWS
Vol. 115(10), pp. 3856-3897 
article DOI  
BibTeX:
@article{WOS:000355383900006,
  author = {von Schneidemesser, Erika and Monks, Paul S. and Allan, James D. and
Bruhwiler, Lori and Forster, Piers and Fowler, David and Lauer, Axel and
Morgan, William T. and Paasonen, Pauli and Righi, Mattia and
Sindelarova, Katerina and Sutton, Mark A.}, title = {Chemistry and the Linkages between Air Quality and Climate Change}, journal = {CHEMICAL REVIEWS}, year = {2015}, volume = {115}, number = {10}, pages = {3856-3897}, doi = {https://doi.org/10.1021/acs.chemrev.5b00089} }
Feldman, D.R., Collins, W.D., Gero, P.J., Torn, M.S., Mlawer, E.J. and Shippert, T.R. Observational determination of surface radiative forcing by
CO2 from 2000 to 2010
2015 NATURE
Vol. 519(7543), pp. 339+ 
article DOI  
Abstract: The climatic impact of CO2 and other greenhouse gases is usually
quantified in terms of radiative forcing', calculated as the difference
between estimates of the Earth's radiation field from pre-industrial and
presentday concentrations of these gases. Radiative transfer models
calculate that the increase in CO2 since 1750 corresponds to a global
annualmean radiative forcing at the tropopause of 1.82 +/- 0.19W m(-2)
(ref. 2). However, despite widespread scientific discussion and
modelling of the climate impacts of well-mixed greenhouse gases, there
is little direct observational evidence of the radiative impact of
increasing atmospheric CO2. Here we present observationally based
evidence of clear-sky CO2 surface radiative forcing that is directly
attributable to the increase, between 2000 and 2010, of 22 parts per
million atmospheric CO2. The time series of this forcing at the two
locations the Southern Great Plains and the North Slope of Alaska are
derived from Atmospheric Emitted Radiance Interferometer spectra'
together with ancillary measurements and thoroughly corroborated
radiative transfer calculations'. The time series both show
statistically significant trends of 0.2 W m(-2) per decade (with
respective uncertainties of +/- 0.06 W m(-2) per decade and 0.07 W m(-2)
per decade) and have seasonal ranges of 0.1-0.2W m(-2). This is
approximately ten per cent of the trend in downwelling longwave
radiation'''. These results confirm theoretical predictions of the
atmospheric greenhouse effect due to anthropogenic emissions, and
provide empirical evidence of how rising CO2 levels, mediated by
temporal variations due to photosynthesis and respiration, are affecting
the surface energy balance.
BibTeX:
@article{WOS:000351171900038,
  author = {Feldman, D. R. and Collins, W. D. and Gero, P. J. and Torn, M. S. and
Mlawer, E. J. and Shippert, T. R.}, title = {Observational determination of surface radiative forcing by
CO2 from 2000 to 2010}, journal = {NATURE}, year = {2015}, volume = {519}, number = {7543}, pages = {339+}, doi = {https://doi.org/10.1038/nature14240} }
Turner, A.J., Jacob, D.J., Wecht, K.J., Maasakkers, J.D., Lundgren, E., Andrews, A.E., Biraud, S.C., Boesch, H., Bowman, K.W., Deutscher, N.M., Dubey, M.K., Griffith, D.W.T., Hase, F., Kuze, A., Notholt, J., Ohyama, H., Parker, R., Payne, V.H., Sussmann, R., Sweeney, C., Velazco, V.A., Warneke, T., Wennberg, P.O. and Wunch, D. Estimating global and North American methane emissions with high spatial
resolution using GOSAT satellite data
2015 ATMOSPHERIC CHEMISTRY AND PHYSICS
Vol. 15(12), pp. 7049-7069 
article DOI  
Abstract: We use 2009-2011 space-borne methane observations from the Greenhouse
Gases Observing SATellite (GOSAT) to estimate global and North American
methane emissions with 4A degrees x 5A degrees and up to 50 km x 50 km
spatial resolution, respectively. GEOS-Chem and GOSAT data are first
evaluated with atmospheric methane observations from surface and tower
networks (NOAA/ESRL, TCCON) and aircraft (NOAA/ESRL, HIPPO), using the
GEOS-Chem chemical transport model as a platform to facilitate
comparison of GOSAT with in situ data. This identifies a high-latitude
bias between the GOSAT data and GEOS-Chem that we correct via quadratic
regression. Our global adjoint-based inversion yields a total methane
source of 539 Tg a(-1) with some important regional corrections to the
EDGARv4.2 inventory used as a prior. Results serve as dynamic boundary
conditions for an analytical inversion of North American methane
emissions using radial basis functions to achieve high resolution of
large sources and provide error characterization. We infer a US
anthropogenic methane source of 40.2-42.7 Tg a(-1), as compared to
24.9-27.0 Tg a(-1) in the EDGAR and EPA bottom-up inventories, and
30.0-44.5 Tg a(-1) in recent inverse studies. Our estimate is supported
by independent surface and aircraft data and by previous inverse studies
for California. We find that the emissions are highest in the
southern-central US, the Central Valley of California, and Florida
wetlands; large isolated point sources such as the US Four Corners also
contribute. Using prior information on source locations, we attribute
29-44 % of US anthropogenic methane emissions to livestock, 22-31 % to
oil/gas, 20 % to landfills/wastewater, and 11-15 % to coal. Wetlands
contribute an additional 9.0-10.1 Tg a(-1).
BibTeX:
@article{WOS:000357117500034,
  author = {Turner, A. J. and Jacob, D. J. and Wecht, K. J. and Maasakkers, J. D.
and Lundgren, E. and Andrews, A. E. and Biraud, S. C. and Boesch, H. and
Bowman, K. W. and Deutscher, N. M. and Dubey, M. K. and Griffith, D. W.
T. and Hase, F. and Kuze, A. and Notholt, J. and Ohyama, H. and Parker,
R. and Payne, V. H. and Sussmann, R. and Sweeney, C. and Velazco, V. A.
and Warneke, T. and Wennberg, P. O. and Wunch, D.}, title = {Estimating global and North American methane emissions with high spatial
resolution using GOSAT satellite data}, journal = {ATMOSPHERIC CHEMISTRY AND PHYSICS}, year = {2015}, volume = {15}, number = {12}, pages = {7049-7069}, doi = {https://doi.org/10.5194/acp-15-7049-2015} }
Chang, R.Y.W., Miller, C.E., Dinardo, S.J., Karion, A., Sweeney, C., Daube, B.C., Henderson, J.M., Mountain, M.E., Eluszkiewicz, J., Miller, J.B., Bruhwiler, L.M.P. and Wofsy, S.C. Methane emissions from Alaska in 2012 from CARVE airborne observations 2014 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF
AMERICA
Vol. 111(47), pp. 16694-16699 
article DOI  
Abstract: We determined methane (CH4) emissions from Alaska using airborne
measurements from the Carbon Arctic Reservoirs Vulnerability Experiment
(CARVE). Atmospheric sampling was conducted between May and September
2012 and analyzed using a customized version of the polar weather
research and forecast model linked to a Lagrangian particle dispersion
model (stochastic time-inverted Lagrangian transport model). We
estimated growing season CH4 fluxes of 8 +/- 2 mg CH4.m(-2).d(-1)
averaged over all of Alaska, corresponding to fluxes from wetlands of
56(-13)(+22) mg CH4.m(-2).d(-1) if we assumed that wetlands are the only
source from the land surface (all uncertainties are 95% confidence
intervals from a bootstrapping analysis). Fluxes roughly doubled from
May to July, then decreased gradually in August and September.
Integrated emissions totaled 2.1 +/- 0.5 Tg CH4 for Alaska from May to
September 2012, close to the average (2.3; a range of 0.7 to 6 Tg CH4)
predicted by various land surface models and inversion analyses for the
growing season. Methane emissions from boreal Alaska were larger than
from the North Slope; the monthly regional flux estimates showed no
evidence of enhanced emissions during early spring or late fall,
although these bursts may be more localized in time and space than can
be detected by our analysis. These results provide an important baseline
to which future studies can be compared.
BibTeX:
@article{WOS:000345662700026,
  author = {Chang, Rachel Y. -W. and Miller, Charles E. and Dinardo, Steven J. and
Karion, Anna and Sweeney, Colm and Daube, Bruce C. and Henderson, John
M. and Mountain, Marikate E. and Eluszkiewicz, Janusz and Miller, John
B. and Bruhwiler, Lori M. P. and Wofsy, Steven C.}, title = {Methane emissions from Alaska in 2012 from CARVE airborne observations}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF
AMERICA}, year = {2014}, volume = {111}, number = {47}, pages = {16694-16699}, doi = {https://doi.org/10.1073/pnas.1412953111} }
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