General information on WMO/IAEA Round Robin experiments. For experimental details and recommended guidelines, please click on Guidelines.

Important! The Round Robin experimental setup has been modified in an effort to complete the experiment in one year. These changes are summarized in Guidelines.


WMO/IAEA Round Robin experiments typically occur every 3-4 years. Experiments have historically taken 2-3 years to complete depending on the number of participants. A new Round Robin experiment typically begins within a year of completion of the last experiment.


Laboratories that make ongoing, high-precision measurements of atmospheric CO2 and maintain a laboratory CO2 scale are encouraged to participate in the WMO/IAEA Round Robin experiments. It is important, however, to express your intent to participate as soon as possible to ensure inclusion in the next experiment (see Guidelines for further details).


There is no Round Robin participation fee. Participating labs are responsible for costs associated with receiving the WMO Round Robin cylinders from their country customs office and shipping them on to the next participant.


Logistics for the WMO/IAEA Round Robin experiments are coordinated by NOAA. The NOAA coordinating team will assign each participant to a circuit. The circuits are designed to minimize shipping costs and expedite completion of the experiment. Laboratories in each circuit will receive a set of 2 Round Robin cylinders. Participants will know the nominal CO2 range of each cylinder in their circuit. The NOAA team will also assign values for other trace gas species and isotopes including CH4, CO, H2, N2O, SF6, O2/N2, and δ13C and δ18O of CO2.


The Round Robin measurement timetable is set by the NOAA team and depends on the number of participants, the number of measured trace gas species by each participant, and the location of the participating labs. The timetable identifies the order in which laboratories will receive the WMO cylinders within each circuit. The timetable may need to be revised while the experiment is underway due to unforeseen problems. If a revision to the schedule is required, participants who have yet to measure the cylinders will be notified.

Allotted Measurement Time

Participants will be allocated a certain amount of time to complete their measurements once they receive the WMO cylinders. The allotted time depends on how many trace gas species and isotopes they intend to measure. Participation in the Round Robin requires your agreement to forward the WMO cylinders on to the next scheduled participant at the end of your allotted time even if all measurements have not been completed (see Guidelines for further details).


Participants will report their results on-line. Results will include a single measurement value and estimated uncertainty for each trace gas or isotope measured, cylinder pressure, measurement date, reported scale, and detection method. Participants are also required to report the dates on which the WMO cylinders arrive at their lab and are shipped from their lab. (see Guidelines for further details). Note: Values reported or updated after the experiment closure date are logged but will not be included in the summary of comparison results.

A user name and password are required to report results and update/verify account information. The NOAA team will provide current Round Robin participants with a username (if one does not already exist) and a password (valid until the start of the next Round Robin). Participants will need to update their account information as soon as possible after receiving account access details.


The NOAA team will track progress using the timetable and reported cylinder arrival and shipping information. Participants will receive automatic notification when WMO cylinders are expected to arrive at their location and when they are due to be shipped to the next participant.


The NOAA team will post the experiment closure date to this web site as soon as it can be determined. To have results included in the experiment summary report, participants must report their measurements no later than the closure date. Note: Values reported or updated after the experiment closure date are logged but will not be included in the summary of comparison results.


Once the current Round Robin experiment is closed, the WMO/IAEA Round Robin referee will review the reported results for errors. The referee will contact participants as needed. Results will be archived and available in graphical and tabular form from this web site once the results are finalized by the referee (see Archived Results for archived Round Robin comparison results).