Project Goals (CarbonTracker-CH4)

To produce quantitative estimates of global atmospheric methane emissions that are consistent with observed patterns of CH4 and its stable carbon isotope in the atmosphere.

A Tool for Science and Policy

CarbonTracker-CH4 is a prototype Monitoring, Measurement, Reporting and Verfication (MMRV) modeling system that can, together with long-term monitoring of atmospheric CH4 and its stable carbon isotope, δ13C-CH4, help us to improve our understanding of how methane emissions are responding to a changing climate and human activities, including fossil fuel use and agriculture. The open access to all CarbonTracker-CH4 results means that everyone can access our results, suggest improvements, and use our work to further understanding of atmospheric CH4. We hope that this will lead to an improved ability to monitor emissions, reconcile estimates with emission inventories, and verify that emission reduction strategies are effective. Furthermore, we propose that long-term estimates of global CH4 emissions may help us to detect feedbacks between CH4 and climate change, and may also help to improve models used to make projections of future climate.

A Community Effort

CarbonTracker-CH4 is intended to be a tool for the community and we welcome feedback and collaboration. Our ability to accurately track methane with greater spatial and temporal detail is dependent on our ability to collect enough measurements and to obtain enough air samples to characterize variability in the atmosphere. For example, our models suggest that observations from tall communication towers (>200m) can tell us about carbon uptake and emission over an area of only several hundred kilometers, but the high frequency of our tower samples improve our ability to resolve temporal variability in emissions. The map of observation sites below shows how sparse the current network is. Especially, only 3% of data points of CH4 measurements concurrently have its stable carbon isotope measurements (δ13C-CH4, red color in the map).

One way to join this effort is by contributing measurements. Regular air samples collected from the surface, towers or aircraft could help us to improve our estimates and are greatly appreciated. We also hope to increase the use of high frequency measurements. Another way to contribute our effort is to contribute estimates of methane fluxes from your inventories or process models that we can test in CarbonTracker-CH4. Please contact us if you would like to get involved and collaborate!

carbontracker ch4 map
carbontracker ch4 map
Locations of CarbonTracker-CH4 (top) global and (bottom) North American observation sites


CarbonTracker is updated periodically to include new data and model improvements. The first version of CarbonTracker-CH4 was published to the Global Monitoring Laboratory's website in 2014 (Bruhwiler et al., 2014). We have recently updated our CarbonTracker-CH4 inversion system by jointly assimilating measurements of CH4 and δ13C-CH4, optimizing fluxes at the transport model’s horizontal resolution, and incorporating spatially- and temporally-resolved δ13C-CH4 signatures of sources. Furthermore, the system has been extended to estimate fluxes through 2021. The previous versions are available, and notes can be found at noted.

Other atmospheric species and their possible roles in constraining the atmospheric carbon budget

Many laboratories making high-accuracy CH4 observations also make many other measurements of the same air, typically other trace gases such as CO2, nitrous oxide (N2O), sulfur hexafluoride (SF6), carbon monoxide (CO) and isotopic ratios of CO2 and CH4. These measurements are usually made as dry air mass mole fractions, for reasons explained here. For example, SF6 can be an excellent tracer for evaluating modeled atmospheric transport. CO can inform about wildfire emissions, and δ13C-CH4 can help us to attribute CH4 to fossil fuel or microbial sources.

CarbonTracker is a NOAA contribution to the North American Carbon Program