A Gridded Inventory of Annual 2012–2018 U.S. Anthropogenic Methane Emissions

Reductions in methane emissions are an important factor in reaching collective climate goals, such as limiting global meanwarming to below 2 °C.1,2 Inventories of greenhouse gas (GHG) emissions, including methane, are key to supporting andtracking these goals by, for example, supporting the develop-ment and tracking of domestic mitigation policies,3 NationallyDetermined Contributions, and informing the Paris Agreement’s Global Stocktake.1 Under the 1992 United Nations Framework Convention on Climate Change (UNFCCC),4 Parties are required to report inventories of anthropogenic GHG emissions and sinks using internationally agreed-upon methodological guidance from the Intergovernmental Panel on Climate Change (IPCC).5,6 The quality of GHG inventory estimates is dependent on the underlying emission mechanisms and the robustness of methods and data used. In some cases, particularly for some methane sources, limited or uncertain underlying data can result in large uncertainties.6 As described in the 2019 Refinements to the IPCC GHG Guidelines,6 estimates can be compared to emissions derived from independent atmospheric observations, as a part of a broader strategy to evaluate and improve inventories. Comparisons with observations can provide information to identify key areas for refinement, particularly for methane, as emissions are largely from fugitive and biological sources, which can be more challenging to quantify than other GHG sources. Here, we present the first time series of gridded U.S. anthropogenic methane emissions, consistent with national U.S. UNFCCCreporting, to facilitate these observation-based comparisons.