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. We quantify methane emissions and their 2010–2017 trends by sector in thecontiguous United States (CONUS), Canada, and Mexico by inverse analysis of insitu (GLOBALVIEWplus CH4 ObsPack) and satellite (GOSAT) atmosphericmethane observations. The inversion uses as a prior estimate the nationalanthropogenic emission inventories for the three countries reported by the USEnvironmental Protection Agency (EPA), Environment and Climate Change Canada(ECCC), and the Instituto Nacional de Ecología y Cambio Climático(INECC) in Mexico to the United Nations Framework Convention on Climate Change(UNFCCC) and thus serves as an evaluation of these inventories in terms oftheir magnitudes and trends. Emissions are optimized with a Gaussian mixturemodel (GMM) at 0.5∘×0.625∘ resolution and forindividual years. Optimization is done analytically using lognormal errorforms. This yields closed-form statistics of error covariances and informationcontent on the posterior (optimized) estimates, allows better representationof the high tail of the emission distribution, and enables construction of alarge ensemble of inverse solutions using different observations andassumptions. We find that GOSAT and in situ observations are largelyconsistent and complementary in the optimization of methane emissions forNorth America. Mean 2010–2017 anthropogenic emissions from our base GOSAT + in situ inversion, with ranges from the inversion ensemble, are 36.9(32.5–37.8) Tg a−1 for CONUS, 5.3 (3.6–5.7) Tg a−1for Canada, and 6.0 (4.7–6.1) Tg a−1 for Mexico. These are higherthan the most recent reported national inventories of 26.0 Tg a−1for the US (EPA), 4.0 Tg a−1 for Canada (ECCC), and5.0 Tg a−1 for Mexico (INECC). The correction in all threecountries is largely driven by a factor of 2 underestimate in emissions fromthe oil sector with major contributions from the south-central US, westernCanada, and southeastern Mexico. Total CONUS anthropogenic emissions in ourinversion peak in 2014, in contrast to the EPA report of a steady decreasingtrend over 2010–2017. This reflects offsetting effects of increasingemissions from the oil and landfill sectors, decreasing emissions from the gassector, and flat emissions from the livestock and coal sectors. We finddecreasing trends in Canadian and Mexican anthropogenic methane emissions overthe 2010–2017 period, mainly driven by oil and gas emissions. Our bestestimates of mean 2010–2017 wetland emissions are 8.4(6.4–10.6) Tg a−1 for CONUS, 9.9 (7.8–12.0) Tg a−1for Canada, and 0.6 (0.4–0.6) Tg a−1 for Mexico. Wetlandemissions in CONUS show an increasing trend of +2.6 (+1.7 to+3.8)% a−1 over 2010–2017correlated with precipitation.

atmospheric chemistry and physics

Methane emissions in the United States, Canada, and Mexico: evaluation of national methane emission inventories and 2010–2017 sectoral trends by inverse analysis of in situ (GLOBALVIEWplus CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; ObsPack) and satellite (GOSAT) atmospheric observations