Bottom‐Up Evaluation of the Methane Budget in Asia and Its Subregions

A comprehensive methane (CH4) budget, including spatial and temporal patterns of sources and sinks, is pivotal for effective climatic mitigation and prediction. This study used a bottom‐up approach to evaluate the CH4 budget of Asia during 1970–2021. Natural sources and sinks were evaluated using a process‐based biogeochemical model and with ground and satellite observations. Anthropogenic sources were evaluated using emission inventories produced by socioeconomic studies. During the 1970s and 2010s, anthropogenic emissions accounted for 78% and 84% of the emitted total CH4 budget of 140.2 and 207.6 Tg CH4 yr−1, respectively. Anthropogenic sources were responsible for a 49% increase in total emissions. During 2001–2021, Central, East, South, Southeast, and West Asia accounted for 3.3%, 35.1%, 25.6%, 23.1%, and 13.0%, respectively, of Asian emissions. Sectoral compositions and temporal variations differed among subregions. Emissions from paddy field soils in Asia were smaller in 2021 (33.6 Tg CH4 yr−1) than in 1970 (39.2 Tg CH4 yr−1) because of changes in agricultural production. Among natural sources, wetlands accounted for 63% of total emissions in East Asia, but geological emissions predominated in Central and West Asia. Interannual variability of the net CH4 budget was mainly due to wetland and biomass burning emissions, whereas decadal variability was due to anthropogenic sectors. δ13C‐CH4 and isoflux analysis of sector‐specific fluxes and isotopic ratios indicated the effects of the regional budget on atmospheric trends. Bottom‐up evaluations of regional budgets can provide information critical to the Global Stocktake of the Paris Agreement, the Global Methane Pledge, and other related actions. Key Points We used a bottom‐up approach to estimate methane emissions from Asia and their spatial distribution during 1970–2021 Asia was estimated to be a net source of methane of 207.6 Tg CH4 yr−1 in the 2010s, 84% of which came from anthropogenic sources The estimated net emissions and their δ13C signature suggested that Asia made a large contribution to atmospheric methane trends