Significant Overestimation in Anthropogenic Methane Emissions in China

China, as the largest contributor to global anthropogenic methane (CH4) emissions, has pledged to reduce its global CH4 emissions by 30% in 2030 compared to 2022 levels. Accurate estimation of CH4 emissions is crucial for climate prediction and mitigation policies but poses a significant challenge for methods relying solely on economic statistics and emission factors. In this study, we developed a regional carbon assimilation system (RegGCAS) to integrate TROPOMI XCH4 observations for inferring daily CH4 emissions across China. Our estimated national total CH4 emission for 2022 was 45 Tg·yr⁻¹, approximately 35% lower than the widely used EDGARv8 inventory (prior estimate). Notable reductions were primarily observed in Northern China, with only sporadic increases in Shanxi Province, which contributes one-third of China's coal production. Increases were primarily concentrated in the Sichuan Basin, the southeast coastal provinces, and Heilongjiang Province in Northeast China. The optimized CH4 emission estimate exhibited more pronounced seasonal variations, with a significant decrease in emissions during winter. However, constraints on emissions in summer were limited due to the lack of observational data. Posterior simulations demonstrated better consistency with both TROPOMI XCH4 observations and ground-based observations. These findings enhance our understanding of the spatiotemporal patterns of CH4 emissions in China.