Incorporating methane isotopologues alters tropical and subtropical methane emission estimates

measurements. The methane-isotopic inversion yields total emissions of 623 [585-643] Tg/y, slightly higher than the methane-only inversion. Incorporating isotopic constraints leads to a redistribution of emissions in tropical and subtropical regions. Compared with the methane-only inversion, the methane-isotopic inversion indicates that emission estimates increase by 26 [-3-27] Tg/y in East Asia (primarily China), 7 [-1-8] Tg/y in South Asia (primarily India), and 5 [-3-10] Tg/y in central Africa, while decreasing by 5 [-6-7] Tg/y in Amazon Basin and 12 [-14-20] Tg/y elsewhere. This points to a stronger anthropogenic contribution to the post-2019 methane budget, including higher fossil emissions in China and slightly less wetland emissions in the Amazon Basin. The methane-isotopic inversion also alters inferred emission seasonality, showing less seasonality in China compared with the methane-only inversion, weaker coal-mine phase-out signals, and a delayed summer peak in Southeast Asia, pointing to sources missing from current inventories.