Abstract
Annual increases in atmospheric methane have reached record highs over the past five years, yet the underlying processes and regional sources remain uncertain. Here we quantify the average 2019-2021 global methane budget using Bayesian 4D-Var inversions that assimilate satellite methane retrievals and in-situ δ13C-CH4 and δD-CH4 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.
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Acknowledgements
We thank Sylvia Englund Michel and Justin Reid Clark for their helpful suggestions. We also thank the US National Oceanic and Atmospheric Administration (NOAA) for providing methane isotopic measurements and the Netherlands Institute for Space Research (SRON) teams for providing TROPOMI methane observations. Our research was supported by the Gordon and Betty Moore Foundation through Grants GBMF5439 ‘Advancing Understanding of the Global Methane Cycle’ and GBMF11519 ‘Advancing the understanding of methane emissions from tropical wetlands’ to Stanford University, and Stanford’s Global Methane Office for the Global Carbon Project. X.Y. and R.B.J. acknowledge additional funding through the framework of UNEP’s International Methane Emissions Observatory (IMEO) (#DTIE21-EN3143) to Stanford University. X.Y. acknowledges funding from an IBM CEAIS Seed Grant to the State University of New York at Albany (award no. 102522). D.K.H. acknowledges support from the United States Environmental Protection Agency (EPA, 84062601) and the US Department of Energy (DOE, DE-FE0032305).
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Yu, X., Canadell, J.G., Henze, D.K. et al. Incorporating methane isotopologues alters tropical and subtropical methane emission estimates. Nat Commun (2026). https://doi.org/10.1038/s41467-026-72668-2
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DOI: https://doi.org/10.1038/s41467-026-72668-2
