Isotopic constraints in methane inversions reveal larger trends in wetland emissions with improved linkage to terrestrial water storage

Abstract Accurately separating the contributions of different sources to recent atmospheric methane (CH 4 ) growth is crucial for better quantifying the present and future responses of CH 4 emissions to changing climate and anthropogenic activity. Here, we run atmospheric inversions to assess global and regional CH 4 emissions from microbial, fossil, and pyrogenic sources from 2000 to 2022, using measurements of atmospheric CH 4 and its stable carbon isotope ratio ( 13 C: 12 C, expressed relative to a standard as δ 13 C-CH 4 ). We confirm that global total CH 4 emissions has increased by 15% from 2000 to 2022, with dominated contribution from microbial emissions. Both microbial and fossil emissions increased during 2007–2013 relative to 2000–2006, with the largest contributions from temperate Asia. From 2014–2017, microbial emissions from tropical regions, particularly South America and Africa, were the dominant driver of the overall increase, while fossil emissions remained stable in Europe and North America. Between 2020 and 2022, microbial emissions surged in the African and Asian tropics, whereas fossil emissions declined across most industrial regions. Notably, inversions constrained only by CH 4 observations did not capture the decline in fossil emissions during 2020–2022, a decline potentially related to the COVID-19 pandemic, policy-driven changes, and decreases in CH 4 emissions intensity, highlighting the critical role of isotopic measurements in independently verifying changes in fossil emissions. Further, our inversion with isotopic constraints estimates a more prominent increase in wetland emissions that is 20–30% more strongly correlated with variations in terrestrial water storage during 2003–2022, demonstrating the importance of climate-driven natural sources in explaining long-term CH 4 growth.

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Publication Details

Journal
Nature Communications
Published
2026-06-29
DOI
https://doi.org/10.1038/s41467-026-74777-4
Primary Topic
Atmospheric and Environmental Gas Dynamics
Type
article
Field-Weighted Citation Impact
0.00

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article

Isotopic constraints in methane inversions reveal larger trends in wetland emissions with improved linkage to terrestrial water storage

Taku Umezawa, Łukasz Chmura, Sebastien Christophe Biraud, John Bharat Miller et al.
Nature Communications
Atmospheric and Environmental Gas Dynamics
article

Isotopic constraints in methane inversions reveal larger trends in wetland emissions with improved linkage to terrestrial water storage

Taku Umezawa, Łukasz Chmura, Sebastien Christophe Biraud, John Bharat Miller, Sourish Basu, A. E. Andrews, Giulia Zazzeri, Shinji Morimoto, Irène Xueref-Rémy, Youmi Oh, Licheng Liu, Xin Lan, Martin Steinbacher, Santanu Halder, Élise-Andrée Guérette, Ben Riddell‐Young, Sylvia Michel, Lori Bruhwiler, Elena Kozlova, Simonetta Montaguti, Tatiana Di lorio, Ken Schuldt
article en

Abstract

Abstract Accurately separating the contributions of different sources to recent atmospheric methane (CH 4 ) growth is crucial for better quantifying the present and future responses of CH 4 emissions to changing climate and anthropogenic activity. Here, we run atmospheric inversions to assess global and regional CH 4 emissions from microbial, fossil, and pyrogenic sources from 2000 to 2022, using measurements of atmospheric CH 4 and its stable carbon isotope ratio ( 13 C: 12 C, expressed relative to a standard as δ 13 C-CH 4 ). We confirm that global total CH 4 emissions has increased by 15% from 2000 to 2022, with dominated contribution from microbial emissions. Both microbial and fossil emissions increased during 2007–2013 relative to 2000–2006, with the largest contributions from temperate Asia. From 2014–2017, microbial emissions from tropical regions, particularly South America and Africa, were the dominant driver of the overall increase, while fossil emissions remained stable in Europe and North America. Between 2020 and 2022, microbial emissions surged in the African and Asian tropics, whereas fossil emissions declined across most industrial regions. Notably, inversions constrained only by CH 4 observations did not capture the decline in fossil emissions during 2020–2022, a decline potentially related to the COVID-19 pandemic, policy-driven changes, and decreases in CH 4 emissions intensity, highlighting the critical role of isotopic measurements in independently verifying changes in fossil emissions. Further, our inversion with isotopic constraints estimates a more prominent increase in wetland emissions that is 20–30% more strongly correlated with variations in terrestrial water storage during 2003–2022, demonstrating the importance of climate-driven natural sources in explaining long-term CH 4 growth.

Nature Communications
National Agency for New Technologies, Energy and Sustainable Economic Development (IT), Jagiellonian University (PL), CSIRO Oceans and Atmosphere (AU), Commonwealth Scientific and Industrial Research Organisation (AU), Centre National de la Recherche Scientifique (FR), University of Minnesota (US), National Oceanic and Atmospheric Administration (US), Lawrence Berkeley National Laboratory (US), Cooperative Institute for Research in Environmental Sciences (US), Institute of Arctic and Alpine Research (US), University of Colorado Boulder (US), National Institute for Environmental Studies (JP), Tohoku University (JP), University of Exeter (GB), Institute of Atmospheric Sciences and Climate (IT), Ricerca sul Sistema Energetico (Italy) (IT), Institute of Meteorology and Water Management (PL), Institut Méditerranéen de Biodiversité et d'Ecologie Marine et Continentale (FR), Earth System Science Interdisciplinary Center (US), Institut de Recherche pour le Développement (FR), University of Maryland, College Park (US), AGH University of Krakow (PL), Swiss Federal Laboratories for Materials Science and Technology (CH)
National Aeronautics and Space Administration, U.S. Department of Commerce, National Institute of Water and Atmospheric Research, Ministry of Education, Culture, Sports, Science and Technology, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Polska Akademia Nauk, National Institute of Polar Research, National Oceanic and Atmospheric Administration, Climate Program Office
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