Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 114, Issue 36, Pages 9647-9652Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1618765114
Keywords
global warming potential; climate feedbacks; inundation; radiative forcing; climate mitigation
Categories
Funding
- Montana State University Information Technology Research Cyberinfrastructure
- Competence Center Environment and Sustainability (CCES) Project Modeling and Experiments on Land-Surface Interactions with Atmospheric Chemistry and Climate Phase 2 (MAIOLICA2) [42-01]
- Chinese Academy of Sciences (CAS) Project Big Earth Data Engineering
- National Natural Science Foundation of China [T411391001, 91425303]
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Wetland methane (CH4) emissions are the largest natural source in the global CH4 budget, contributing to roughly one third of total natural and anthropogenic emissions. As the second most important anthropogenic greenhouse gas in the atmosphere after CO2, CH4 is strongly associated with climate feedbacks. However, due to the paucity of data, wetland CH4 feedbacks were not fully assessed in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The degree to which future expansion of wetlands and CH4 emissions will evolve and consequently drive climate feedbacks is thus a question of major concern. Here we present an ensemble estimate of wetland CH4 emissions driven by 38 general circulation models for the 21st century. We find that climate change-induced increases in boreal wetland extent and temperature-driven increases in tropical CH4 emissions will dominate anthropogenic CH4 emissions by 38 to 56% toward the end of the 21st century under the Representative Concentration Pathway (RCP2.6). Depending on scenarios, wetland CH4 feedbacks translate to an increase in additional global mean radiative forcing of 0.04W.m(-2) to 0.19W.m(-2) by the end of the 21st century. Under the worst-case RCP8.5 scenario, with no climate mitigation, boreal CH4 emissions are enhanced by 18.05 Tg to 41.69 Tg, due to thawing of inundated areas during the cold season (December to May) and rising temperature, while tropical CH4 emissions accelerate with a total increment of 48.36 Tg to 87.37 Tg by 2099. Our results suggest that climate mitigation policies must consider mitigation of wetland CH4 feedbacks to maintain average global warming below 2 degrees C.
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