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Interpreting contemporary trends in atmospheric methane

Turner, Alexander J. and Frankenberg, Christian and Kort, Eric A. (2019) Interpreting contemporary trends in atmospheric methane. Proceedings of the National Academy of Sciences of the United States of America, 116 (8). pp. 2805-2813. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:20190208-094453400

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Abstract

Atmospheric methane plays a major role in controlling climate, yet contemporary methane trends (1982–2017) have defied explanation with numerous, often conflicting, hypotheses proposed in the literature. Specifically, atmospheric observations of methane from 1982 to 2017 have exhibited periods of both increasing concentrations (from 1982 to 2000 and from 2007 to 2017) and stabilization (from 2000 to 2007). Explanations for the increases and stabilization have invoked changes in tropical wetlands, livestock, fossil fuels, biomass burning, and the methane sink. Contradictions in these hypotheses arise because our current observational network cannot unambiguously link recent methane variations to specific sources. This raises some fundamental questions: (i) What do we know about sources, sinks, and underlying processes driving observed trends in atmospheric methane? (ii) How will global methane respond to changes in anthropogenic emissions? And (iii), What future observations could help resolve changes in the methane budget? To address these questions, we discuss potential drivers of atmospheric methane abundances over the last four decades in light of various observational constraints as well as process-based knowledge. While uncertainties in the methane budget exist, they should not detract from the potential of methane emissions mitigation strategies. We show that net-zero cost emission reductions can lead to a declining atmospheric burden, but can take three decades to stabilize. Moving forward, we make recommendations for observations to better constrain contemporary trends in atmospheric methane and to provide mitigation support.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1073/pnas.1814297116DOIArticle
http://workshop.caltech.edu/methane/Related ItemWorkshop
ORCID:
AuthorORCID
Turner, Alexander J.0000-0003-1406-7372
Frankenberg, Christian0000-0002-0546-5857
Kort, Eric A.0000-0003-4940-7541
Additional Information:© 2019 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). PNAS published ahead of print February 7, 2019. Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved January 9, 2019 (received for review August 18, 2018) We thank the Linde Center for Global Environmental Science at California Institute of Technology for supporting the workshop that made this study possible. We are extremely grateful to the many participants in said workshop (“Toward Addressing Major Gaps in the Global Methane Budget”; workshop.caltech.edu/methane/): A. A. Bloom, P. Bousquet, L. M. Bruhwiler, G. Chadwick, P. Crill, G. Etiope, S. Houweling, D. J. Jacob, F. Keppler, J. D. Maasakkers, C. Miller, S. Naus, E. Nisbet, M. Okumua, B. Poulter, M. Prather, J. Randerson, K. M. Saad, S. Sander, D. Schimel, C. Sweeney, K. Verhulst, D. Wunch, and Y. Yin. The insights and conversations from this group improved this study. Finally, this work would not have been possible without the tireless efforts and public data sharing of scientists making long-term measurements, pursuing atmospheric modeling, and developing inventories: specifically, the NOAA/Earth Systems Research Lab (ESRL) Global Greenhouse Gas Reference Network and AGAGE for CH_4; R. Sussmann and D. Smale for XC_2H_6; NOAA/Institute of Arctic and Alpine Research (INSTARR), University of California, Irvine, University of Washington, and University of Heidelberg for δ^(13)C-CH_4; A. A. Bloom for the Wetland Methane Emissions and Uncertainty (WetCHARTs) inventory; B. Poulter for the GCP wetlands; and J. R. Melton for The Wetland and Wetland CH_4 Inter-comparison of Models Project (WetCHIMP). A.J.T. is supported as a Miller Fellow with the Miller Institute for Basic Research in Science at University of California, Berkeley. A.J.T., C.F., and E.A.K. contributed equally to this work. Author contributions: A.J.T., C.F., and E.A.K. designed research, performed research, analyzed data, and wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission.
Funders:
Funding AgencyGrant Number
Miller Institute for Basic Research in ScienceUNSPECIFIED
Ronald And Maxine Linde Center for Global Environmental ScienceUNSPECIFIED
Subject Keywords:methane trends | greenhouse gas mitigation | tropospheric oxidative capacity
Record Number:CaltechAUTHORS:20190208-094453400
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190208-094453400
Official Citation:Interpreting contemporary trends in atmospheric methane Alexander J. Turner, Christian Frankenberg, Eric A. Kort Proceedings of the National Academy of Sciences Feb 2019, 116 (8) 2805-2813; DOI: 10.1073/pnas.1814297116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92788
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:08 Feb 2019 17:56
Last Modified:20 Feb 2019 15:48

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