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Role of atmospheric oxidation in recent methane growth

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)5373-5377
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number21
Early online date17 Apr 2017
DOIs
DateAccepted/In press - 16 Mar 2017
DateE-pub ahead of print - 17 Apr 2017
DatePublished (current) - 23 May 2017

Abstract

The growth in global methane (CH4) concentration, which had been ongoing since the industrial revolution, stalled around the year 2000 before resuming globally in 2007. We evaluate the role of the hydroxyl radical (OH), the major CH4 sink, in the recent CH4 growth. We also examine the influence of systematic uncertainties in OH concentrations on CH4 emissions inferred from atmospheric observations. We use observations of 1,1,1-trichloroethane (CH3CCl3), which is lost primarily through reaction with OH, to estimate OH levels as well as CH3CC3 emissions, which have uncertainty that previously limited the accuracy of OH estimates. We find a 64–70% probability that a decline in OH has contributed to the post-2007 methane rise. Our median solution suggests that CH4 emissions increased relatively steadily during the late 1990s and early 2000s, after which growth was more modest. This solution obviates the need for a sudden statistically significant change in total CH4 emissions around the year 2007 to explain the atmospheric observations and can explain some of the decline in the atmospheric 13CH4/12CH4 ratio and the recent growth in C2H6. Our approach indicates that significant OH-related uncertainties in the CH4 budget remain, and we find that it is not possible to implicate, with a high degree of confidence, rapid global CH4 emissions changes as the primary driver of recent trends when our inferred OH trends and these uncertainties are considered.

    Research areas

  • methane, hydroxyl, inversion, methyl chloroform, 1,1,1-trichloroethane

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  • Full-text PDF (accepted author manuscript)

    Rights statement: This is the author accepted manuscript (AAM). The final published version (version of record) is available online via PNAS at http://www.pnas.org/content/early/2017/04/11/1616426114. Please refer to any applicable terms of use of the publisher.

    Accepted author manuscript, 393 KB, PDF-document

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