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Reconciling the changes in atmospheric-methane sources and sinks between the Last Glacial Maximum and the pre-industrial era

By J.G. Levine, E.W. Wolff, A.E. Jones, L.C. Sime, P.J. Valdes, A.T. Archibald, G.D. Carver, N.J. Warwick and J.A. Pyle

Abstract

We know from the ice record that the concentration of\ud atmospheric methane, [CH4], at the Last Glacial Maximum\ud (LGM) was roughly half that in the pre-industrial era (PI), buthow much of the difference was source-driven, and how\ud much was sink-driven, remains uncertain. Recent developments\ud include: a higher estimate of the LGM-PI change in\ud methane emissions from wetlands―the dominant, natural\ud methane source; and the possible recycling of OH consumed\ud in isoprene oxidation―the principal methane sink.\ud Here, in view of these developments, we use an atmospheric\ud chemistry-transport model to re-examine the main factors\ud affecting OH during this period: changes in air temperature\ud and emissions of non-methane volatile organic compounds\ud from vegetation. We find that their net effect was negligible(with and without an OH recycling mechanism), implyingthe change in [CH4] was almost entirely source driven―a conclusion that, though subject to significant uncertainties,can be reconciled with recent methane source estimates.\u

Topics: Atmospheric Sciences, Chemistry
Publisher: American Geophysical Union
Year: 2011
DOI identifier: 10.1029/2011GL049545
OAI identifier: oai:nora.nerc.ac.uk:16505

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