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Reconciling the changes in atmospheric methane sources and sinks between the Last Glacial Maximum and the pre‐industrial era
Author(s) -
Levine J. G.,
Wolff E. W.,
Jones A. E.,
Sime L. C.,
Valdes P. J.,
Archibald A. T.,
Carver G. D.,
Warwick N. J.,
Pyle J. A.
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl049545
Subject(s) - atmospheric methane , methane , environmental science , atmospheric sciences , glacial period , earth science , climatology , geology , chemistry , geomorphology , organic chemistry
We know from the ice record that the concentration of atmospheric methane, [CH 4 ], at the Last Glacial Maximum (LGM) was roughly half that in the pre‐industrial era (PI), but how much of the difference was source‐driven, and how much was sink‐driven, remains uncertain. Recent developments include: a higher estimate of the LGM‐PI change in methane emissions from wetlands―the dominant, natural methane source; and the possible recycling of OH consumed in isoprene oxidation―the principal methane sink. Here, in view of these developments, we use an atmospheric chemistry‐transport model to re‐examine the main factors affecting OH during this period: changes in air temperature and emissions of non‐methane volatile organic compounds from vegetation. We find that their net effect was negligible (with and without an OH recycling mechanism), implying the change in [CH 4 ] was almost entirely source driven―a conclusion that, though subject to significant uncertainties, can be reconciled with recent methane source estimates.