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| Titel |
Variations in global methane sources and sinks during 1910–2010 |
| VerfasserIn |
A. Ghosh, P. K. Patra, K. Ishijima, T. Umezawa, A. Ito, D. M. Etheridge, S. Sugawara, K. Kawamura, J. B. Miller, E. J. Dlugokencky, P. B. Krummel, P. J. Fraser, L. P. Steele, R. L. Langenfelds, C. M. Trudinger, J. W. C. White, B. Vaughn, T. Saeki, S. Aoki, T. Nakazawa |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 5 ; Nr. 15, no. 5 (2015-03-09), S.2595-2612 |
| Datensatznummer |
250119504
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| Publikation (Nr.) |
 copernicus.org/acp-15-2595-2015.pdf |
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| Zusammenfassung |
| Atmospheric methane (CH4) increased from ~900 ppb (parts per
billion, or nanomoles per mole of dry air) in 1900 to ~1800 ppb in 2010
at a rate unprecedented in any observational records. However, the
contributions of the various methane sources and sinks to the CH4 increase
are poorly understood. Here we use initial emissions from bottom-up
inventories for anthropogenic sources, emissions from wetlands and rice
paddies simulated by a~terrestrial biogeochemical model, and an atmospheric
general circulation model (AGCM)-based chemistry-transport model (i.e. ACTM)
to simulate atmospheric CH4 concentrations for 1910–2010. The ACTM
simulations are compared with the CH4 concentration records reconstructed
from Antarctic and Arctic ice cores and firn air samples, and from direct
measurements since the 1980s at multiple sites around the globe. The
differences between ACTM simulations and observed CH4 concentrations are
minimized to optimize the global total emissions using a mass balance
calculation. During 1910–2010, the global total CH4 emission doubled from
~290 to ~580 Tg yr−1. Compared to optimized emission, the
bottom-up emission data set underestimates the rate of change of global total
CH4 emissions by ~30% during the high growth period of
1940–1990, while it overestimates by ~380% during the low growth
period of 1990–2010. Further, using the CH4 stable carbon isotopic data
(δ13C), we attribute the emission increase during 1940–1990
primarily to enhancement of biomass burning. The total lifetime of CH4
shortened from 9.4 yr during 1910–1919 to 9 yr during 2000–2009 by the
combined effect of the increasing abundance of atomic chlorine radicals (Cl) and
increases in average air temperature. We show that changes of CH4 loss
rate due to increased tropospheric air temperature and CH4 loss due to Cl
in the stratosphere are important sources of uncertainty to more accurately
estimate the global CH4 budget from δ13C observations. |
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