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| Titel |
Interpreting methane variations in the past two decades using measurements of CH4 mixing ratio and isotopic composition |
| VerfasserIn |
G. Monteil, S. Houweling, E. J. Dlugockenky, G. Maenhout, B. H. Vaughn, J. W. C. White, T. Röckmann |
| 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 ; 11, no. 17 ; Nr. 11, no. 17 (2011-09-06), S.9141-9153 |
| Datensatznummer |
250010056
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| Publikation (Nr.) |
 copernicus.org/acp-11-9141-2011.pdf |
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| Zusammenfassung |
| The availability δ13C-CH4 measurements from atmospheric samples
has significantly improved in recent years, which allows the construction of
time series spanning up to about 2 decades. We have used these measurements
to investigate the cause of the methane growth rate decline since 1980, with
a special focus on the period 1998–2006 when the methane growth came to a
halt. The constraints provided by the CH4 and δ13C-CH4
measurements are used to construct hypothetical source and sink scenarios,
which are translated into corresponding atmospheric concentrations using the
atmospheric transport model TM3 for evaluation against the measurements. The
base scenario, composed of anthropogenic emissions according to EDGAR 4.0,
constant emissions from natural sources, and a constant atmospheric lifetime,
overestimates the observed global growth rates of CH4 and
δ13C-CH4 by, respectively, 10 ppb yr−1
and 0.02‰ yr−1 after
the year 2000. It proves difficult to repair this inconsistency by modifying
trends in emissions only, notably because a temporary reduction of
isotopically light sources, such as natural wetlands, leads to a further
increase of δ13C-CH4. Furthermore, our results are difficult to
reconcile with the estimated increase of 5 Tg CH4 yr−1 in emissions from fossil
fuel use in the period 2000–2005. On the other hand, we find that a moderate
(less than 5% per decade) increase in the global OH concentration can bring
the model in agreement with the measurements for plausible emission
scenarios. This study demonstrates the value of global monitoring of methane
isotopes, and calls for further investigation into the role OH and
anthropogenic emissions to further improve our understanding of methane
variations in recent years. |
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