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| Titel |
Attribution of recent trends in atmospheric methane using inverse modelling |
| VerfasserIn |
Joe McNorton, Chris Wilson, Manuel Gloor, Martyn Chipperfield |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149345
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| Publikation (Nr.) |
 EGU/EGU2017-13680.pdf |
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| Zusammenfassung |
| Atmospheric methane (CH4) accounts for approximately 20% of the total direct
anthropogenic radiative forcing by long-lived greenhouse gases (0.48±0.05 Wm−2), the
second largest contributor after CO2. Atmospheric observations highlight two notable
changes in CH4 since 2007. Firstly, the growth rate of methane increased to ∼7ppb/yr.
Secondly, the CH4 13C/12C-ratio (δ13C) has become increasingly 13C-depleted. One
possible explanation for both of these, is an increase in 13C-depleted CH4 emissions. This
could be through increases in natural biogenic sources (e.g. wetlands), anthropogenic
biogenic sources (e.g. agriculture) or a combination of both. A decrease in 13C-enriched
non-biogenic emissions (e.g. biomass burning) could be an explanation for the 13C-depletion,
but does not explain the CH4 increase. A reduction in the atmospheric concentration of OH,
the main oxidant for atmospheric methane, could also explain both 13C-depletion and CH4
increase.
We have performed a synthesis inversion using a 3-D atmospheric global chemical
transport model, TOMCAT, for both CH4 and δ13C from 2005-2014. The inversion uses
surface observations of both CH4 and δ13C to spatially constrain source types and possible
changes to OH concentration. We will use results from this synthesis inversion to attribute the
upturn in CH4 growth to specific source and sinks, and to discuss the uncertainties in this
attribution. |
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