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| Titel |
A Close-up of the Methane Global Budget |
| VerfasserIn |
Stefanie Kirschke, Philippe Ciais, Philippe Bousquet, Josep Canadell, Corinne Le Quéré |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056413
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| Zusammenfassung |
| Understanding the global methane (CH4) budget, and its role in the carbon cycle, is one
important step to better understand climate change, its feedbacks and impacts on a global
scale, so as to contribute to mitigation practices and other efforts to control our changing
climate. Methane is a potent greenhouse gas and contributes 0.5 W m-2 to total
direct radiative forcing. Its short life time compared to CO2 makes it an interesting
target for emission reductions that could benefit our climate on relatively short time
scales.
Relative to our knowledge of CO2, our understanding of the global CH4 budget is limited,
and our ability to quantify its underlying drivers and its evolution is poor. The atmospheric
concentration of CH4 has increased nearly continuously and by a factor of 2.7 since
pre-industrial times mostly due to human activities. Since the beginning of atmospheric
measurements of CH4, its rate of growth has varied significantly. Large growth rates have
been observed during the late 1970s and early 1980s. Average growth rate slowed down to ca.
11 ppbv y-1 from 1983-1991, with a sharp decrease in 1992. The mid-1990s were generally
characterized by small growth rates, albeit a large increase was observed in 1998. The
atmospheric CH4 abundance was constant from 1999 through 2006, implying a steady
state in the global atmospheric CH4 budget. Near-zero growth characterized the
early 2000s, whereas from 2007-2010 growth rates increased again. Within the
Global Carbon Project (GCP), a new initiative to establish a routine update of the
CH4 global budget has been introduced. Core to the success of this initiative are
close interactions among the CH4 observational, emission inventory and modeling
communities.
Sources of CH4 – e.g. agricultural, fossil fuel use, fire, waste treatment and natural
wetland emissions – and CH4 sinks – tropospheric OH, stratospheric loss and the soil sink –
show large uncertainties and interact with the changing climate. A synthesis of the processes
controlling the CH4 budget since 1850, and a close look at the recent decades and the
variations in growth rate and CH4 source distribution and spatial gradients, will likely provide
a more detailed understanding of the CH4 global budget. Such a synthesis product will
improve our understanding of the sensitivity of natural CH4 sources to climate variability, the
largest uncertainties, the expected trends in regional fossil fuel and agricultural sources, and
provide a sound basis for understanding the behavior of CH4 in the global climate
system.
We will present the collaborative initiative, progress to date and initial results on the CH4
global budget for the last century. |
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