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Methane CH4

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fig. 3-1

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Northern hemispheric CO2 distribution as observed by SCIAMACHY. The differences between spring and summer are due to the CO2 'breathing' of the vegetation. (Graphics: M. Buchwitz, IUP-IFE, University of Bremen)
 

SCIAMACHY nadir observations in the SWIR spectral region formed the basis for the retrieved CO2 information (Buchwitz et al. 2005a, 2007a, Bösch et al. 2006, Barkley et al. 2007, Reuter et al. 2010, Schneising et al. 2008). The CO2 mixing ratio is obtained by normalising the CO2 column with the simultaneously retrieved airmass from oxygen measurements (Schneising et al. 2008) or by using meteorological surface pressure (Barkley et al. 2007). (fig. 3-1)

Methane – CH4

CH4 is the second most important anthropogenic greenhouse gas next to CO2. It is regulated by the Kyoto Protocol, as well. Compared to pre-industrial times, CH4 concentrations have more than doubled due to anthropogenic activities. Although the total sum of all CH4 sources, about 550 Tg/year, is relatively well known, the distribution among different source categories is highly uncertain and impedes our capability to reliably predict CH4 source strengths in a warming climate. First results from SCIAMACHY showed substantially higher tropical CH4 abundances than previously estimated (Frankenberg et al. 2005). Even though these results were recently partially revised (Frankenberg et al. 2008), the fact that tropical emissions are very high, constituting about a third of all CH4 emissions, remains true. In general, SCIAMACHY CH4 retrievals have substantially matured and results from several independent studies (see also Buchwitz et al. 2005b, Schneising et al. 2009) draw a consistent picture of the global distribution of this greenhouse gas.

 

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fig. 3-2

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Methane emission derived from SCIAMACHY data. Left column: Column-averaged CH4 mixing ratios (XCH4) over South-East Asia from SCIAMACHY for summer and autumn 2004. Right column: Modelled emissions per 1? ? 1? grid cell. (Graphics: adapted from Bergamaschi et al. 2009, reproduced by permission of American Geophysical Union)
 

 

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