BeschreibungKomponenten des Strahlungsantriebs.svg |
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Understanding global warming requires understanding the changes in climate forcings that have occurred since the industrial revolution. These include positive forcing from increased greenhouse gases negative forcing from increased sulphate aerosols and poorly constrained forcings from indirect areosol feedbacks as well as minor contributions from solar variability and other factors. The poorly constrained aerosol effects results from both limited physical undersanding of how aerosols interact with the atmosphere and limited knowledge of aerosol concentrations during the pre-industrial period. This is a significant source of uncertainty in comparing modern climate forcings to past states.
Contrary to the impression given by this figure, it is not possible to simply sum the radiative forcing contributions from all sources and obtain a total forcing. This is because different forcing terms can interact to either amplify or interfere with each other. For example, in the case of greenhouse gases, two different gases may share the same absorption bands thus partially limiting their effectiveness when taken in combination.
Der Strahlungsantrieb der einzelnen Faktoren wird in der technischen Zusammenfassung des Vierten IPCC-Sachstandsbericht der Arbeitsgruppe I folgendermaßen angegeben (jeweils in Watt pro Quadratmeter):
- CO2: 1,66 (1,49-1,83)
- CH4: 0,48 (0,43-0,53)
- N2O: 0,16 (0,14-0,18)
- FCKW/FKW: 0,34 (0,31-0,37)
- Stratosphärisches Ozon: -0,05 (-0,15-0,05)
- Troposphärisches Ozon: 0,35 (0,25-0,65)
- Stratosphärischer Wasserdampf von CH4: 0,07 (0,02-0,12)
- Oberflächenalbedo durch Landnutzung: -0,2 (-0,4-0,0)
- Oberflächenalbedo durch Ruß auf Schnee: 0,1 (0,0-0,2)
- Direkter Aerosoleffekt: -0,5 (-0,9--0,1)
- Wolken-Albedo-Effekt: -0,7 (-1,8--0,3)
- Luftfahrt-Kondensstreifen: 0,01 (0,003-0,03)
- Solarstrahlung: 0,12 (0,06-0,30)
- Nettoeffekt anthropogen: 1,6 (0,6-2,4)
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