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What governs the spread in shortwave forcings in the transient IPCC AR4 models?
Author(s) -
Storelvmo T.,
Lohmann U.,
Bennartz R.
Publication year - 2009
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl036069
Subject(s) - shortwave , forcing (mathematics) , climatology , aerosol , environmental science , radiative forcing , atmospheric sciences , shortwave radiation , cloud forcing , meteorology , physics , radiative transfer , geology , quantum mechanics , radiation
The coupled global atmospheric‐ocean models used for transient simulations in the IPCC AR4 report differences in the present‐day shortwave forcing of more than 2 W/m 2 . We show here that about 1.3 W/m 2 of this spread could be explained by the different methods used to calculate cloud droplet number concentration (CDNC) from aerosol mass concentrations. Although we cannot rule out that other forcing agents could yield comparable uncertainties, this strongly points to the aerosol indirect effect as the main contributor to the wide spread in the shortwave forcing reported in IPCC AR4.