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Parametric uncertainty effects on aerosol radiative forcing
Author(s) -
Haerter J. O.,
Roeckner E.,
Tomassini L.,
von Storch J.S.
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 - 10.1029/2009gl039050
Subject(s) - aerosol , radiative forcing , forcing (mathematics) , radiative transfer , environmental science , atmospheric sciences , climatology , cloud forcing , parametric statistics , sulfate aerosol , meteorology , range (aeronautics) , climate model , climate change , physics , mathematics , statistics , geology , materials science , composite material , oceanography , quantum mechanics
Among the known radiative forcings, the fourth IPCC assessment report estimates the aerosol radiative forcing to harbor the widest range of uncertainty extending from −1.8 to −0.3 W/m 2 . The IPCC estimates focus mainly on structural uncertainties, including uncertainties in aerosol sources. Here, we study the uncertainty of the sulfate aerosol radiative forcing due to parametric uncertainty in a state‐of‐the‐art general circulation model (GCM). Numerical experiments were carried out by perturbing seven cloud parameters in the model. We find that the uncertainty due to a single one of these parameters can be as large as 0.5 W/m 2 , and the uncertainty due to combinations of these parameters can reach more than 1 W/m 2 . These numbers should be compared with the sulfate aerosol forcing of −1.9 W/m 2 for the year 2000, obtained using the default values of the parameters. The uncertainty results from a high sensitivity of cloud optical properties to aerosol concentrations, which can be amplified by changing cloud parameter setting.