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Uncertainty in the magnitude of aerosol‐cloud radiative forcing over recent decades
Author(s) -
Regayre L. A.,
Pringle K. J.,
Booth B. B. B.,
Lee L. A.,
Mann G. W.,
Browse J.,
Woodhouse M. T.,
Rap A.,
Reddington C. L.,
Carslaw K. S.
Publication year - 2014
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 - 10.1002/2014gl062029
Subject(s) - radiative forcing , forcing (mathematics) , aerosol , albedo (alchemy) , cloud albedo , environmental science , cloud forcing , atmospheric sciences , climatology , climate model , earth's energy budget , climate change , climate sensitivity , radiative transfer , cloud feedback , cloud cover , meteorology , cloud computing , physics , geology , radiation , performance art , art , oceanography , computer science , operating system , quantum mechanics , art history
Aerosols and their effect on the radiative properties of clouds are one of the largest sources of uncertainty in calculations of the Earth's energy budget. Here the sensitivity of aerosol‐cloud albedo effect forcing to 31 aerosol parameters is quantified. Sensitivities are compared over three periods; 1850–2008, 1978–2008, and 1998–2008. Despite declining global anthropogenic SO 2 emissions during 1978–2008, a cancelation of regional positive and negative forcings leads to a near‐zero global mean cloud albedo effect forcing. In contrast to existing negative estimates, our results suggest that the aerosol‐cloud albedo effect was likely positive (0.006 to 0.028Wm −2 ) in the recent decade, making it harder to explain the temperature hiatus as a forced response. Proportional contributions to forcing variance from aerosol processes and natural and anthropogenic emissions are found to be period dependent. To better constrain forcing estimates, the processes that dominate uncertainty on the timescale of interest must be better understood.