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Large Variations in Volcanic Aerosol Forcing Efficiency Due to Eruption Source Parameters and Rapid Adjustments
Author(s) -
Marshall Lauren R.,
Smith Christopher J.,
Forster Piers M.,
Aubry Thomas J.,
Andrews Timothy,
Schmidt Anja
Publication year - 2020
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 - 10.1029/2020gl090241
Subject(s) - volcano , radiative forcing , atmospheric sciences , forcing (mathematics) , vulcanian eruption , aerosol , environmental science , climatology , climate model , sulfate aerosol , cloud forcing , radiative transfer , middle latitudes , geology , climate change , meteorology , stratosphere , physics , oceanography , quantum mechanics , seismology
Abstract The relationship between volcanic stratospheric aerosol optical depth (SAOD) and volcanic radiative forcing is key for quantifying volcanic climate impacts. In their Fifth Assessment Report, the Intergovernmental Panel on Climate Change used one scaling factor between volcanic SAOD and volcanic forcing based on climate model simulations of the 1991 Mt. Pinatubo eruption, which may not be appropriate for all eruptions. Using a large ensemble of aerosol‐chemistry‐climate simulations of eruptions with different sulfur dioxide emissions, latitudes, emission altitudes, and seasons, we find that the effective radiative forcing (ERF) is on average 20% less than the instantaneous radiative forcing, predominantly due to a positive shortwave cloud adjustment. In our model, the volcanic SAOD‐ERF relationship is non‐unique and varies widely depending on time since an eruption, eruption latitude, and season due to differences in aerosol dispersion and incoming solar radiation. Our revised SAOD‐ERF relationships suggest that volcanic forcing has been previously overestimated.