The radiative effect of the anthropogenic influence on the stratospheric sulfate aerosol layer

Stratospheric sulfate aerosols have a cooling effect on the Earth’s surface. Sulfur aerosols from large volcanic eruptions are often the dominant source, while non-volcanic background stratospheric sulfate aerosols are supposed to mainly originate from carbonyl sulfide (OCS). Several recent studies indicate, however, that this latter source is too small to account for the observed background stratospheric aerosol concentration. Based on model calculations we suggest that most of the lower stratospheric sulfate aerosol concentration is of anthropogenic origin. We estimate a global mean radiative forcing due to the anthropogenic influence on the stratospheric aerosol layer of −0.05 Wm⁻². This represents a new climate forcing mechanism and emphasizes anthropogenic sulfur emission as an important cooling mechanism.