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Sulphates, Climate and Coal

AUTHOR: Deborah M.B. Adams, Irene Smith
DATE: January 1995

The latest in the series of Perspectives reports from IEA Coal Research reviews SO2 emissions from coal, the formation of sulphates and their role in the climate.

Coal combustion is estimated to be the source of about 60% of SO2 emissions from human activities, and 35-77% of total SO2 emissions, including natural emissions. Over 80% of emissions from human activities originate in the Northern Hemisphere. SO2 is short lived in the atmosphere. It forms sulphates, mainly by reaction in the queous-phase with H2O2 or O3, or by reaction with the OH radical in the gas-phase. Sulphate aerosols have a cooling effect on the climate in two ways, directly by backscattering solar radiation or indirectly by modifying cloud structure. The effects are difficult to quantify reliably but need to be included in model simulations of climatic change. Over the long term, sulphate cooling combined with warming due to the enhanced greenhouse effect from other trace gases would result in a warming.