An Overview of Geoengineering of Climate using Stratospheric Sulfate Aerosols

1 We provide an overview of geoengineering by stratospheric sulfate aerosols. We review the state of understanding 2 about this topic as of early 2008, summarizing the past 30 years of work in the area, and highlight some very recent 3 studies using general circulation models of the atmosphere and ocean, and discuss the efficacy of producing such 4 aerosols by methods used to deliver sulfur species to the stratosphere. 5 The studies reviewed here all suggest that sulfate aerosols can counteract the globally averaged temperature 6 increase associated with increasing greenhouse gases, and reduce changes to some other components of the earth 7 system. There are likely to be remaining regional climate changes after geoengineering, with some regions expe8 riencing significant changes in temperature or precipitation. The aerosols also serve as surfaces for heterogeneous 9 chemistry resulting in increased ozone depletion for several decades. We conclude by highlighting many of the 10 areas where more research is needed. 11