The ability of stratospheric sulfate aerosols to create a global dimming effect has made them a possible candidate for use in climate engineering projects[1] to limit the effect and impact of climate change due to rising levels of greenhouse gases.[2] Delivery of precursor sulfide gases such as sulfuric acid,[3] hydrogen sulfide (H2S) or sulfur dioxide (SO2) by artillery, aircraft[4] and balloons has been proposed.[5]
Tom Wigley calculated the impact of injecting sulfate particles, or aerosols, every one to four years into the stratosphere in amounts equal to those lofted by the volcanic eruption of Mount Pinatubo in 1991,[6] but did not address the many technical and political challenges involved in potential climate engineering efforts.[7] If found to be economically, environmentally and technologically viable, such injections could provide a "grace period" of up to 20 years before major cutbacks in greenhouse gas emissions would be required, he concludes.
Direct delivery of precursors is proposed by Paul Crutzen.[4] This would typically be achieved using sulfide gases such as dimethyl sulfide, sulfur dioxide (SO2), carbonyl sulfide, or hydrogen sulfide (H2S).[5] These compounds would be delivered using artillery, aircraft (such as the high-flying F-15C)[4] or balloons, and result in the formation of compounds with the sulfate anion SO42-.[5]
According to estimates by the Council on Foreign Relations, "one kilogram of well placed sulfur in the stratosphere would roughly offset the warming effect of several hundred thousand kilograms of carbon dioxide."[8]
