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The ability of stratospheric sulfate aerosols to create a global dimming effect has made them a possible candidate for use in solar radiation management climate engineering projects to limit the effect and impact of climate change due to rising levels of greenhouse gases.〔 Delivery of precursor sulfide gases such as sulfuric acid, hydrogen sulfide (H2S) or sulfur dioxide (SO2) by artillery, aircraft and balloons has been proposed. 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, but did not address the many technical and political challenges involved in potential solar radiation management efforts. 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. It has been suggested that the direct delivery of precursors could be achieved using sulfide gases such as dimethyl sulfide, sulfur dioxide (SO2), carbonyl sulfide, or hydrogen sulfide (H2S).〔 These compounds would be delivered using artillery, aircraft (such as the high-flying F-15C)〔 or balloons, and result in the formation of compounds with the sulfate anion SO42−.〔 According to estimates, "one kilogram of well placed sulfur in the stratosphere would roughly offset the warming effect of several hundred thousand kilograms of carbon dioxide." ==Arguments for the technique== The arguments in favour of this approach in comparison to other possible means of solar radiation management are: * Mimics a natural process: Stratospheric sulfur aerosols are created by existing natural processes (especially volcanoes), whose impacts have been studied via observations. This contrasts with other, more speculative solar radiation management techniques which do not have natural analogs (e.g., space sunshade). * Technological feasibility: In contrast to other proposed solar radiation management techniques, such as marine cloud brightening and space sunshades, much of the required technology is pre-existing: chemical manufacturing, artillery shells, high-altitude aircraft, weather balloons, etc.〔 * Cost: The low-tech nature of this approach has led commentators to suggest it would cost less than many other interventions. Costs cannot be derived in a wholly objective fashion, as pricing can only be roughly estimated at an early stage. However, many sources suggest that it would be cheap relative to cutting emissions. According to Paul Crutzen, the annual cost of enough stratospheric sulfur injections to counteract effects of doubling CO2 concentrations from 280 to 560 ppm would be $25–50 billion a year.〔 This is over 100 times cheaper than preventing the temperature change caused by this additional 280 ppm CO2 via reducing greenhouse gas emissions. * Efficacy: Most proposed solar radiation management techniques can only provide a limited intervention in the climate—one cannot reduce the temperature by more than a certain amount with each technique. New research by Lenton and Vaughan suggests that this technique may have a high radiative 'forcing potential'. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Stratospheric sulfate aerosols (geoengineering)」の詳細全文を読む スポンサード リンク
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