In recent years, the idea of geoengineering, artificially modifying the climate to reduce global temperatures, has received increasing attention because of the lack of progress in reducing global greenhouse gas emissions. Stratospheric sulfate injection (SSI) is a geoengineering method proposed to reduce planetary warming by reflecting a proportion of solar radiation back into space that would otherwise warm the surface and lower atmosphere. The authors analyze results from the Met Office Hadley Centre Global Environment Model, version 2, Carbon Cycle Stratosphere (HadGEM2-CCS) climate model with stratospheric emissions of 10 Tg yr−1 of SO2, designed to offset global temperature rise by around 1°C. A reduction in concentrating solar power output of 5.9% on average over land is shown under SSI relative to a baseline future climate change scenario (RCP4.5) caused by a decrease in direct radiation. Solar photovoltaic energy is generally less affected as it can use diffuse radiation, which increases under SSI, at the expense of direct radiation. The results from HadGEM2-CCS are compared with the Goddard Earth Observing System Chemistry–Climate Model (GEOSCCM) from the Geoengineering Model Intercomparison Project (GeoMIP), with 5 Tg yr−1 emission of SO2. In many regions, the differences predicted in solar energy output between the SSI and RCP4.5 simulations are robust, as the sign of the changes for both HadGEM2-CCS and GEOSCCM agree. Furthermore, the sign of the total and direct annual mean radiation changes evaluated by HadGEM2-CCS agrees with the sign of the multimodel mean changes of an ensemble of GeoMIP models over the majority of the world.
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Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/JAMC-D-16-0298.s1.
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