Collaborative Research: Evaluation of Suggestions to Geoengineer the Climate System Using Stratospheric Aerosols and Sun Shading

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"Geoengineering" is the idea of taking purposeful action to mitigate the effects of inadvertent global greenhouse warming. While a number of schemes have been proposed, the most plausible involve reducing the intensity of solar radiation reaching Earth's surface, either by injecting particles into the stratosphere or by stationing reflectors between the Earth and the Sun in space at the first Lagrange point (L1).This program of modeling studies will address how such injected aerosols would behave and how the solar shading would affect the climate. In addition, the policy and ethical considerations of these geoengineering schemes will be analyzed.Plausible scenarios for geoengineered aerosol injections and L1 sun-shading will be generated. Modules will be developed to calculate the detailed evolution of the injected aerosols in climate models. Global circulation models will then be run using these scenarios and modules. These experiments will address a wide range of questions about geoengineering, including the possible increase in acidic precipitation from the injection of sulfate aerosol, the increase in diffuse and decrease in direct solar radiation, regional climate changes, the potential for rapid severe warming if or when the aerosol injection ceases, interactions between the effects of natural volcanic and geoengineered aerosols, effects on cirrus clouds, interactions with natural climate variations such as El Nino, and contributions to tropospheric burdens of pollutants.The experiments will involve the introduction of detailed aerosol evolution schemes into two climate models, the Goddard Space Flight Center GEOS5 model, which features high spatial resolution, and the Goddard Institute for Space Studies (GISS) ModelE, which has lower resolution and will be used for exploratory experiments. Co-investigator Bunzl, from Rutger's Department of Philosophy, will serve as a bridge between the climate modeling work and social scientists, who will be invited to study the model results and use them in social-science models. The potential risks and benefits of geoengineering will be analyzed and the extent to which these are distributed unevenly across communities and regions will be considered.The broader impacts of this project stem from the need for studies, such as this, to inform policy makers and the public regarding the potential costs and benefits of different geoengineering schemes.