Stratospheric Aerosol Climate Intervention Designed to Minimize Negative Impacts

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Increasing greenhouse gases (GHGs) can strongly affect the climate system and potentially our future survival. The obvious, but difficult, solution lies in drastically curbing GHG emissions. Failing that, a way to offset the expected global warming induced by GHGs may be geoengineering. A strategy in geoengineering involves the "injection" of sulphate aerosols into the stratosphere to reflect sunlight. Mimicking what naturally occurs during volcanic eruptions, this strategy can mitigate global warming. However, it may also produce unintended consequences like reduced globally averaged precipitation and enhanced ultraviolet (UV) radiation and ozone concentration near the surface. These consequences can impact agriculture, altering food production. This project aims to understand the uncertainties of sulphate aerosol injection and evaluate its impacts on agriculture. Understanding these impacts is essential if geoengineering is indeed needed. The principal investigators (PIs) of this project will conduct numerical experiments of injecting aerosols into the stratosphere using the Whole Atmosphere Community Climate Model of the NCAR Community Earth System Model (CESM2). The PIs will then explore ways to introduce the injection to reduce global warming while minimizing impacts on agriculture that result from stratospheric ozone depletion due to sulfate aerosols. CESM2 includes complete treatment of diffuse radiation, aerosols, and atmospheric chemistry, as well as built in simulations of crop production. The PIs will update the crop model to include sensitivity to UV and to better represent ozone damage, which will allow more accurate representation of crop impacts. The work will support the Geoengineering Model Intercomparison Project (GeoMIP) as part of the Coupled Model Intercomparison Project 6 (CMIP6).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.