Global Agricultural Impacts of Stratospheric Aerosol Intervention With An Overshoot Scenario

Abstract:

Stratospheric aerosol intervention (SAI) is a suggested strategy to reduce anthropogenic global warming. If a sulfate aerosol cloud could be created in the stratosphere it would reflect sunlight, reduce solar radiation reaching the surface, and cool Earth. However, there are many potential side effects of SAI, and agricultural impacts are an important one. Previous studies show that cooling from SAI would benefit regional agricultural productivity in general, but agricultural impacts are uncertain when all climate changes from SAI are considered. We worked with the Global Gridded Crop Model Intercomparison project to have a comprehensive assessment using a SAI scenario proposed by the Geoengineering Model Intercomparison Project. This overshoot scenario uses SSP5-3.4-OS as the reference case, which assumes that mitigation and carbon removal strategies would start on a SSP5-8.5 pathway in 2040 to reach the radiative forcing target of 3.4 W/m² higher than pre-industrial by 2100. However there will be decades with global temperature higher 1.5 or 2°C above preindustrial. In the SAI scenario, stratospheric sulfate aerosol would keep the temperature under these limits. We processed Earth system model (CESM2) output of 2-m air temperature, precipitation and solar radiation to force offline crop models, including CLM5crop, pDSSAT and LPJmL, and compare the offline simulations with coupled CLM5crop simulations with CESM2. Offline crop model simulations show that SAI would increase agricultural productivity of certain major cereal crops compared to the reference case, although regional differences are identified. We encourage more global crop modeling groups to participate in this project.