Simulation of the climate effects of a geoengineered stratospheric sulfate cloud with the NASA GEOSCCM

Suggested solar radiation management (SRM) methods to mitigate global warming include the injection of sulfur dioxide (SO₂ ) in the stratosphere. We present the results from SRM simulation ensemble performed with the NASA GEOS-5 Chemistry Climate Model (GEOSCCM). We focus on the response of the stratosphere to a stratospheric SO₂ injection. In particular, we investigate the changes of the stratospheric dynamics and composition, and the impact of an increased aerosol layer on ozone recovery. As prescribed for experiment G4 of the Geoengineering Model Intercomparison Project (GeoMIP), we inject 5 Tg/year of SO₂ from 2020 to 2070. The location of the injection is the equator at 0° longitude between 16 km and 25 km altitude. After 2070, we interrupt the SO₂ injection and simulate the readjustment until 2090. The emissions scenario is RCP4.5, which predicts a radiative forcing of about 4.5 W/m² by 2100. This is considered a "medium-low" scenario in terms of radiative forcing. GEOSCCM does not include an interactive ocean model, therefore we use the sea surface temperatures forecasted by the Community Climate System Model Version 4 (CCSM4) for RCP4.5.