Soil moisture and other hydrological changes in a stratospheric aerosol geoengineering large ensemble

Here we investigate the impact of stratospheric aerosol geoengineering on the terrestrial hydrological cycle. We use the Geoengineering Large Ensemble, which involves a 20-member ensemble of simulations using the Community Earth System Model with the Whole Atmosphere Community Climate Model, in which sulfur dioxide (SO2) was injected into the stratosphere at four different locations, to maintain global mean surface temperature, and also the interhemispheric and equator-to-pole temperature gradients at values representative of 2020 ("baseline") under the Representative Concentration Pathway 8.5.

In our simulations, annual mean land precipitation and evapotranspiration (ET) increase by 12% each under Representative Concentration Pathway 8.5. Under the Geoengineering Large Ensemble, the hydrological cycle is suppressed compared to the baseline, with end-of-century decreases of 1.4% (12 +/- 5 mm/year) and 3.3% (18 +/- 2 mm/year) in global mean, annual mean precipitation, and ET over land, respectively. Geoengineering effectively maintains global mean soil moisture under a high CO2 scenario, although there is significant regional variability.