Science update: GeoMIP (Geoengineering Model Intercomparison Project) climate model response

A recent JGR article by B. Kravitz and co-authors presents results from one of the GeoMIP model experiments (experiment G1). This experiment looks at the climate response of 12 models to an abrupt quadrupling of CO2 from preindustrial concentrations brought into radiative balance via a globally uniform reduction in insolation. The model results indicate that this reduction offsets global mean surface temperature to a large extent and also prevents 97% of Arctic sea-ice loss. However, compared to the preindustrial climate, the tropics are cooler (-0.3K) while the poles are warmer (+0.8K). Annual mean precipitation minus evaporation anomalies remain largely unchanged, except over some tropical regions where precipitation is slightly reduced. Global average net primary production increases by 120% above simulated preindustrial levels, mainly because of CO2 fertilisation, but also because of reduced plant heat stress compared to a world without geoengineering. Importantly, however, all models show that uniform solar geoengineering in the G1 experiment cannot simultaneously return regional and global temperature and hydrologic cycle intensity to preindustrial levels. The full abstract can be found here.