Climate model response from the Geoengineering Model Intercomparison Project (GeoMIP)

We present results from Experiment G1 of the Geoengineering Model Intercomparison Project, in which 12 climate models have simulated the climate response to an abrupt quadrupling of CO₂ from preindustrial concentrations brought into radiative balance via a globally uniform reduction in insolation.

Models show this reduction largely offsets global mean surface temperature increases due to quadrupled CO₂ concentrations and prevents 97% of the Arctic sea ice loss that would otherwise occur under high CO₂ levels but, compared to the preindustrial climate, leaves the tropics cooler (-0.3 K) and the poles warmer (+0.8 K). Annual mean precipitation minus evaporation anomalies for G1 are less than 0.2 mm day⁻¹ in magnitude over 92% of the globe, but some tropical regions receive less precipitation, in part due to increased moist static stability and suppression of convection.