Forcing Dependence of Atmospheric Lapse Rate Changes Dominates Residual Polar Warming in Solar Radiation Management Climate Scenarios

Abstract

Simulations of solar radiation management (SRM) geoengineering using comprehensive general circulation models show a residual surface warming at high latitudes. Previous work attributes this to the difference in forcing structure between the increase in greenhouse gases and decrease in insolation, but this neglects the role of the induced reduction in atmospheric energy transport. Here we show that the difference in vertical structure of temperature change between increasing CO2, decreasing insolation, and decreasing atmospheric energy transport is the dominant reason for the residual near-surface warming at high latitudes. A single-column model (SCM) is used to decompose the high-latitude temperature change and shows the importance of the enhanced near-surface warming from the CO2 increase in explaining the residual polar warming. This suite of models invites caution when attributing high-latitude surface temperature changes to the lapse rate feedback, as various forcings and nonlocal processes affect the vertical structure of temperature change differently.