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 (GCM) 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 the decrease in insolation, but this neglects 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
bottom-heavy temperature change from the CO2 increase in explaining the
residual polar warming. This model hierarchy 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.