Diagnosis of climate models in terms of transient climate response and feedback response time

Abstract

Climate models have traditionally been characterised by their climate sensitivity (equilibrium response to a doubling of CO2) and their ocean heat uptake. Together these determine a third property: the transient climate response to a linear increase in radiative forcing. A fourth property, the feedback response time is introduced here and shown to provide a complementary diagnostic of climate model behaviour. In particular, it demonstrates that the discrepancy between recent climate observations and the general circulation models in the 'IPCC ensemble' primarily arises because the models are undersampling the range of transient climate responses consistent with recent attributable greenhouse warming. Copyright © 2007 Royal Meteorological Society.