The dependence of equilibrium climate sensitivity on climate state: Applications to studies of climates colder than present

Abstract We investigate the sensitivity of climate to a broad range of greenhouse gas forcing with coupled atmosphere‐ocean general circulation models using atmospheric CO2 concentrations ranging from ~1400 to ~200 ppm. We show that climate sensitivity is greater when the base state climate is colder, a result noted previously but with models of much lower resolution and different parameterizations. The enhanced cold state sensitivity is more apparent in models coupled to dynamical versus slab oceans. The disproportionately large sensitivity for cold climates has applications to studies of climates colder than present.