Climate response to volcanic forcing: Validation of climate sensitivity of a coupled atmosphere‐ocean general circulation model

Abstract

Two versions of a coupled atmosphere‐ocean general circulation model (GCM) with different climate sensitivities are tested on global cooling following the Pinatubo volcanic eruption to investigate the validity of high climate sensitivities. The higher‐sensitivity version, with climate sensitivity of 6.3 K for doubled CO2 forcing, overestimates cooling due to the volcanic eruption, whereas the lower‐sensitivity version (4.0 K) produces results consistent with observations. A simple scheme for climate feedback analysis is devised and it is found that the difference between the two versions is attributed to cloud‐albedo feedback. This validation method is expected to provide additional constraints on climate sensitivity and possibly lead to reduced uncertainties in climate prediction.