Transient response of the Hadley Centre coupled ocean-atmosphere model to increasing carbon dioxide. Part III: analysis of global- mean response using simple models

Abstract

The roles of surface, atmospheric, and oceanic feedbacks in controlling the global-mean transient response of a coupled ocean-atmosphere general circulation model to increasing carbon dioxide are investigated. The land-sea contrast in the surface warming is explained almost entirely by the shortwave radiative feedbacks associated with changes in cloud and surface albedo. The oceanic thermal inertia delays the response; however, the initial delay is enhanced by increases in Antarctic sea-ice cover, which substantially reduce the effective climate sensitivity of the model in the first half of the 75-year experiment. However, inclusion of the direct forcing due to anthropogenic tropospheric sulphate aerosol eliminates the land/sea contrast in the response at 1990, leaving the simulated warming over land slightly below the observed value, although the rapid warming observed during the 1980s is well reproduced. -from Author