The radiative impact of a simple aerosol climatology on the Hadley Centre atmospheric GCM

Results from a new version of the Hadley Centre atmospheric general-circulation model are presented in which the sensitivity of the model to the inclusion of a simple aerosol climatology is investigated. Without aerosols, comparisons with clear-sky reflected short-wave radiation from the Earth Radiation Budget Experiment (ERBE) and the Scanner for Radiation Budget (ScaRaB) satellite measurements indicate a missing scatterer in the clear-sky atmosphere. In addition, recent estimates of global, annual mean absorbed short-wave radiation at the surface, which used the Global Energy Balance Archive (GEBA) where possible for verification, indicate that the atmosphere did not absorb enough short-wave radiation. The insertion of a simple aerosol climatology based on World Climate Research Programme recommendations into the model was found to be the only plausible means of reducing its significant short-wave bias compared with ERBE and ScaRaB measurements at the top of the atmosphere, and with GEBA data at the surface. An increase in the global, annual mean atmospheric absorbed short-wave radiation accompanied these changes.