Nonlinear Aspects of the Climate Response to Greenhouse Gas and Aerosol Forcing

Abstract

Abstract In a series of equilibrium experiments the climate response to present-day radiative forcings of anthropogenic greenhouse gases and aerosol particles is calculated. The study was performed with a model system consisting of the ECHAM4 atmospheric general circulation model coupled to a slab ocean and thermodynamic sea ice model. The model includes transport of the relevant chemical constituents, a sulfur chemistry model that calculates sulfate production in the gas and aqueous phase, and an aerosol model that accounts for source and sink processes. The aerosol cycle, the hydrological cycle, and the atmospheric dynamics are fully interactive. The climate response to aerosol forcing is not just a mirror image of the response to greenhouse forcing. This applies to the temperature changes, which are regionally more uniform for greenhouse forcing than for aerosol forcing as is already well known, and, in particular, to the hydrological cycle: the global hydrological sensitivity (Δprecip/Δtemp) to a 1-K ...