The control integration, in which the atmospheric forcing is kept constant, simulates a period over 300 years in length. Control experiment (CTL): In CTL, greenhouse gases and aerosols are prescribed exactly as in the uncoupled ECHAM-4 model. The concentrations of carbon dioxide, methane and nitrous oxide are fixed at the observed 1990 values (IPCC'90, Table 2.5), the concentrations of the industrial gases (CFC's and others) are set to zero, while ozone and aerosols are prescribed as climatological distributions. There is no sulfur cycle in CTL. After a 100-year spin up the model was run, with constant flux adjustment, for another 300 years (Roeckner et al., 1998). The climatology constructed from this 300-year CTL run serves as a reference for the time-dependent forcing experiments GHG, GSD and GSDIO (EH4OPYC_22670GHG_, EH4OPYC_22697GSD_, EH4OPYC_22723GSDIO_).