The sulphate aerosol (direct effect) and greenhouse gas experiment (GSD): The forcing includes not only the greenhouse gas forcing described with the "greenhouse run" but also the direct radiative effect of historic sulphate aerosol concentrations from 1860 to 1990 and a scenario of sulphate aerosol concentrations from 1990 to 2049. The sulphate aerosol concentrations are calculated in the ECHAM4 model from the sulphur emissions in the IS92a scenario. The climatology constructed from this 240-year CTL run serves as a reference for the time-dependent forcing experiments GHG, GSD and GSDIO (EH4OPYC_22670GHG_,EH4OPYC_22697GSD_, EH4OPYC_22723GSDIO_). These data represent monthly averaged surface values of selected variables for the IPCC-Data Distribution Centre. (see also http://www.ipcc-data.org/ )