These data represent monthly averaged values of selected variables for the Data Distribution Centre (DDC) of the Intergovernmental Panel on Climate Change (IPCC). (see also http://www.ipcc-data.org/) The model output prepared for IPCC Fourth Assessment SRES B1 experiment. These datasets are available in netCDF and GRIB format. The dataset names are composed of - centre/model acronym (e.g. MPEH5: Max-Planck-Institute/Echam5) - scenario acronym (e.g. SRB1: SRES B1) - run number (e.g. 1: run 1) - format identifier (e.g. N: netCDF, G: GRIB) - variable acronym [with level value] (e.g. hur850: relative humidity, 850 hPa) --> example: MPEH5_SRB1_1_G_hur850 This model run continues from the end of the 20th century simulation with GHG and aerosol loadings for the IPCC SRES B1 scenario as tabulated in the IPCC Third Assessment Report, Appendix II. The CO2 concentrations are from the Bern-CC model (Contribution of Working Group I to the Third Assesment Report of IPCC, p808) and the aerosol loadings are from O. Boucher, Laboratoire d\'Optique Atmospherique, France. For years 2101-2300, all GHG concentrations and the aerosol loading are held constant at the values obtained by extrapolation to year 2101. For this experiment there are 4 ensemble runs available. Model output data for CMIP3 in higher temporal resolutions and further variables are available in ESGF at https://esgf-node.llnl.gov/search/cmip3/.