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. SRES B1 experiment with CSIRO Mk 3.0 model, starting from year 1939 (model year 189) of 20C3M expierment. Radiative forcings held constant from year 2100. For this experiment there is only one run available. For model output data in higher temporal resulution and more variables visit the web page https://esg.llnl.gov:8443/home/publicHomePage.do.