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 A1B experiment. These datasets are available in netCDF and GRIB format. Experiment was initiated from model year 235 (nominal year 2000)of the climate of the 20th Century experiment (with bcm_experiment_name: PT3). Varying forcing agents: CO2,CH4,N2O,CFC11(including other CFCs and HFCs),CFC12 and sulfate aerosols (Boucher data, only direct effect). Non-varying forcing agents: Background aerosols: black carbon,sea salt,desert dust, stratospheric and tropospheric ozone, solar irradiance (1368 W/m2) and the distribution of land cover types. No volcanic aerosols. No heat or fresh water adjustments. 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.