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 committed climate change experiment (COMMIT). These datasets are available in netCDF and GRIB format. For this experiment there are 4 ensemble runs available. Spinup: restart files from end of experiment 20C3M (corresponding realisation). Anthropogenic (GHGs, sulfate aerosol direct and first indirect effects) and natural forcing (solar irradiance and volcanic activity implemented through varying solar constant) are used for the 20C3Msimulations. Model output data for CMIP3 in higher temporal resolutions and further variables are available in ESGF at https://esgf-node.llnl.gov/search/cmip3/.