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 is only one run available. The initial condition is taken from the end of the 20C3M run. This experiment simulates committed climate change by forcing in the past, assuming all the anthropogenic forcing is fixed at year 2000 levels. Model output data for CMIP3 in higher temporal resolutions and further variables are available in ESGF at https://esgf-node.llnl.gov/search/cmip3/.