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 https://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 1 ensemble run available. Experiment was initiated from nominal year 1999 of the 20C3M part of simulation XX1. Forcing agents were held fixed at year 2000 values throughout the experiment. Forcing agents included: CO2,CH4,N2O,O3,CFC11(including other CFCs and HFCs), CFC12; sulfate(Boucher),BC,sea salt,desert dust aerosols. Model output data for CMIP3 in higher temporal resolutions and further variables are available in ESGF at https://esgf-node.llnl.gov/search/cmip3/.