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 climate of the 1%year CO2 increase experiment (to doubling). These datasets are available in netCDF and GRIB format. This idealized scenario began from the 1850 initial condition used in all other CCCma integrations and has CO2 increasing at a rate of 1% per year from its initial value of 288ppm. The integration proceeded for 70 years (through model year 1919) at which point CO2 concentration was fixed at roughly twice its initial value (578ppm) and the integration continued for an additional 150 years (to model year 2069). For this experiment there is only one run available. Model output data for CMIP3 in higher temporal resolutions and further variables are available in ESGF at https://esgf-node.llnl.gov/search/cmip3/.