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 Pre-industrial control experiment (picntrl). _ This simulation was initiated from year 0084-09 of PCM1 model run G05.02 and executed on hardware ute.ucar.edu. The input external forcings are ozone forcing : noaao3.1870.093098.nc, cycled solar forcing : Fixed 1367.0 W m-2 GHGs : Fixed 1870 values; defined in code, see website volcanic forcing : none SOx emissions : sulfate_1985ab.nc, scaled to 1870 values in code Physical constants used for derived data: Lv (latent heat of evaporation): 2.501e6 J kg-1 Lf (latent heat of fusion ): 3.337e5 J kg-1 r[h2o] (density of water ): 1000 kg m-3 _ 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/.