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 SRES A2 experiment. These datasets are available in netCDF and GRIB format. Started from 1989/12/1 of 20C3M (realisation 1). Includes time-varying forcing from major and minor greenhouse gases (SRES A2), plus anthropogenic sulphur cycle with direct plus indirect sulphate aerosol effects, and variations in tropospheric and stratospheric ozone based partly on off-line chemistry calculations based on SRES A2, from 1989 to 2100. Stratospheric ozone changes based on observed climatology up to the mid-1990s, with extrapolated changes persisting depletion patterns in each hemisphere scaled by effective chlorine index from the scenario. For this experiment there is only one run available. For model output data in higher temporal resulution and more variables visit the web page https://esg.llnl.gov:8443/home/publicHomePage.do.