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 A1B experiment. For this experiment there is only one run available. Initial conditions for this experiment were taken from 1 January 2001 of the climate of the 20th century experiment named CM2.1U-D4_1860-2000-AllForc_H2. Several time varying forcing agents used during the first 100 years of this CM2.1U-H2_SresA1B_X1 experiment were based on output of the MOZART global atmospheric chemistry climate model when driven with the SRES A1B emission scenarios. For the CM2.1U-H2_SresA1B_X1 experiment volcanic aerosols were zero, land surface cover types were time invariant, and solar irradiance varied seasonally based upon late 20th century averages but with no interannual variation. All forcing agents were held constant after year 2100. For model output data in higher temporal resulution and more variables visit the web page https://esg.llnl.gov:8443/home/publicHomePage.do.