The atmosphere-ocean general circulation model ECHAM3/LSG is used for climate change and climate variability studies. The control integration, in which the atmospheric forcing is kept constant, simulates a period over several 100 years in length. In order to study the internal variability of the model a control simulation with fixed present-day CO2 concentration has been performed.. The models ECHAM3 and LSG are described in the DKRZ reports No.6 and No.2, respectively. These data represent monthly averaged surface values of selected variables for the IPCC-Data Distribution Centre. (see also http://www.ipcc-data.org/ )