Here the greenhouse gas forcing is increased gradually to represent the observed changes in forcing due to all the greenhouse gases from 1881 to 1990. From 1990 to 2100 it uses an increase in concentrations represented by the IS92a emissions scenario. The model radiation code includes only CO2, water vapor and ozone. The other radiatively active trace gases are included as equivalent CO2. We used the IS92a emission scenarios. This gives approximately a 0.9%/year increase in equivalent CO2 after 1990. In practice the whole CO2 series was scaled so that the 1880 value matched the model control value (330 ppmv). These data represent monthly averaged surface values of selected variables for the IPCC-Data Distribution Centre. (see also http://www.ipcc-data.org/ )