A statistical-dynamical climate model is used for investigating the relative contribution of the changes in the radiation budget and surface air temperature due to the increase of the anthropogenic greenhouse gases predicted for 2100 on the basis of IPCC SRES A1FI (the highest greenhouse level scenario). Five experiments are performed considering the changes in concentrations of (1) CO2, (2) CH4, (3) N2O, (4) tropospheric O3, and (5) all the changes together. The results show that the mean global planetary absorbed solar radiation increases in response to the predicted conditions according to the scenario A1FI for year 2100 (A1FI-2100). This is due to the effect of O3 absorptions. This increase leads to a decrease in the mean global planetary net thermal infrared radiation emitted to space by the Earth-atmosphere system to space and to an increase in mean global planetary net radiation. These changes are controlled mainly by the increase in CO2 concentration. The changes in the radiation budget due to N2O and CH4 are small. The mean global surface air temperature response to the predicted conditions for A1FI-2100 was +0.59¿C. The change in CO2 concentration is responsible for an increase of +0.49¿C. The higher increases occur in the polar regions: +2.15¿C (at 85¿S) and +1.55¿C (at 85¿N) in the case of the predicted conditions for A1FI-2100. Additional experiments indicate that the changes in surface air temperature are similar in the cases of the predicted conditions for A1FI-2100 and 4 ¿ CO2, 2 ¿ CO2 and 4 ¿ N2O, and in 2 ¿ N2O and 4 ¿ CH4.