Feedback effects of atmospheric CO2 -induced warming

Abstract

Using a thermodynamic climate model, temperature and precipitation changes due to a doubling of atmospheric CO2 content, including the corresponding feedback temperature increases of water vapor, snow-ice, and cloudiness, are evaluated. The feedback factors of the thermodynamic model are similar to those of Hansen et al. (1984) and Schlesinger (1986). The feedback factor of all three mechanisms combined is 4.0. The results depend mainly on the content of water vapor in the CO2 band (12-19 m). The temperature increase due to a doubling of CO2 is 1.2° C when there is water vapor in the band, and 3.5° C when there is no water vapor. Therefore, a possible cause of the strong differences in the solutions obtained by different models is the discrepancy in the amount and distribution of water vapor in the atmosphere, and in the treatment of its effect in the CO2 band.