FEEDBACKS IN A CLIMATE SYSTEM: CLOUD, WATER VAPOR, AND RADIATION INTERACTION

V. P. Meleshko, V. M. Kattsov, P. V. Sporyshev, S. V. Vavulin, and V. A. Govorkova

A series of experiments was conducted with the MGO atmosphere—ocean upper mixed layer model to study climate sensitivity to different parametrizations of cloud—radiation interaction and convection under a doubling of CO2 in the atmosphere. The experiments used different assumptions on clouds and cloud optics behavior under warming climate conditions. In case both the cloud distribution and cloud optics were fixed, global climate warming due to a doubling of CO2 was similar for different convection schemes. When it was assumed that the cloud distribution and cloud optics can change under a doubling of CO2, global climate warming and corresponding changes in a hydrological regime were much dependent on the convection scheme employed. The above differences are due to a vertical cloud rearrangement at low latitudes where convective processes are crucial for global energy redistribution. The increase in cloud optical depth dramatically impacts on climate warming at high latitudes of both hemispheres. Its contribution to climate warming is comparable to that of the earth's surface albedo feedback which is governed by variations in snow—cover and sea—ice extents.