Maximum entropy production, cloud feedback, and climate change

A steady-state energy-balance climate model based on a global constraint of maximum entropy production is used to examine cloud feedback and the response of surface temperature T to doubled atmospheric CO₂. The constraint ensures that change in zonal cloud amount øo necessarily involves change in the convergence KX of meridional energy flow. Without other feedbacks, the changes in øo, KX and T range from about 2%, 2 Wm^-2 and 1.5 K respectively at the equator to -2%, -2 WM^-2 and 0.5 K at the poles. Global-average cloud effectively remains unchanged with increasing CO₂ and has little effect on global-average temperature. Global-average cloud decreases with increasing water vapour and amplifies the positive feedback of water vapour and lapse rate. The net result is less cloud at all latitudes and a rise in T of the order of 3 K at the equator and 1 K at the poles Ice-albedo and solar absorption feedbacks are not considered. Copynght 2007 by the American Geophysical Union.