Extremal principle of entropy production in the climate system

Paltridge found reasonable values for the most significant climatic variabl es through maximizing the material transport part of entropy production by using a simple box model. Here, we analyse Paltridge's box model to obtain the energy and the entropy balance equations separately. Derived expression s for global entropy production, which is a function of the radiation field , and even its material transport component, are shown to be different from those used by Paltridge. Plausible climatic states are found at extrema of these parameters. Feasible results are also obtained by minimizing the rad iation part of entropy production, in agreement with one of Planck's result s, Finally, globally averaged values of the entropy flux of radiation and m aterial entropy production are obtained for two dynamical extreme cases: an earth with uniform temperature, and an earth in radiative equilibrium at e ach latitudinal point.