AbstractIn a zonally‐average energy balance climate model (principal features as with Paltridge 1975) with the four unknowns ‐ surface temperatureT, cloud amountN, total meridional heat fluxes within the ocean and the atmosphere Om+Am, and total vertical heat fluxLE+CH, the maximum entropy production by meridional heat fluxes is used as a constraint to solve the system for the four unknowns in all 10 boxes of the model. Since the solution at maximum entropy production by meridional heat fluxes agrees quite well with present mean conditions, this maximum principle is used as a working hypothesis for climate sensitivity studies avoiding the use of fixed cloud amount and meridional heat fluxes. the resulting sensitivities partly agree and disagree with those of similar energy balance climate models. Disagreement is particularly high if an ice‐albedo feed‐back is included. the feed‐back is strongly reduced because of opposing effects of cloud amount in high