Extremal climatic states simulated by a 2-dimensional model Part I: Sensitivity of the model and present state

The criterion, based on the thermodynamics theory, that the climatic system tends to extremizesome function has suggested several studies. In particular, special attention has been devotedto the possibility that the climate reaches an extremal rate of planetary entropy production.Due to both radiative and material effects contribute to total planetary entropy production, climatic simulations obtained at the extremal rates of total, radiative or material entropy productionappear to be of interest in order to elucidate which of the three extremal assumptionsbehaves more similar to current data. In the present paper, these results have been obtainedby applying a 2-dimensional (2-Dim) horizontal energy balance box-model, with a few independentvariables (surface temperature, cloud-cover and material heat fluxes). In addition, climaticsimulations for current conditions by assuming a fixed cloud-cover have been obtained. Finally, sensitivity analyses for both variable and fixed cloud models have been carried out.