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 extremize some function has suggested several studies. In particu lar, special attention has been devoted to the possibility that the climate reaches an extremal rate of planetary entropy production. Due to both radi ative and material effects contribute to total planetary entropy production , climatic simulations obtained at the extremal rates of total, radiative o r material entropy production appear to be of interest in order to elucidat e which of the three extremal assumptions behaves more similar to current d ata. In the present paper, these results have been obtained by applying a 2 -dimensional (2-Dim) horizontal energy balance box-model, with a few indepe ndent variables (surface temperature, cloud-cover and material heat fluxes) . In addition, climatic simulations for current conditions by assuming a Br ed cloud-cover have been obtained. Finally, sensitivity analyses for both v ariable and fixed cloud models have been carried out.