The faint young sun paradox: A finite-time thermodynamic approach
F. Angulo-Brown

Escuela Superior de Fisica y Matematicas - IPN Mexico

Abstract: According to models of stellar evolution, the Sun at the early stages of its main-sequence lifetime had only 70 percent the energy output that it has today. This change in solar luminosity has affected the earth´s radiation balance, in such a manner that two Gyr ago the earth's mean surface temperature would have been below the freezing point of water. However, geological evidence for liquid water as early as 3.8 Gyr has been reported. Thus, radiative balance between Sun and earth along is not sufficient to explain the early presence of liquid water temperatures on earth´s surface. This problem is known as the faint young Sun paradox. Many proposals have been published to solve this paradox. In the present work we propose a finite-time thermodynamic (FTT) approach to obtain liquid water temperature at the early stages of the earth based on a FTT model for air convective cells in the atmosphere. This model uses two modes of atmospheric operation: A maximum power output regime and the so-called ecological regime. Several scenarios of albedo and greenhouse effect are considered.