Astronomical theory of palaeoclimates.

The astronomical theory of palaeoclimates aims to explain the recurrence of the glacial-interglacial cycles that characterizes the Quaternary climate. It is based upon the latitudinal and seasonal distributions of the energy that the Earth receives from the Sun. Their variations in time depend upon three astronomical parameters: the eccentricity of the Earth's orbit, the inclination of its axis of rotation and the climatic precession. These astronomical variations are in turn amplified by feedback mechanisms in the climate system such as those related to the albedo, the water vapor and other greenhouse gases (CO2 and CH4), the ice sheets and the lithosphere below them. Climate models of different complexity have shown that the long-term variations of the astronomical parameters are the pacemaker of the climatic variations during the Quaternary (and other geological times) at the time scales of tens to hundreds of thousands of years. (C) 2004 Academie des sciences. Publie par Elsevier SAS. Tous droits reserves.