Studies of climate evolution during past times allows to investigate climate mechanisms and in particular interactions between atmosphere, ocean, ice  and continents. A good understanding climate mechanisms is indeed mandatory to evaluate impact of human activities on climate evolution in the next decades and centuries. Collected paleoclimatic data are therefore used to reconstruct past climatic changes (in particular rapid variations) and to characterize and model involved climatic mechanims.

Studies mainly focus on two time scales :

• The first one is devoted to climatic changes at the geological times, with a focus on the last climatic cycles and on the interactions between climate and environment. Specific effort is done for reconstruction of paleclimatic series from polar ice cores and sediments from marine cores and from continental series. This scientific studies attempt to reconstruct past climatic states in order to understand how the climate reacted to low evolution of the insolation and radiative balance , and to ice sheets and marine circulation instabilities which caused abrupt climatic changes.
• The second one is devoted to recent past, i.e. the last centuries , for which records at high resolution (better than one year) can be obtained. These investigations allow to place variations measured during the last century in the context of the natural variability of the last hundred and thousand of years , and to examine precisely the causes of these variations.

For these two actions modeling is fundemental and has a federating role to understand mechanisms involved in the observed climatic changes. A specific effort is put on the role of the atmosphere, the ocean, and vegetation over the last climatic cycle . It is now extended to recent past , with the use of the coupled atmosphere-ocean model.