Résumé
Long-term climatic changes, such as glacial-interglacial cycles, are usually explained in term of changes in solar energy received at the top of the atmosphere. In particular, daily insolation in the high Northern Hemisphere latitudes during summer is widely used in interpreting palaeoclimate records. This insolation forcing is strongly marked by changes in precession. However, some climate variations are much more imprinted by changes in obliquity. This was the case for sea surface temperature in the North Atlantic during the Eemian period, as well as for the Vostok ice core deuterium excess history over the last 250 ka. Therefore, we investigate the insolation forcing in order to identify characteristics that could explain the observed climate response. This is mainly the case for annual mean insolation variations. Simple hypotheses for how this forcing could act on climate are also suggested, these being mainly related to changes in the moisture transport induced by the annual insolation gradient between low and high latitudes. Along these lines, a simple conceptual model of annual mean temperature variations illustrates the role of annual mean insolation on climate. Abstract Copyright (2004) Elsevier, B.V.