THE SUNS INFLUENCE ON CLIMATE

Variations of the solar irradiance, as directly measured today or extr apolated to past decades and centuries from instrumental observations or isotopic surrogates, play a significant role in long-term climatic change. The Little Ice Age episode of the XVIIth century has been most likely related to the low solar activity period known as the Maunder Minimum. The observed evolution of the globally average mean surface t emperature seems strongly correlated to the variations of solar irradi ance during the last 2 centuries, even though these variations play a minor role compared to the anthropogenic greenhouse effect. Finally, o bservations indicate possible impacts at decadal time-scales which rem ain difficult to explain on physical grounds.