Climate evolution: from the recent past to the future

The aim of this article is twofold. We first summarize our current scientific knowledge about the potential influence of human activities on climate. This review is largely based on the conclusions of the 1995 IPCC report (International Panel on Climate Change). An increase in atmospheric concentrations of greenhouse gases has been observed since 1750 (CH4 = 145 %; CO2 = 30 %; N2O =15 %) and in the temperature of the Earth's surface since 1860 (between 0.3 and 0.6 deg C). This report suggests a discernable human influence on climate and predicts significant global warming for the next century (1 to 3.5 deg C) as a result of the anthropogenic increase of the greenhouse effect. We then show how studies of past climates have, over the last ten years, contributed to this problem by providing information relevant to the future of our climate. Important results concern the existence of a relationship between climate and concentrations of greenhouse gases for more than 200 000 years, the discovery of rapid climatic changes (∼ 10 deg C in a few decades in Greenland) and the reconstruction of recent climate showing that the 20. century is the warmest since 1 400 AD. (authors)