Without its natural greenhouse effect, the Earth would be a much less welcoming place. But this beneficial natural phenomenon, which encourages life, is now paralleled by an artificial greenhouse effect caused by mankind. For some years now, the scientific community has been delivering disturbing warnings with increasing firmness: by dint of allowing so-called "greenhouse effect" gases to escape into the atmosphere, produced in particular by the combustion of fossil fuels, has man not become a climatic agent? Such a change would have an impact on mankind, biological diversity and territories. But how can we call into question the increasing use of fossil fuels or indeed intensive farming at the very time when the planet is about to peopled by an unparalleled number of human beings? Would it not be undermining the very foundations of industrial civilisation? Are any other choices possible? How would they allow the deadlines of 2025, 2050 and 2100 to be met? After a contribution in just a century and a half to the deregulation of the climatic conditions of the space vessel Earth, is man up to the task of rectifying the consequences of his past and current excesses and refocusing his action? Is there still time? North-South relations depend on it, as does the fate of future generations. Given the planetary nature of the problem faced by each and everyone, OPECST's intention has been to give to the reader of this report the means to make up his own mind, by adding a CD-ROM on climate changes to this study. Apart from Senator Marcel Deneux's report, this CD-ROM includes some twenty reports or related articles isued by the most authoritative sources (Academy of Sciences, Interministerial Mission on the Greenhouse Effect, etc.) in addition to the Internet sites giving access to other information about climate changes, the greenhouse effect and the future of the Blue Planet.