"Several independent indicators show an increase in global warming from 1975 to 2003. This increase is mainly due to the increase in the concentration of carbon dioxide," the academy said in conclusion to the report.

"The increase in carbon dioxide, and to a lesser degree other greenhouse gases, is unquestionably due to human activity," said the report, adopted unanimously by academy members.

The report contradicts France's former education minister Claude Allegre, a geochemist, who published a book called "The Climatic Deception" which claimed that carbon dioxide was not linked to climate change.

The report was commissioned in April by Minister for Research Valerie Pecresse in response to hundreds of environmental scientists who complained that Allegre in particular was disparaging their work.

Allegre is a member of the Academy of Sciences and also signed off on the report.

"He has the right to evolve," the academy's president Jean Salencon said. Pecresse said: "The debate is over."

But Allegre told AFP that the document was a compromise and "I have not evolved, I still say the same thing, that the exact role of carbon dioxide in the environment has not been shown."

"Of course it's a compromise, but it's a satisfactory compromise because what I defend, that is the uncertainty in our knowledge about climate change, is explicitly mentioned, the word uncertainty appears 12 times," he said.

In his book, Allegre questioned the work of the UN's Intergovernmental Panel on Climate Change (IPCC) and criticised worldwide mobilisation around "a myth without foundation."

He disagreed with linking climate change and an increase in carbon dioxide in the atmosphere and said clouds or solar activity had more of an influence.

The IPCC, established to sift through scientific research and produce the most authoritative report possible on climate change for world leaders, has been hit by a raft of criticisms and the UN has said it needs a major overhaul.

Glaring errors were revealed in the panel's landmark 2007 Fourth Assessment Report -- notably that Himalayan glaciers which provide water to a billion people in Asia could be lost by 2035, a claim traced to a magazine article.

The Academy's report said that "solar activity, which has dropped slightly on average since 1975, cannot be dominant in warming observed during this period" even if the mechanisms involved "are not yet well understood."

"Major uncertainties remain on how to model clouds, the evolution of marine ice and the polar caps, the connection between the oceans and the atmosphere, the biosphere's evolution and the carbon cycle," the report said.

Allegre wrote that it was impossible to predict the climate's long-term evolution, but the Academy said that "climate evolution predictions of 30 to 50 years are little affected by uncertainties on modelling slow evolution processes."

"These predictions are particularly useful in responding to society's current concerns, worsened by the predictable population growth."

The IPCC's deputy head, Frenchman Jean Jouzel, welcomed the report.

"Even if in this text lots of space is given to the arguments put forward by climate change sceptics, I note that the document clearly reaffirms the IPCC's broad conclusions," he told AFP.

"Clearly sceptics will find some things to make their case. It says that not all is clear about the sun's role. The debate is never over," he said.

The report was the result of written contributions as well as closed-door discussions held at the Academy on September 20 and subsequent exchanges, the Academy said.

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