Bush aide says warming man-made

By Roger Harrabin Environment analyst, BBC News

Friday Sept. 14, 2007

The US chief scientist has told the BBC that climate change is now a fact.

Professor John Marburger, who advises President Bush, said it was more than 90% certain that greenhouse gas emissions from mankind are to blame.

The Earth may become "unliveable" without cuts in CO2 output, he said, but he labelled targets for curbing temperature rise as "arbitrary".

His comments come shortly before major meetings on climate change at the UN and the Washington White House.

There may still be some members of the White House team who are not completely convinced about climate change - but it is clear that the science advisor to the President and director of the Office of Science and Technology Policy is not one of them.

In the starkest warning from the White House so far about the dangers ahead, Professor Marburger told the BBC that climate change was unequivocal, with mankind more than 90% likely to blame.

Despite disagreement on the details of climate science, he said: "I think there is widespread agreement on certain basics, and one of the most important is that we are producing far more CO2 from fossil fuels than we ought to be.

"And it's going to lead to trouble unless we can begin to reduce the amount of fossil fuels we are burning and using in our economies."