Excerpt from article in New York times

“On environmental issues, Mr. Bush appeared unfamiliar with an administration report delivered to Congress on Wednesday that indicated that emissions of carbon dioxide and other heat-trapping gases were the only likely explanation for global warming over the last three decades. Previously, Mr. Bush and other officials had emphasized uncertainties in understanding the causes and consequences of global warming.

The new report was signed by Mr. Bush's secretaries of energy and commerce and his science adviser. Asked why the administration had changed its position on what causes global warming, Mr. Bush replied, "Ah, we did? I don't think so."

Scott McClellan, Mr. Bush's press secretary, said later that the administration was not changing its position on global warming and that Mr. Bush continued to be guided by continuing research at the National Academy of Sciences”