I defer to New Scientist
Climate change sceptics sometimes claim that many leading scientists question climate change. Well, it all depends on what you mean by "many" and "leading". For instance, in April 2006, 60 "leading scientists" signed a letter urging Canada's new prime minister to review his country's commitment to the Kyoto protocol.
This appears to be the biggest recent list of sceptics. Yet many, if not most, of the 60 signatories are not actively engaged in studying climate change: some are not scientists at all and at least 15 are retired.
Compare that with the dozens of statements on climate change from various scientific organisations around the world representing tens of thousands of scientists, the consensus position represented by the IPCC reports and the 11,000 signatories to a petition condemning the Bush administration's stance on climate science.
The fact is that there is an overwhelming consensus in the scientific community about global warming and its causes. There are some exceptions, but the number of sceptics is getting smaller rather than growing.
Of course, just because most scientists think something is true does not necessarily mean they are right. But the reason they think the way they do is because of the vast and growing body of evidence. A study in 2004 looked at the abstracts of nearly 1000 scientific papers containing the term "global climate change" published in the previous decade. Not one rejected the consensus position. One critic promptly claimed this study was wrong - but later quietly withdrew the claim.