"For every single scientist that tells you (global warming is) happening and that it's our fault...I can stack up another group of reports that say just the opposite."

Tom Tancredo on Tuesday, May 15th, 2007 in Columbia, S.C.

Most scientists say humans cause warming

At a debate in South Carolina, Tancredo said he could match, stack for stack, the scientific reports that support global warming with those that do not.

In fact, the stacks would be pretty lopsided.

Tancredo is wrong to suggest that climate scientists are evenly split. The overwhelming consensus among them is that humans are the main cause of global warming.

A recent study by the Intergovernmental Panel on Climate Change, a group of scientists from more than 130 nations, concluded that there is overwhelming evidence that warming is caused by human activity.

Their February 2007 report said warming was "unequivocal" and that most of it has been caused by greenhouse gas concentrations caused by humans. The report said that humans have caused a significant increase in atmospheric concentrations of carbon dioxide, methane, and nitrous oxide since 1750.

Yes, there have been dissenting studies over the years about global warming. But the IPCC is an effort to forge an international consensus. It has included more than 2,500 expert reviewers, more than 800 authors and more than 450 lead authors working for the past six years.