But Benny J. Peiser, a social anthropologist in Britain who runs the Cambridge-Conference Network, or CCNet, an Internet newsletter on climate change and natural disasters, challenged the claim of scientific consensus with examples of pointed disagreement.

"Hardly a week goes by," Dr. Peiser said, "without a new research paper that questions part or even some basics of climate change theory," including some reports that offer alternatives to human activity for global warming.

Geologists have documented age upon age of climate swings, and some charge Mr. Gore with ignoring such rhythms.

"Nowhere does Mr. Gore tell his audience that all of the phenomena that he describes fall within the natural range of environmental change on our planet," Robert M. Carter, a marine geologist at James Cook University in Australia, said in a September blog. "Nor does he present any evidence that climate during the 20th century departed discernibly from its historical pattern of constant change."

In October, Dr. Easterbrook made similar points at the geological society meeting in Philadelphia. He hotly disputed Mr. Gore's claim that "our civilization has never experienced any environmental shift remotely similar to this" threatened change.

Nonsense, Dr. Easterbrook told the crowded session. He flashed a slide that showed temperature trends for the past 15,000 years. It highlighted 10 large swings, including the medieval warm period. These shifts, he said, were up to "20 times greater than the warming in the past century."

Getting personal, he mocked Mr. Gore's assertion that scientists agreed on global warming except those industry had corrupted. "I've never been paid a nickel by an oil company," Dr. Easterbrook told the group. "And I'm not a Republican." -- The New York Times