COPENHAGEN, Denmark - The head of the U.N. panel on climate change compared him to Hitler. Another leading scientist called him a parasite. A third described his latest book as a "stealth attack" on mankind.

The list of allegations against Bjoern Lomborg, one of the world's leading climate-change skeptics, almost reads like an indictment for war crimes.

As Al Gore shows off his Nobel Peace Prize and world policy-makers decide on a new strategy for saving the planet, climate-change contrarians say they have been elbowed out of the debate. They say mainstream scientists have stifled healthy intellectual discourse by demonizing dissenters as oil-industry lobbyists or lunatics.

"I really think it reflects entirely on them," said Lomborg, a mild-mannered Danish statistician who asserts that global warming is not a big threat and that international treaties requiring sharp and immediate cuts in carbon emissions would cost a lot but do little good.

Angry words and table-pounding, he said, only show "that your argument is not that strong."

Climate-change experts counter that the contrarians are no longer relevant because the evidence now is overwhelming that human-made warming will have dangerous consequences if left unchecked.

"Their claim that debate is being stifled has the same credibility as members of the Flat Earth Society complaining about the round Earth mafia," NASA scientist Gavin Schmidt said.

Lomborg accepts that the Earth is warming because of humans. But he says that a changing climate, including the threat posed by rising sea levels to small island nations, is a less urgent problem than, for example, AIDS or malnutrition.

It is a view that has infuriated advocates of immediate action by the world's governments.

"What is the difference between Lomborg's view of humanity and Hitler's? You cannot treat people like cattle," Rajendra Pachauri, the chairman of the Intergovernmental Panel on Climate Change - which shared the Nobel with Gore - was quoted as saying in a 2004 interview with Danish newspaper Jyllands-Posten.

Pachauri now disavows the comments. "I was misquoted. That was taken out of context," he told the Associated Press last week. But Jyllands-Posten reporter Lars From, who conducted the interview, insisted Pachauri was correctly quoted.

On Feb. 9, Boston Globe columnist Ellen Goodman wrote that "global warming deniers are now on a par with Holocaust deniers, though one denies the past and the other denies the present and future."

Some mainstream scientists say that kind of rhetoric is going too far.

"There is never a reason for name-calling, and any time someone plays the Hitler card, it's usually an obvious sign of desperation in the debate," said Michael Mann, director of Pennsylvania State University's Earth System Science Center.

But Mann said that contrarians "who choose to mislead the public" on what science says about climate change cannot expect to escape being chastised.