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 showed off his Nobel Peace Prize and world policy-makers hammered out 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 says global warming isn't 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 man-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," said NASA scientist Gavin Schmidt.
Lomborg accepts that the Earth is warming because of man, but says 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.
Hitler controversy
It's 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, was quoted as saying in an April 20, 2004 interview with Danish newspaper Jyllands-Posten.
Pachauri now disavows the comments, telling the AP last week: "I was misquoted. That was taken out of context." 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.
However, he added, contrarians "who choose to mislead the public" on what science says about climate change cannot expect to escape being chastised.
Scope now the big issue
That the planet is getting warmer is well-documented by scientific data, so skeptics now mainly challenge the majority view on the scope of the problem.
"Whether or not it's happening is not the point. It's obviously happening," said Pat Michaels, a senior fellow of environmental studies at the libertarian Cato Institute in Washington, D.C.
"How much will it be ... and what should you do about it? That's where the debate should be. But that debate is being driven by very shrill rhetoric."
Another contrarian, meteorology professor Richard Lindzen at the Massachusetts Institute of Technology, said proponents of the predominant view on global warming started trying to stamp out dissent long ago.
"The harassment 15 years ago and earlier pretty much succeeded. Those entering the field thereafter knew the ground rules," Lindzen wrote in an e-mail.
While Lindzen is a scientist, Lomborg irks his opponents partly because he looks at global warming from an economist's perspective. He's not a climate scientist nor does he claim to be.
But critics say he misleads nonscientific audiences about the dangers of a warmer world with crude cost-benefit analyses, like his contention that if warming means more people will die from heat waves, then it must also mean fewer will be dying from cold.
"I hold him responsible for possibly delaying the debate on climate change by two-three years," said Jacqueline McGlade, the head of the European Environment Agency, a European Union body.
In 2001, Pulitzer Prize-winning biologist E.O. Wilson described "contrarians like Lomborg" as "the parasite load on scholars who earn success through the slow process of peer review and approval."
Two years later a Danish panel of scientists accused Lomborg of fabricating data and manipulating facts in his first book, "The Skeptical Environmentalist." Denmark's government later criticized the panel, saying it had treated Lomborg unfairly.
His newly released book on climate change, "Cool It," has also met sharp criticism. In a review in the Washington Post, Australian scientist Tim Flannery called it "a stealth attack on humanity's future."
No Lomborg-Gore debate
Many of Lomborg's opponents around the world are willing to take him on in debates, but he hasn't been able to go head-to-head with the most prominent climate campaigner of them all — Al Gore.
The former U.S. vice president received the Nobel Peace Prize on Monday together with Pachauri, representing the IPCC, an award which many see as the ultimate recognition for the fight against climate change.
Lomborg says Gore pulled out of an interview this year with Jyllands-Posten, the Danish paper, when he found out that Lomborg also had been asked to attend.
Another opportunity for a confrontation arose when Lomborg and a panel of climate experts were invited to listen to Gore speak to BBC staff in London.
"The curious thing is that ... because I was there, we could not be in the room when he was giving the talk. So we all had to sit and wait in the green room," Lomborg said.
McGlade, of the EEA, who also was invited to the event, confirmed Lomborg's description of what happened. She added, however, that Gore routinely debates people with opposing views.
Lomborg says his arguments are gaining traction — if not in the public debate, then among policy makers.
"It's true my opponents seem to have won the battle of words, but it seems to me I've won the battle of the reality," he said. "Because nations are actually doing very little about climate change."