SINGAPORE (Reuters) - Murderer, liar, fraud, traitor.
Climate scientists, used to dealing with skeptics, are under siege like never before, targeted by hate emails brimming with abuse and accusations of fabricating global warming data. Some emails contain thinly veiled death threats.
Across the Internet, climate blogs are no less venomous, underscoring the surge in abuse over the past six months triggered by purported evidence that global warming is either a hoax or the threat from a warmer world is grossly overstated.
A major source of the anger is from companies with a vested interest in fighting green legislation that might curtail their activities or make their operations more costly.
"The attacks against climate science represent the most highly coordinated, heavily financed, attack against science that we have ever witnessed," said climate scientist Michael Mann, from Pennsylvania State University in the United States.
"The evidence for the reality of human-caused climate change gets stronger with each additional year," Mann told Reuters in emailed responses to questions.
Greenpeace and other groups say that some energy companies are giving millions to groups that oppose climate change science because of concerns about the multi-billion dollar costs associated with carbon trading schemes and clean energy policies.
For example, rich nations including the United States, Japan and Australia, are looking to introduce emissions caps and a regulated market for trading those emissions.
More broadly, the United Nations is trying to seal a tougher climate accord to curb emissions from burning fossil fuels and deforestation blamed for heating up the planet.
Other opponents are drawn into the debate by deep concerns that governments will trample on freedoms or expand their powers as they try to tackle greenhouse gas emissions and minimize the impacts of higher temperatures.
"There are two kinds of opponents -- one is the fossil fuel lobby. So you have a trillion-dollar industry that's protecting market share," said Stephen Schneider of Stanford University in California, referring to the oil industry's long history of funding climate skeptic groups and think tanks.
"And then you have the ideologues who have a deep hatred of government involvement," said Schneider, a veteran climate scientist and author of the book "Science as a contact sport".
The result is a potent mix that has given the debate a quasi-religious tone with some climate critics coming from the right-wing fringe and making arguments as emotive as those raised in the abortion and creationism debates in the United States.
The debate has largely become drawn along political lines, at least in the U.S., where opponents in the Republican Party question climate science and raise doubts over the need to implement greener policies such as those espoused by climate change campaigner and former Vice President, Al Gore.
In a party conference in April, Republican firebrand Sarah Palin, a potential 2012 presidential nominee, mocked what she called the "snake-oil-based, global warming, Gore-gate" crowd.
The green lobby is also to blame. Exaggerations by some green interest groups, which have at times over-played the immediacy of the problem to bring about a groundswell of support for a new U.N. climate treaty and green policies, have given skeptics plenty of ammunition.
Skeptics also point to admissions in a 2007 report by the U.N.'s Intergovernmental Panel of Climate Change that there is a 10 percent chance global warming is part of a natural cycle.
The same report says there's a 90 percent probability that climate change is due to human activities led by burning fossil fuels. Nevertheless, the skeptics demand 100 percent certainty, something that researchers say is impossible.
Scientists and conservationists say some anti-climate change lobbyists are funded by energy giants such as ExxonMobil, which has a long history of donating money to interest groups that challenge climate science.
According to a Greenpeace report released last month, ExxonMobil gave nearly $9 million to entities linked to the climate denialist camp between 2005 and 2008.
The report, using mandatory SEC reporting on charitable contributions, also shows that foundations linked to Kansas-based Koch Industries, a privately owned petrochemical and chemicals giant, gave nearly $25 million.
Koch said the Greenpeace report mischaracterized the company's efforts. "We've strived to encourage an intellectually honest debate on the scientific basis for claims of harm from greenhouse gases," the company said in a note on its website.
ExxonMobil makes no secret of funding a range of groups, but says it has also discontinued contributions to several public policy research groups.
"We contribute to an array of public policy organizations that research and promote discussion on climate change and other domestic and international issues," the company says on its website.
Stanford's Schneider has dealt with skeptics for years. But this time, he says, it's different.
"I don't see it stopping," said Schneider by telephone. "I see it intensifying. The ugliness is what's new."
One of the thinly veiled death threats that Schneider has received says: "You communistic dupe of the U.N. who wants to impose world government on us and take away American freedom of religion and economy -- you are a traitor to the U.S., belong in jail and should be executed."
Scientists say there is a wealth of data showing the planet is warming, that it's being triggered by rising levels of greenhouse gases such as carbon dioxide and that man is to blame.
Skeptics counter this by saying that rising CO2 levels is natural and harmless and that it's impossible for mankind to influence the way the planet functions. Others play up doubts or errors in some scientific studies to undermine it all.
Many also say warming has stalled, pointing to the recent burst of cold weather in the Northern Hemisphere as evidence of global cooling, even though satellite data show that, overall, November 2009 to January 2010 was the warmest Jan-Nov the world has seen since satellite temperature data began in 1979.
Then came the release of emails hacked late last year from a British climate research unit.
The "climategate" emails, totaling more than 1,000, were stolen from the University of East Anglia's Climate Research Unit (CRU), and involve correspondence between director Phil Jones and other leading climate scientists, including Schneider and Mann.
The emails led to allegations the scientists fudged data to bolster the case for mankind causing global warming, setting off a surge of criticism across the Internet accusing climate scientists of a massive hoax.
"This whole thing has gone viral on the Internet," said Cindy Baxter of Greenpeace, author of a recent report "Dealing in Doubt: The Climate Denial Industry and Climate Science."
"You've got all those voices out there on the blogosphere who are then picked up and echoed," she told Reuters.
The University of East Anglia has been a particular target.
"There have been an awful lot of abusive emails since 'climategate' broke," said university spokesman Simon Dunford.
Skeptics were accused of very selectively choosing only a small number of the hacked emails and taking comments out of context to misrepresent the scientists' meaning.
A British government inquiry cleared Jones of any wrongdoing, but said CRU was wrong to withhold information from skeptics.
Mann, who was accused of falsifying data, was cleared of any wrongdoing by an internal investigation by Penn State University.
Skeptics also accused the U.N.'s Intergovernmental Panel on Climate Change of supporting flawed science after several errors in a major 2007 report surfaced.
The errors, including a reference to a non-peer reviewed study that Himalayan glaciers would melt by 2035, represent a fraction of the conclusions in the report, the main climate policy guide for governments, which is based on the work of thousands of scientists.
The IPCC has defended its work and has ordered a review. Many governments, including the United States, Britain and Australia have also reiterated their faith in the IPCC.
For climate scientists, truth and trust are at stake.
"In general, the battle for public opinion is being lost," said Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. His emails were also hacked in the CRU incident.
"There is so much mis-information and so many polarized attitudes that one can not even hold a rational discussion or debate. The facts are certainly lost or glossed over in many cases. The media have been a bust."
Schneider said the mainstream media had failed to do "its job of sorting out credible from non-credible and not giving all claimants of truth equal status at the bargaining table".
Across the Internet, the climate science debate is being played out in a myriad of climate skeptic sites and blogs as well as sites defending the science of human-induced climate change.
One high-profile site is climatedepot.com, run by Marc Morano, a former aide to U.S. Republican Senator James Inhofe, who is an outspoken critic of climate change policies.
Morano, who told Reuters he had also been the target of abusive emails, has been quoted as saying that climate scientists should be publicly flogged.
"The global warming scientists need to feel and hear the public's outrage at their shenanigans like "climategate" ... There is no advocacy of violence or hint that people should threaten them," Morano said, adding: "Public outrage is healthy."
Another prominent climate change denialist, Christopher Monckton, who's associated with the U.S.-based Science and Public Policy Institute, told Reuters he doesn't condone the coordinated attack on climate scientists, saying that he, too, was a victim.
He said his main aim was to expose what he calls the "non-problem of global warming" and in an email interview with Reuters accused climate change scientists of being "increasingly desperate to discredit anyone who dares to point out that the Emperor has no clothes".
Media commentators have added their voices, polarizing public opinion further. In the United States, conservative radio talkshow host Rush Limbaugh said on the air last November that climate change was a massive hoax and that all climate scientists involved should be "named and fired, drawn and quartered, or whatever it is".
In Australia, just as in the United States, the level of abuse also coincides with media appearances or the release of peer-reviewed scientific work on climate change.
"Each time I have a media profile in terms of media reports on scientific papers, major presentations, there is a flurry. So if I am on TV, or radio there ends up being a substantial increase," said David Karoly of the University of Melbourne.
"One of the purposes for the attacks is either an intention to waste my time or to distract my attention essentially from communication about climate change science or even undertaking research, and it's also perhaps intended to make me concerned about my visibility."
"We get emails to say we're destroying the Australian economy, we get emails to say it will be our fault when no one in Australia can get a job. We get emails just basically accusing us of direct fraud and lying on the science," said Andy Pitman, co-director of the Climate Change Research Center at the University of New South Wales in Sydney.
"My personal reaction to them is personal recognition that this means we are a threat to the sorts of people who would be trying to prevent the finding of solutions to global warming."
Pitman said a major problem was trying to satisfy demands for absolute proof of human-induced global warming.
"There is no proof in the context that they want it, that the earth goes around the sun. They are demanding a level of proof that doesn't exist in science.
"And then they say when you can't prove it to the extent that they want, then clearly that means there isn't any evidence, which of course is a logical fallacy."
Better communication about the science is key, scientists say, even if they complain that many skeptics are reluctant to debate the science on a level playing field.
"One of the ways I describe it (the debate) is it's very asymmetric," said Roger Wakimoto, director of NCAR in Colorado.
"It's very difficult to counter someone who just says 'you're wrong. I think this is a scam'. How do you respond to that? ... They haven't done any research, they haven't spent years looking into the problem. This is why it's asymmetric," he said.
"We like to go into a scientific debate, show us you're evidence and we'll tell why we agree or disagree with you. But that's not what the naysayers are doing," Wakimoto added.
"We've never experienced this sort of thing before," he said of the intense challenges to climate science and the level of email and Internet traffic.
All the climate change scientists with whom Reuters spoke said they were determined to continue their research despite the barrage of nasty emails and threats. Some expressed concern the argument could turn violent.
"My wife has made it very clear, if the threats become personalized, I cease to interact with the media. We have kids," said one scientist who did not want to be identified.
Additional reporting by Alister Doyle in Oslo; Editing by Megan Goldin