The study, published in this month's issue of Environmental Politics, analyzed books written between 1972 and 2005 that deny the authenticity of environmental problems. The researchers found that more than 92 percent of the skeptical authors were in some way affiliated to conservative think tanks - non-profit research and advocacy organizations that promote core conservative ideals.  

While many environmental skeptics are known to work for these think tanks, the study is the first to provide a quantitative analysis of the relationship. The popular media often regard environmental skeptics as independent experts, despite their connection to industry-funded campaigns that seek to de-legitimize sound environmental science reports, especially on climate change, says lead author Peter Jacques, an environmental politics professor at the University of Central Florida.

"A lot of skeptics might say they are independent voices, but it's clear there is an organization behind the skeptical discourse," Jacques said. "If not for conservative think tanks, we wouldn't be having this same discussion; we wouldn't be hung up on whether climate change is real."

The review analyzed 141 books, which the authors consider the largest compilation of the environmental skepticism genre and the majority of all English-language skepticism books. An author was "affiliated" to a think tank if the organization published the book or if the author ever - before or after the book was published - held a position with the organization, wrote for an organization's publications, or delivered lectures sponsored by the organization.

The U.S. conservative movement has lead opposition to international environmental regulation since the 1992 Earth Summit in Rio de Janeiro. In the years since, the movement has succeeded in undermining the credibility of many environmental issues, said Riley Dunlap, a sociology professor at Oklahoma State University, who co-authored the study. "From the [political] right, there's no longer a sense of neutral, objective science - only liberal or conservative - and that's an unfortunate trend," Dunlap said.

Many skeptics say that they form their opinion despite their affiliation to think tanks or industry. For instance, Ronald Bailey, a correspondent for the ExxonMobil-funded Reason Foundation and former fellow for the conservative Competitive Enterprise Institute, recently reversed his stance as a climate change denier. His original skepticism was the result of inconsistent temperature datasets. He was not "passing along misinformation supplied to me during expensive lunches," he wrote in the article Confessions of an Alleged ExxonMobil Whore.

The authors say skeptics like Bailey have every right to voice their opinion. But the statements of a few think tank-supported experts should not be regarded as equal to scientific findings that have been vetted through an intense peer-review process, they say. "We want to allow a cacophony of voices in public policy," Jacques said. "Where we get into problems is where we fail to evaluate the voices; we fail to evaluate the merit of the claim."

Ben Block is a staff writer with the Worldwatch Institute. He can be reached at bblock@worldwatch.org.