In recent months, a group called the Cooler Heads Coalition - a creation of the Washington-based Competitive Enterprise Institute (CEI) - has fostered a public image of climate science as a criminal conspiracy. The CEI itself has accused NASA, the largest funder of climate science, of faking important climate data sets. In February, U.S. Sen. James Inhofe of Oklahoma, whose positions are frequently cited and promoted by CEI, called for a criminal investigation of 17 climate scientists from a variety of institutions for allegedly falsifying or distorting data used in taxpayer-funded research.

The recent shift in the community of global warming deniers from merely attacking mainstream climate scientists to alleging their involvement in criminal activity is an unsurprising but alarming development in the long campaign to discredit the established scientific fact that burning fossil fuels is causing the world to warm. This latest escalation fits seamlessly into a decades-old pattern of attempts to deny the reality of environmental ills - smoking, acid rain, ozone depletion, and global warming. Similar or even identical claims have been promoted for decades by other free-market think-tanks, including the American Enterprise Institute, the Cato Institute, the Heartland Institute, and, most persistently, the George C. Marshall Institute. These think tanks all have two things in common: They promote free-market solutions to environmental problems, and all have long been active in challenging the scientific evidence of those problems.

In researching a book on global warming deniers, we often felt demoralized by the efficacy of doubt-mongering tactics and depressed that the American public had been repeatedly fooled by the same strategy and tactics. On the other hand, we felt cautiously optimistic because disputes over other issues - tobacco smoking, acid rain, second-hand smoke, and the ozone hole - ended with the scientific evidence prevailing, and with regulation that (however delayed or weakened) addressed the problem.

Global warming was the great unfinished story, but with the mainstream media and many politicians acknowledging the reality of global warming in recent years, it seemed that there was real progress. "The debate is over," California Gov. Arnold Schwarzenegger declared in 2005. "We know the science. We see the threat posed by changes in our climate."

Now it seems that progress has been reversed. In recent months, as the U.S. Senate prepared to consider climate and energy legislation, there has been a stepped-up effort on a broad front to belittle the overwhelming evidence of human-caused global warming. As they did with smoking and acid rain, the so-called global warming skeptics have had one overriding goal: to sow doubt in the public's mind and head off government regulation.

In the case of global warming, there is strong evidence that this contrarian campaign is enjoying success, with recent polls showing that more than half of Americans are not particularly worried about the issue and that fully 40 percent believe there is major disagreement among scientists about whether climate change is even occurring. This confusion is no doubt due, at least in part, to the persistent campaigns of obfuscation by the Competitive Enterprise Institute and other global warming deniers who use right-wing talk radio, the Internet, and television programs such as Fox News to propagate their message of doubt.

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The story begins with the tobacco companies' long-running effort to cast doubt on the links between cigarette smoking and human health effects, including lung cancer. One of the scientists the tobacco industry recruited to this cause was Frederick Seitz. Seitz was a distinguished solid-state physicist, who believed strongly in the role of science and technology in defending the United States during the Cold War. In the late 1950s and 1960s he rose to high levels in national science policy, serving, among other positions, as president of the U.S. National Academy of Sciences.

However, in 1979, toward the end of his career, he took a new job: running a $45 million program for R.J. Reynolds Tobacco to support scientific research to defend the "product" - that is to say, tobacco - long after scientists and physicians had come to virtually unanimous agreement on the overwhelming harm that it caused.

In the words of one industry document, Seitz's program was to develop "an extensive body of scientifically, well-grounded data useful in defending the industry against attacks." The goal was to fight science with science - or at least with the gaps and uncertainties in existing science, and with scientific research that could be used to deflect attention from the main event. Like the magician who waves his right hand to distract attention from what he is doing with his left, the tobacco industry would fund distracting research, such as studies on the dietary causes of atherosclerosis and the role of patients' psychological attitudes on the progression of disease.

In 1984, Seitz took up another cause, joining with two other prominent physicists, William Nierenberg and Robert Jastrow - both also long active in space and weapons programs - to found the George C. Marshall Institute. They created the institute to defend President Reagan's Strategic Defense Initiative (SDI) from attacks by the mainstream physics community. The Marshall Institute drew its funding from a handful of conservative political foundations, and it defended SDI by loud claims of Soviet military superiority, claims that were found only a few years later - when the USSR disintegrated and the Cold War ended - to have been exaggerated, at best. However, although the Soviet threat was gone and the Cold War was won, the institute didn't go out of business. Instead, it found a new enemy: environmentalists.

In the early 1980s, Nierenberg had chaired a major National Academy of Sciences review of global warming. Scientists had formed a consensus in the late 1970s that global warming was likely to result from increasing greenhouse gases released by burning fossil fuels, and that this would have serious consequences: glaciers and polar ice sheets would melt, causing sea levels to rise and inundating coastlines and major port cities; deserts would expand, reducing food production; and rapid habitat change could lead to serious biodiversity loss. But as chairman of the panel, Nierenberg rejected the conclusions of his fellow physical scientists and recruited several economists who argued that, rather than trying to prevent climate change, we should simply wait and see what happened and then adapt as events unfolded. If adaptation proved impossible, humans could always migrate, Nierenberg concluded, ignoring the overwhelming historical evidence of the widespread human suffering that has typically accompanied mass migration.

Nierenberg also joined with another physicist, S. Fred Singer, to undermine regulatory action on sulfur dioxide, the principal cause of acid rain. In response to two National Academy reports suggesting that acid rain was real and serious, and its primary causes known, President Reagan commissioned an independent peer review of the existing scientific evidence. Most of the panel members were, actually, independent, and agreed with the National Academy that regulatory action to control sulfur emissions was warranted. However, Nierenberg and Singer worked to challenge that conclusion, adding a policy-oriented appendix by Singer - which was not approved by the entire panel - that first advocated free-market approaches to controlling pollution, and then concluded (but without a real quantitative analysis) that the cost of reducing acid rain would very likely exceed the benefits. Nierenberg also worked behind the scenes with White House Science Advisor George Keyworth to soften the conclusions of the report's executive summary and to make them seem more ambiguous than they had originally been. (Something Nierenberg would later accuse climate scientists of doing - only in the reverse.)

Despite these machinations, the acid rain report was still stronger than the Reagan White House wanted, and the administration delayed releasing it until after Congress had defeated pending acid rain legislation. Several congresspersons later stated that had the peer review report been available when the vote was taken, it might well have gone the other way.

It took several more years before the administration of George H. W. Bush implemented an acid rain reduction program organized around a cap-and-trade system. In one sense, this program has worked, reducing acid deposition in the Northeast by more than 50 percent, and - contrary to Singer's claims - at one-tenth of the projected cost. But it was also too little, too late. Continued work by ecologists such as Gene Likens shows that Northeastern forests are still dying.

In the late 1980s, the Marshall Institute turned to the denial of global warming. As scientific evidence emerged that warming was not only going to happen, but was perhaps already happening, the institute's attacks became stronger and more unprincipled. These "contrarians" - because their positions were contrary to the majority scientific view - began taking evidence out of context, cherry-picking data, and misrepresenting what was actually being published in the scientific literature. For example, they distributed a "white paper" in 1989 falsely claiming that a review from NASA climate scientist James Hansen showed that recent warming was largely due to increased solar activity.

When confronted with incontrovertible evidence that their arguments and cherry-picked facts were incorrect, the deniers refused to correct their mistakes and continued to spread the same misinformation. Indeed, as the science strengthened, and the evidence of the human fingerprint on the climate system began to strongly emerge, the contrarian attacks became more virulent, more unprincipled, and more personal.

In 1995, the Intergovernmental Panel on Climate Change prepared to release its second assessment report, which would declare that the human effect on climate was now "discernible." That same year, a fossil-fuel industry-funded group called the Global Climate Coalition accused Benjamin Santer, a scientist at the Lawrence Livermore National Laboratory and lead author of a key IPCC chapter, of committing "scientific cleansing" - that is, of removing mention of uncertainties in the chapter to make global warming appear more certain than it was. The men of the Marshall Institute then splashed that accusation onto the op-ed pages of the Wall Street Journal. Investigations found nothing untoward had happened. All Santer had done was include new findings on global warming suggested by fellow scientists during the peer-review process and to clarify language that was also suggested in the peer review process. Various colleagues and IPCC officials defended Santer and tried to set the record straight, but it didn't matter. Indeed, in 2007, Fred Singer repeated the charges in a new book, and they continue to be repeated on the Internet today.

If all this sounds familiar, it should. Similar attacks were launched against the scientific evidence of the ozone hole, of second-hand smoke, and of the harms of DDT. As one tobacco executive put it in 1969, "Doubt is our product, since it is the best means of competing with the ‘body of fact' that exists in the minds of the general public." Casting doubt about climate science is simply part of the effort to prevent regulation of fossil fuels. The point of merchandising doubt was, and remains, the prevention of government regulation.

These opponents of science are free-market fundamentalists, unwilling to accept that global warming and many other pollution-induced ills are market failures, and that government action of some kind will be needed to address it. Market fundamentalists believe that free markets are the solution to social problems and government intervention can only do harm. The reality, however, amply demonstrated by experience, is that pollution is external to the market system - there's no cost to dumping waste into the air and water. And as Lord Nicholas Stern has recently noted, global warming is the biggest market failure of them all. But this is yet another truth that the free market fundamentalists prefer to ignore.

Meanwhile, the contrarians' campaigns continue, and with significant success: Many Americans accept the deniers' allegations as true, or at least are confused by them, and therefore do not know what to think or whom to trust. Science has been effectively undermined, which has eroded public support for the decisive action needed to avoid the worst effects of global warming.