In the late 1970s, scientists first came to a consensus that global warming was likely to result from increasing greenhouse gases released by the burning of fossil fuels. This idea had been around since the turn of the century, but the development of computer models made it possible to make quantitative predictions. Almost immediately, a small group of politically connected and conservative scientists began to question this consensus. As empirical scientific data mounted up, their attacks became more unprincipled. These conservative scientists used data selectively and often misrepresented the conclusions of many studies undertaken by the scientific community.
In 1992, world leaders gathered in Rio de Janeiro to sign the United Nations Framework on Climate Change. President George W Bush promised to translate the written document into "concrete action". Three years later, the Intergovernmental Panel on Climate Change (IPCC) declared that the human impact on the earth's climate was no longer a prediction but an observable fact.
In the early 1990s, a group of skeptics claimed that Roger Revelle, one of the first climate scientists, had changed his mind about global warming and no longer believed it was a serious problem. The claim was repeated through several news outlets, including the Washington Post. When a graduate student named Justin Lancaster - who had worked closely with Revelle before his death in 1991 - tried to insist that Revelle had not changed his view, he was sued for libel. Lancaster was obliged to settle out of court. The claim was repeated again and again, and even today, exists on the Internet.
In 1996, when the IPCC released its second assessment report, stating that the human impact on climate was "discernible", a fossil-fuel-industry-funded group called the Global Climate Coalition accused the IPCC author Benjamin Santer of making unauthorized changes to the document, with the intent of creating a sense that global warming was more certain than it was. The following year, Frederick Seitz, chairman of the George C Marshall Institute, repeated the charges in the Wall Street Journal in an op-ed piece headlined "A Major Deception on Global Warming".
Had Santer made unauthorized changes to the IPCC report? No: his changes were made in response to peer review. He was doing what every scientist is expected to do - and what IPCC rules required him to do - accepting criticism and using it so that the conclusions of the study were rigorous and clear. Frederick Seitz was a former president of the National Academy of Sciences, so it was not plausible that he did not know about the peer-review process.
In 2007, the claims were repeated in Unstoppable Global Warming: Every 1,500 Years, a book whose premise is that "human-emitted CO2 has played only a minor role" in contributing to global warming. The authors are Dennis Avery and Fred Singer. Singer is a physicist with a track record of challenging scientific evidence. He had taken part in the previous attack on Santer.
Both the IPCC and Santer's co-authors took considerable pains to set the record straight, denying that Santer had done anything wrong. Yet, in their book, Avery and Singer reassert that "scientific reviewers discovered that major changes had been made 'in the back room' after they had signed off on the science chapter's contents" and that "Santer single-handedly reversed the 'climate science' of the whole IPCC report". The idea that any one individual could reverse the entire IPCC process is absurd, and yet, like the "Revelle changed his mind" claim, it remains on the Internet today.
Climate scientists have been subjected to repeated attacks of this kind. In 2005, Congressman Joe Barton of Texas demanded that Professor Michael Mann, director of the Earth System Science Centre at Pennsylvania State University, produce a huge volume of paperwork relating to his research. In February, Senator James Inhofe of Oklahoma accused a dozen climate scientists of criminal violations of Federal Law, based on alleged evidence contained in the UEA emails. Recently, Virginia's attorney general, Ken Cuccinelli, went after Mann again, asking that the University of Virginia produce thousands of pages of documents relating to Mann's research.
We, too, have been objects of attack. When one of us (Naomi Oreskes) published a review on the book The Republican War on Science in the journal Science, in which we noted some connections not pursued in that book, Science was threatened with a lawsuit unless it published a rebuttal. (We supplied documents, Science held firm, and the threat went away.)
Blaming scientists for speaking truth to power is an old story. Scientists have long recognized that both the government and public can be reluctant to accept scientific evidence that results in discomfiting conclusions. In 1949, when the USSR detonated its first atomic bomb, the US had to face the reality that it had lost its monopoly on nuclear weapons. Scientists had been warning of this since 1945, but the success of their predictions did not increase their standing. When they then said that any attempt to stay ahead of the Soviets by building the H-bomb would only speed up the arms race, they were accused of being disloyal. As Harold Urey, who won the Nobel Prize in Chemistry in 1934, wrote: "Because we [scientists] told disagreeable truths, we have even been accused of wishing to give up our progress because we are impractical dreamers or plain traitors."
What is most disagreeable to many "resistors" of global warming is the fear of climate change being used as a warrant for heavy-handed government intervention. There is a parallel with 1949: fear of the Soviet Union then was not fear of a potential invasion, but that the Soviets would export communism to Europe, from where it might spread to the US.
Today, US conservatives and right-wing commentators are red-baiting once again. The columnist Charles Krauthammer alleges that "with socialism dead . . . the left was adrift until it struck upon a brilliant gambit: metamorphosis from red to green". Patrick J Michaels, director of the Center for the Study of Science at the Cato Institute, labeled plans for a cap-and-trade system to control greenhouse gases as "Obamunism". The irony is that in 1990, Bush installed a cap-and-trade regime to reduce acid rain because it was an acceptable market-based mechanism. Yet, when Congress finally took the model seriously, conservatives called it communism by other means.
Attacks on climate science, including the 2009 "Climategate" campaign, had nothing to do with the science itself and neither did the entire earlier history of global-warming denial we have studied. Scientists are an easy target. The real issue is the politics of defending the free market.
Since the mid-1990s, the fossil-fuel industry has made common cause with old cold warriors, maverick scientists and conservative think tanks to undermine climate science. The obvious reason is that climate change is what Nicholas Stern calls "the greatest and widest-ranging market failure ever seen." If the free market has failed, then governments will need to act. And that is precisely what various constituencies, from Inhofe to Cuccinelli and a host of think tanks, do not want. It was also what Seitz and his colleagues didn't want. These scientists were passionately anti-communist and viewed any form of government regulation as a step towards socialism.
No wonder we see the rise of McCarthyite tactics today: the stakes, at least in some people's eyes, are the same. But what these people seem to have forgotten from the 1950s is that McCarthyism didn't just destroy the careers of many innocent people: in the end, it destroyed Joe McCarthy.