Hurricane Gladys, photographed from orbit by Apollo 7 in 1968 (Photo: NASA)

The range of predicted future warming is enormous — apocalyptism is unwarranted.

The epithet “climate denier,” intended to invoke Holocaust denial, has always been tasteless and inapt. Climate change is not like the Holocaust, nor is questioning the accuracy and predictive power of a scientific model like questioning the historical fact of a genocide that murdered 6 million Jews. But climate activists delighted in defining their opposition this way, with help from prominent figures such as Barack Obama, who in 2014 used Twitter to condemn “climate change deniers” and promote a website, run by Organizing for Action (formerly Obama for America), that featured large black-and-white pictures of then–House speaker John Boehner and Senator Marco Rubio atop a green “Climate Change Deniers” banner. “On climate,” asked the site’s headline, “whose side are you on?”


For a while, this seemed to work. Framing the climate debate as one between noble keepers of the scientific flame and people akin to Nazis gave the former group license to say almost anything. To the casual observer, even the most egregious exaggeration about climate science could seem reasonable compared with its outright rejection. Thus, Obama’s assertion in his 2015 State of the Union address that “no challenge — no challenge — poses a greater threat to future generations than climate change” became widely accepted. When Senator Bernie Sanders warned during a presidential debate that “the scientific community is telling us that if we do not address the global crisis of climate change . . . the planet that we’re going to be leaving our kids and our grandchildren may well not be habitable,” he was not laughed off the stage.

Often, the politicians and pundits targeted with the “denier” label did deserve blame. Ignoring the best available scientific research — an obvious starting point in any other policy debate — was irresponsible or dishonest. Their arguments rarely emerged from any valuable scientific insight, but usually from a fear that acknowledging the scientific basis of climate change would mean accepting radical and costly responses. This was doubly counterproductive: Not only did it grant by default a mainstream foothold to outlandishly overblown climate fears, but also it sidelined and undermined more important and compelling policy-based objections to the activist agenda.


And then a funny thing happened: “Denial” gave way to those more reasoned arguments. Perhaps the accumulation of scientific evidence changed minds. Perhaps it was only the political reality that sank in. Regardless, opponents of aggressive climate policy mostly stopped questioning whether the climate was warming and whether human activity played a role — the two points of agreement that define the famous “97 percent consensus” of climate scientists — and started explaining why that consensus did not justify costly and ineffective policies.

This shift in focus from the basic science of climate change to its public-policy implications has been a disaster for climate activists, exposing the flabbiness at the core of their position. Softened by years of punching down at their opponents’ worst arguments, they became addicted to asserting that “science says so,” and they are now lost when it doesn’t.



When Sanders, back in the Senate, questioned Oklahoma attorney general Scott Pruitt during the latter’s confirmation hearing to lead the Environmental Protection Agency, it was the interrogator who couldn’t keep his facts straight. Pruitt asserted that “the climate is changing, and human activity contributes to that in some manner,” explaining that he had inserted the caveat (“in some manner”) because “the ability to measure, with precision, the degree of human activity’s impact on the climate is subject to more debate.” Pressed by Sanders, he stated again: “The climate is changing, and human activity impacts that.”

Pruitt wanted to discuss “the job of the [EPA] administrator,” which he noted was “to carry out the statutes passed by [Congress].” He also agreed that the “EPA has a very important role at regulating the emission of CO2.” But Sanders was determined to show that Pruitt rejected the scientific consensus, even if this meant falsifying the contents of that consensus.

Framing the climate debate as one between noble keepers of the scientific flame and people akin to Nazis gave the former group license to say almost anything.


Sanders claimed that “97 percent of the scientists who wrote articles in peer-reviewed journals believe that human activity is the fundamental reason we are seeing climate change.” That is wrong. A survey-of-surveys published last year in Environmental Research Letters reported that prior surveys had found 78 percent of scientists agreeing that “the cause of global warming over the past 150 years was mostly human,” 82 percent agreeing that “human activity is a significant contributing factor in changing mean global temperatures,” and 85 percent agreeing that “anthropogenic greenhouse gases are the dominant driver of recent global warming.” Of course, even among those expressing agreement about the “significant” or “dominant” human role, debate would presumably have emerged about whether natural factors accounted for 0, 10, 25, or 50 percent.


Sanders also claimed that “97 percent of scientists who have written articles for peer-reviewed journals have concluded that climate change is real, it is caused by human activity, and it is already causing devastating problems in our country and around the world.” As to the devastating problems, this also is false. He said “the vast majority of scientists are telling us that if we do not get our act together and transform our energy system away from fossil fuel, there is a real question as to the quality of the planet that we are going to be leaving our children and our grandchildren.” Also untrue.

In fact, scientists and economists hold widely varying views on the costs that climate change has caused and will cause. Surveys of scientists rarely address social consequences or policy implications. When President Obama tweeted that “Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous,” even Salon had to acknowledge he was wrong to say “dangerous.” Only half of the economists surveyed by NYU’s Institute for Policy Integrity in 2015 believed “immediate and drastic action is necessary” on climate change; only 56 percent said that “if nothing is done to limit climate change in the future” it would be a “very serious” problem for the United States; only 41 percent believed “climate change is already having a negative effect on the global economy.”

But the New York Times had categorized the Pruitt nomination under the heading climate change denial, albeit without any support. So when Pruitt testified, Times reporter Coral Davenport tweeted, “#Pruitt on #climate: ‘Science tells us climate is changing’ but says extent of human role is up for debate. False.” In her accompanying story, she reported that Pruitt’s views were “not consistent with the scientific consensus” as reflected by the U.N.’s Intergovernmental Panel on Climate Change (IPCC).

Only half of the economists surveyed by NYU’s Institute for Policy Integrity in 2015 believed ‘immediate and drastic action is necessary’ on climate change.

What does the IPCC actually say? While it is “extremely likely that human activities caused more than half of the observed increase in [temperature] from 1951 to 2010,” the attribution for the approximately 0.6°C of warming requires wide ranges that are “likely” to be accurate: between 0.5 and 1.3°C for greenhouse gases, between – 0.6 and + 0.1°C for other human activity, and between – 0.1 and + 0.1°C apiece for natural causes and internal variability. For the slower warming observed during the period from 1998 to 2012, the IPCC could offer only low to medium confidence in its explanation.

So Pruitt’s comments were not “False.” Indeed, in a later story Davenport’s colleague Justin Gillis acknowledged that Pruitt’s position was “almost axiomatically true.” But, Gillis argued, it remained problematic because

anybody who did not know better might come away thinking there is room to doubt whether humans are the main cause of global warming. Mr. Pruitt did not actually say that, of course.. . . Mr. Pruitt and the other Trump nominees labored to avoid overt denial while signaling to their allies that there is enough doubt to justify inaction on emissions or even rolling back steps the Obama administration took.


This is the crux of the matter. Statements about climate change are no longer being policed for their accuracy, but rather for the degree to which they help or harm the activist agenda. The Atlantic explains that “the new climate denial is like the old climate denial” because “both are excuses for inaction.” Why didn’t Sanders ask Pruitt the obvious follow-ups: “Do you see that lack of precision as relevant to the policy choices facing us?” or “Of course, science is always subject to imprecision, but do you believe we should take action to reduce greenhouse-gas emissions?” Sanders didn’t ask these questions because he had no interest in discussing climate policy, where his own ideas make no sense (including, for instance, banning nuclear power and “bringing climate deniers to justice”). His position rests on the fiction that scientists unanimously agree, and that is where he must make his stand.

Pruitt’s emphasis on the difficulty of measuring, “with precision, the degree of human activity’s impact” also crosses a red line for activists, because the precision with which climate models can describe what is happening links directly to the precision with which they can describe what will happen. If scientists do not know exactly how the climate system is behaving now, we might accord less weight to their projections into the distant future.

The precision with which climate models can describe what is happening links directly to the precision with which they can describe what will happen.

Secretary of State Rex Tillerson hit that tripwire in his own confirmation hearing when he said: “The increase in the greenhouse-gas concentrations in the atmosphere are [sic] having an effect; our ability to predict that effect is very limited.” Professor Katharine Hayhoe mocked the claim, suggesting that perhaps it would have been correct in the 1800s. “In 2017? Not so much.” Professor Michael Mann called it “indefensible.” In the Guardian, Dana Nuccitelli concluded, “Functionally [Tillerson] might not be very different than a Secretary of State who outright denies climate change.” Mashable’s Andrew Freedman warned that Tillerson, Pruitt, and fellow Trump nominee Rick Perry had “moved from outright climate denial to a more subtle, insidious and risky form.”


But as the IPCC emphasizes, the range for future projections remains enormous. The central question is “climate sensitivity” — the amount of warming that accompanies a doubling of carbon dioxide in the atmosphere. As of its Fifth Assessment Report in 2013, the IPCC could estimate only that this sensitivity is somewhere between 1.5 and 4.5°C. Nor is science narrowing that range. The 2013 assessment actually widened it on the low end, from a 2.0–4.5°C range in the prior assessment. And remember, for any specific level of warming, forecasts vary widely on the subsequent environmental and economic implications.

At least one might assume that reasonable minds could be allowed to differ on the ultimate question of how well society is likely to cope with the effects of climate change — a political, social, and economic question several degrees removed from anything resembling a scientific consensus. Not so. I addressed these issues in a recent Foreign Affairs essay, in which I called the IPCC “the gold-standard summary,” cited it repeatedly, and adopted its estimate that temperatures could rise by 3 to 4°C this century. My essay further embraced the Obama administration’s “Social Cost of Carbon” analysis and adopted its high-case model for economic cost. But the essay argued that the likely impact of all this was “manageable” rather than “catastrophic.” Mann decried it as “#Koch climate denial propaganda.” Eric Holthaus, meteorologist and host of the podcast Our Warm Regards, called it “a master class in modern climate denial.”

The scope of viewpoints that constitute “denial” is rapidly expanding to swallow all opposition to favored climate policies. In Scientific American, blogger Peter Dykstra declared “grudgingly admitting the problem while scrambling to avoid addressing it” to be a form of climate denial. Writing in Rolling Stone, Bill McKibben pathetically attempted to introduce the term “Renewables Denial” (“at least as ugly and insidious as its twin sister, Climate Denial”) to describe skepticism that wind and solar power can meet the world’s energy needs anytime soon.

At stake are the boundaries of debate in our democratic society, on an issue that the self-appointed enforcers insist is the most important one facing us. The ad hominem “denier” criticism places arguments and their purveyors beyond the pale, unworthy of response. Appealing to a purported “97 percent consensus” asserts that the question has been scientifically answered and policymakers have no business debating it. Such rhetorical techniques are wildly inappropriate where science is in fact, by its own admission, not settled, and especially where science is but one input to a difficult policy question.

Science is but one input to a difficult policy question.

Fortunately, this nonsense is unsustainable. The Times tried letting people speak for themselves, introducing quotes from twelve of Trump’s Cabinet nominees with the summary: “Most of the people President-elect Donald J. Trump has chosen for the top tiers of his administration have expressed doubt that climate change is caused by human activity.” But anyone who actually read the quotes discovered that most of them raised no issues with climate science at all.

In early March, Davenport tried calling Trump appointees “skeptics,” rather than “deniers.” But Gillis summarized her story, headlined “EPA Head Stacks Agency with Climate Change Skeptics,” in a tweet as “Top posts at EPA are being stocked with climate-change denialists.” He then acknowledged that the conflicting word choices were no accident and that the Times “cannot seem to achieve internal consistency about what word to use, despite best efforts.” That was awkward, though not as awkward as Professor Michael Mann’s testimony before the House Science Committee later that month: “I don’t believe I called anybody here a denier,” he asserted, “yet that’s been stated over and over again. So I’ve been misrepresented quite a bit today.” To which Professor Judith Curry, sitting just to his right, responded, “It’s in your written testimony.” Sure enough, on page 6, Mann referred to “climate science denier Judith Curry,” even averring, “I use the term carefully.”

Activists, so eager to bar the gates to the public square and keep their opponents out, have instead locked themselves in. If everyone agrees with the 97 percent consensus, and that consensus does not dictate any particular policy outcome, they have nothing else to say. Perhaps this is for the best. If the extremists from both sides become sufficiently marginalized, a reasoned policy debate might emerge about the real risks of climate change and the cost-effective responses. This would require the media to admit that their “denier” terminology has lost all meaning and to attend equally to the scientifically unsupported statements from both sides.


It would also require a consistent, scientifically accurate message from the White House. The president should clean up the embarrassing ambiguity and vacuity in his own views. And his administration should make clear that it works from mainstream scientific conclusions. EPA Administrator Pruitt confused matters greatly with comments to CNBC last month that went beyond his testimony about “precision” and “debate” and suggested that human activity was not the primary cause of recent warming. Pruitt had no basis for taking that position, nor does he gain anything from it; even Fox News confronted him. Conversely, an accurate statement of the science would only strengthen his position in defending the policies he seeks to implement. The more he focuses discussion on costs and benefits of EPA actions, the more reasonable he will seem — and the more reasonable he will be.

For now, though, navigating the climate debate will require translating the phrase “climate denier” to mean “anyone unsympathetic to the most aggressive activists’ claims.” This apparently includes anyone who acknowledges meaningful uncertainty in climate models, adopts a less-than-catastrophic outlook about the consequences of future warming, or opposes any facet of the activist policy agenda. The activists will be identifiable as the small group continuing to shout “Denier!” The “deniers” will be identifiable as everyone else.

— Oren Cass is a senior fellow at the Manhattan Institute. This article appears in the May 1, 2017, issue of National Review.

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