Earlier this month Stephen Hawking declared: “We are close to the tipping point where global warming becomes irreversible. Trump’s action [withdrawing from the Paris climate accord] could push the Earth over the brink, to become like Venus, with a temperature of two hundred and fifty degrees [Celsius], and raining sulphuric acid.”

Let’s unpack this a bit, using actual science. The proportion of carbon dioxide in the earth’s atmosphere is currently about 400 parts per million (ppm). The Cambrian explosion—when most animal lineages first appeared—occurred a little more than 500 million years ago when, according to all estimates, carbon dioxide levels were several times higher than today. The atmosphere of Venus is 965,000 ppm carbon dioxide, enveloped in clouds of sulfuric acid. And Venus itself is almost 26 million miles closer to the sun than Earth.

So Hawking’s claim that the earth is on the “brink” of becoming like Venus is preposterous. Even the Intergovernmental Panel on Climate Change explicitly notes that the Earth will not experience a runaway greenhouse effect such as might have occurred on Venus.

What is really disturbing, though, is that Hawking has flagrantly given up on even the pretense of engaging with actual science. He speaks entirely from authority: I am a scientist. Adopt this political policy that I favor or suffer fire and sulfuric acid. The threatened punishment for noncompliance substitutes sulfuric acid for the regular sulfur (brimstone) that features in old-fashioned religion. As far as the justification for the claim, there is no important difference between this and a religious statement that is supposed to be believed simply because it issues forth from a high priest.

***

The philosophy of Dadaism was that something is art if an artist says it is. In 1917 the Dadaist Marcel Duchamp famously proclaimed a urinal to be art. The original urinal was thrown in the trash after being exhibited, but Duchamp later commissioned several replicas, one of which sold for $1,185,000 in 2002. We can leave the merits of Dadaist art to the art critics. It is clear, however, that applying the Dadaist philosophy to science is a big mistake because it means rejecting the commitments that made science successful in the first place.

Something is science because it emerges from an investigation adhering to certain methodological principles. A scientist is someone who faithfully carries out such an investigation. The ability to speak as a scientist is entirely contingent upon one’s ongoing commitment to scientific methods. Yet public discourse about controversial issues in the past few years has promoted a misguided, Dadaist view of what science is.

Consider the physicist and aggressive science promoter Lawrence Krauss. Krauss has received a great deal of funding from the billionaire, and now registered sex offender, Jeffrey Epstein. This last detail is important.

Epstein pled guilty to paying girls as young as 14 for sex, and was suspected of even worse crimes involving underage girls. After he went to prison, Krauss offered the following analysis of his patron: “As a scientist I always judge things on empirical evidence and he always has women ages 19 to 23 around him, but I’ve never seen anything else, so as a scientist, my presumption is that whatever the problems were I would believe him over other people.”

Got that? “As a scientist,” Krauss did not personally witness the crimes, ergo they didn’t happen. After all, if Epstein really was a sex offender, he would walk around in public surrounded by 14-year-old girls, right? Obviously, this is insane. But what’s interesting is that Krauss defended Epstein by invoking his status as a “scientist,” and his commitment to “empirical evidence.” It’s more Dadaist science: I am a “scientist,” therefore whatever I say, no matter how transparently self-serving and nonsensical, is “science.”

But let’s jump back to global warming. The intense debate about the exact percentage of climate scientists who believe in catastrophic climate change is predicated on Dadaist science. Peter T. Doran and Maggie Kendall Zimmerman introduced the famous “consensus-of-97 percent” figure in 2009. They contacted 10,257 earth scientists from a database listing faculty and researchers at academic institutions and U.S. federal facilities; 3,146 people responded, giving their answers to two questions: (1) Compared to the pre-1800s, have mean global temperatures “risen, fallen, or remained relatively constant?” and “Do you think human activity is a significant contributing factor in changing mean global temperatures?”

Ninety percent of respondents answered “risen” to the first question and 82 percent answered “yes” to the second. (Note that the survey didn’t ask whether the warming was a bad thing, which is actually the most important question. But that’s a separate issue.) Doran and Zimmerman then looked at only those respondents who indicated that climate science was their area of expertise and said that more than 50 percent of their peer-reviewed papers in the previous five years were about climate change. This subgroup contained just 79 people. Of these 79, 76 (96.2 percent) said the earth’s temperature had “risen” since the pre-1800s and 75 (97.4 percent of the 77 who answered this question) said “yes,” human activity is a significant contributing factor.

Which led Doran and Zimmerman to conclude: “It seems that the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes. The challenge, rather, appears to be how to effectively communicate this fact to policy makers and to [the] public....”

In this survey, there was no pretense of engaging with reasons and argument. Doran and Zimmerman note that only 64 percent (23 of 36) of their respondents who listed “meteorology” as their area of expertise answered yes to the second question. Meteorology is, of course, the science devoted to studying the atmosphere and weather. You might say that weather is not the same thing as climate. Fair enough. But still, do the skeptical meteorologists have reasons for their opinion? What about the nearly one-fifth of earth scientists in the survey who were skeptical? To the Dadaist scientist, none of that matters. As long as the right authorities make the correct pronouncement, there is no need for investigation.

***

From 2004 to 2009, the U.S. government spent between $7 billion and $8 billion per year on climate-change research. Out of the 79 scientists in Doran and Zimmerman’s survey who said that more than 50 percent of their peer-reviewed publications in the previous five years concerned climate change, how many were receiving a share of this money? The survey was anonymous so we can’t check, but it’s reasonable to suspect that it might have been quite a few of them. At least.

And consider how multiple scientists (not only Krauss) who received cash from Jeffrey Epstein were willing to defend him even after he went to prison. (The eminent evolutionary biologist Robert Trivers, who received around $40,000 from Epstein, didn’t go Krauss’s route of denying the charges. He rationalized the crimes, saying, “By the time [girls are] 14 or 15, they’re like grown women were 60 years ago, so I don’t see these acts as so heinous.”) If anything, maybe earth scientists who don’t receive funding that allows them to publish on climate change should be surveyed about their views, for the same reason we wouldn’t ask Krauss to serve on Epstein’s jury.

***

The idea that the opinion of experts in a narrow academic subfield reliably tracks the truth flies in the face of historical experience.

Consider, for example, the history of psychology. For three or four decades in the middle of the twentieth century, American psychology was dominated by behaviorism. According to behaviorism, animals are born without any behavioral predispositions except a tendency to find certain stimuli reinforcing or punishing. Konrad Lorenz noted that ethologists who observe animals in their natural habitat always knew that behaviorism was untenable. You have merely to witness an animal being born and commencing a suite of complex, unlearned behaviors to see that not all behavior is conditioned.

But behaviorists never bothered to look at animals in the wild. They conducted laboratory experiments, very often involving rats or pigeons pushing levers for food rewards, that simply didn’t trigger the innate responses that manifest under natural conditions. For two generations behaviorists controlled the grants, the journals, the textbooks, and the jobs. Just about everyone who didn’t get on board with them was excluded from the field of psychology. Finally, in the mid-1950s, after many lost years, cognitive scientists managed to gain a foothold in the academy and they eventually overturned the behaviorist consensus.

The history of psychology undermines the philosophy of Dadaist science because it shows how a group of experts can band together on one side of a controversy and end up being wrong. It shows that an apparent consensus in a scientific field does not always arise from the independent judgment of those acquainted with the evidence. Sometimes “consensus” is maintained by the enforcement of orthodoxy by those doling out the jobs, perks, and money.

The debate about catastrophic global warming will ultimately be settled by experts, but it will be by means of argument, not by votes or assertions of authority.