1. SKEPTICISM BAD. Rejecting the scientific consensus of climate change cedes politics to corporate lobbying.

In evaluating a scientific claim that has social, political, or personal consequences there is one more question that needs to be considered: What are the stakes of being wrong in either direction? What is the risk of accepting a claim that turns out to be false versus the risk of rejecting a claim that turns out to be true?

Knowing there is a risk of depression, if a healthy woman decides to take the Pill she can quickly stop taking it if the risk materializes. Pill-induced depression generally clears up quickly, so for many women the risk is modest and worth taking. Similarly, dental floss is cheap and only takes a few minutes a day to use. If it turns out to have little benefit, little has been lost. But some issues are not so easily resolved.

Consider anthropogenic climate change. Despite fifty years of sustained scientific work, communicated in tens of thousands of peer-reviewed scientific papers and many hundreds of governmental and nongovernmental reports, many people in the United States are still skeptical of the reality of climate change and the human role in it. The president has doubted it, as have members of Congress, business leaders, and the editorial page of the Wall Street Journal. Rejecting centuries of well-established physical theory and reams of empirical evidence regarding matters such as sea level rise and the intensification of extreme weather events, others have suggested that while anthropogenic climate change might be a real thing, it is inconsequential and might even be beneficial.191

As a historian of science, mindful of the Limited Energy Theory and eugenics and the history of hormonal contraception—mindful of the difficulties of evaluating dental floss—and above all mindful of the political ideals that geologists brought to bear in evaluating continental drift—I have never assumed that trust in science is always or even usually warranted. I have always felt that it is fair to ask: What is the basis for any scientific claim? Should we trust scientists?

We cannot eliminate the role of trust in science, but scientists should not expect us to accept their claims solely on trust. Scientists must be prepared to explain the basis of their claims and be open to the possibility that they might be wrongly dismissing or discounting evidence. If someone —be it a fellow scientist, an amateur professional, a journalist, or an informed citizen—has a credible case that evidence is being discounted or weighed asymmetrically, this should concern us. Scientists need to remain open to the possibility that they have made a mistake or missed something significant.192 The key point is that the basis for our trust is not in scientists—as wise or upright individuals —but in science as a social process that rigorously vets claims.

This does not mean that scientists must spend time and energy continuing to prove and reprove conclusions that have already been established beyond a reasonable doubt, nor refuting claims that have been refuted. As Thomas Kuhn argued more than half a century ago, to the extent that science can be said to progress, it is because scientists have mechanisms by which they reach agreement and then move on. Perhaps the most salient aspect of the continental drift debate is that it was reopened, which occurred when a new generation of scientists developed new lines of pertinent evidence.193

We can reframe this problem in terms of Pascal's Wager. No matter how well-established scientific knowledge is—no matter how strong the expert consensus—there will always be residual uncertainty. For this reason, if our scientific knowledge is being challenged (for whatever reason), we might take a lead from Pascal and ask: What are the relative risks of ignoring scientific claims that turn out to be true versus acting on claims that turn out to be false?194 The risks of not flossing are real, but not inordinate. The risks of not acting on the scientific evidence of climate change are inordinate.195

Admittedly, the advocates of eugenic social policies considered the risks of not implementing eugenic social policies to be extremely high. That, of course, was their interpretation of the scientific evidence. But as we have seen, there was no consensus on that evidence. So we are back to the importance of consensus. If we can demonstrate that there is no consensus among relevant experts, then it becomes clear that we have a weak basis for public policy. This is the reason why the tobacco industry tried for so long to claim that the science regarding the harms of tobacco was unsettled: if it really had been, then they might have been right to insist that tobacco control was premature.196 Similarly, if there were no scientific consensus about anthropogenic climate change, then the fossil fuel industry and Libertarian think tanks might be right to ask for more research. This is why consensus studies are relevant and important: Knowing there is a consensus does not tell us what to do about a problem like climate change, but it does tell us that we almost certainly have a problem.197

If we can establish that there is a consensus of relevant experts, then what? Can we be confident in accepting their conclusions and using them to make decisions? My answer is a qualified yes. Yes, if the community is working as it ideally should. That is a substantial qualification. As Brian Wynne has put it, if we are to respect and trust science, then "it becomes evident why the quality of its institutional forms—of organization, control and social relations—is not just an optional embellishment of science in public life, but an essential component of critical social and cultural evaluation."198