In a recent lecture, Naomi Oreskes, a distinguished historian of science from the University of California, San Diego, has argued that there is and has been a scientific consensus that human-caused global warming is occurring. She persuasively shows that the sceptical claims about human-caused global warming have not originated from within the scientific community, but rather from politically motivated external actors who, consciously and one would even say cynically, have been artificially manufacturing controversy on the subject.
What are we, however, to make of this claim? On its own, the existence of a scientific consensus does not indicate that the consensus view is correct. Oreskes does have a point about the consensus being initially shared by people of different political views. But it seems that for her – in this lecture at least – politics affect only one side of the debate. Doesn’t it need to be shown that, at least once the climate debate became politicized, similar political influences have not affected the other side as well?
True, Oreskes’ main goal seems to be to demonstrate that there is and has been a consensus. Therefore, the contrarians who say that we should postpone regulation until the science is more settled are wrong, and we should take action. But couldn’t the contrarians just take a step back and point out all the different cases in the history of science in which a scientific consensus was wrong? While not every dissenting scientist is a Galileo, there have been cases in which a scientific consensus was later overturned.
A mere consensus on a scientific theory is neither sufficient nor necessary for its being true. By highlighting the importance of consensus, Oreskes may play into the contrarians’ hands. Moreover, she may convey a distorted image of science to the public that ignores the positive role of scientific pluralism and dissent in justifying our theories and discovering the truth. Lastly, public demand for a scientific unified front as a necessary condition for warranting action may lead to the undesirable consequence of silencing dissenting voices within the scientific community.
If we are to talk about consensus at all rather than the science and the evidence themselves, we should not merely ask whether there is a consensus on a scientific theory. Rather, we should ask whether there is a knowledge-based consensus. A knowledge-based consensus is a consensus that is likely to be justified and true.
We should ask: What properties would we generally expect a knowledge-based consensus to have? In what social conditions would we expect it to emerge?
Allow me to venture some suggestions as to how we might recognize a knowledge-based consensus. One condition is that the agreement must be genuine. Scientists must give the same meaning to the same terms, share the same fundamental background assumptions, etc. Second, when a consensus is socially diverse—shared by men and women, researchers from the private and public sectors, liberals and conservatives—it’s more likely to be knowledge-based. Third, when a consensus is built on an array of evidence that’s drawn from a variety of techniques and methods, it’s less likely to be an accidental by-product of one technique — and all the more likely to be knowledge-based. In my view, when these conditions are present, knowledge is the best explanation for the consensus.
As a philosopher of science, these are the factors that I would like to see the public debate on climate science take into consideration.