Climate Change and Confirmation Bias

A new study suggests that your values, not science, determine your views about climate change.

The more scientifically literate you are, the more certain you are that climate change is either a catastrophe or a hoax, according to a new study [PDF] from the Yale Cultural Cognition Project. 

Many science writers and policy wonks nurse the fond hope that fierce disagreement about issues like climate change is simply the result of a scientifically illiterate American public. If this “public irrationality thesis” were correct, the authors of the Yale study write, “then skepticism about climate change could be traced to poor public comprehension about science” and the solution would be more science education. In fact, their findings suggest more education is unlikely to help build consensus; it may even intensify the debate.

Led by Yale University law professor Dan Kahan, the Cultural Cognition Project has been researching how cultural and ideological commitments shape science policy discourse in the United States. To probe the public’s views on climate change, the Yale researchers conducted a survey of 1,500 Americans in which they asked questions designed to uncover their cultural values, their level of scientific literacy, and what they thought about the risks of climate change.

The group uses a theory of cultural commitments devised by University of California, Berkeley, political scientist Aaron Wildavsky that “holds that individuals can be expected to form perceptions of risk that reflect and reinforce values that they share with others.” The Wildavskyan schema situates Americans’ cultural values on two scales, one that ranges from Individualist to Communitarian and another that goes from Hierarchy to Egalitarian. In general, Hierarchical folks prefer a social order where people have clearly defined roles and lines of authority. Egalitarians want to reduce racial, gender, and income inequalities. Individualists expect people to succeed or fail on their own, while Communitarians believe that society is obligated to take care of everyone.

The researchers report that people whose values are located in Individualist/Hierarchy spaces “can be expected to be skeptical of claims of environmental and technological risks. Such people, according to the theory, intuitively perceive that widespread acceptance of such claims would license restrictions on commerce and industry, forms of behavior that Hierarchical/Individualists value.” On the other hand Egalitarian/Communitarians “tend to be morally suspicious of commerce and industry, which they see as the source of unjust disparities in wealth and power. They therefore find it congenial, the theory posits, to see those forms of behavior as dangerous and thus worthy of restriction.” On this view, then, Egalitarian/Communitarians would be more worried about climate change risks than would be Hierarchical/Individualists.

On a scale in which 1 means no risk and 10 means extreme risk of climate change, the average for the overall sample was a score of 5.7. Hierarchical/Individualists averaged 3.15 points on climate change risk, whereas Egalitarian/Communitarians scored 7.4 on average. The public irrationality thesis predicts that as scientific literacy and numeracy increases the gap between Hierarchical/Individualists and Egalitarian/Communitarians should lessen. Instead, the Yale researchers found that “among Hierarchical/Individualists science/numeracy is negatively (emphasis theirs) correlated with such concern. Hence, cultural polarization actually gets bigger, not smaller as science literacy and numeracy increase.”

Why does polarization increase with scientific literacy? “As ordinary members of the public learn more about science and develop a greater facility with numerical information, they become more skillful in seeking out and making sense of—or if necessary explaining away—empirical evidence relating to their groups’ positions on climate change and other issues,” observe the researchers. Confirmation bias, the tendency to search for or interpret information in a way that confirms one's preconceptions, is ubiquitous.

In addition to climate change risks, the Yale researchers surveyed participants for their views on the safety of nuclear power. In this case, the greater scientific literacy was associated with reduced concerns about the risks of nuclear power for both groups. However, the gap in nuclear power risk perception between Hierarchical/Individualists and Egalitarian/Communitarians expanded rather than converged as scientific literacy increased. In other words, as scientific literacy increased Hierarchical/Individualists became much more comfortable with nuclear power risks than did Egalitarian/Communitarians. Again, everybody suffers from confirmation bias. 

The Yale researchers chalk up this kind of divergence on technological and scientific risks to the pursuit of individual expressive rationality at the expense of collective welfare rationality. Basically, both groups are forming beliefs that advance their personal goals and help them get along with the people they interact with on a daily basis. They illustrate the point by observing, “A Hierarchical Individualist in Oklahoma City who proclaims that he thinks that climate change is a serious and real risk might well be shunned by his coworkers at a local oil refinery; the same might be true for an Egalitarian Communitarian English professor in New York City who reveals to colleagues that she thinks that ‘scientific consensus’ on climate change is a ‘hoax.’”

Kahan and his colleagues then argue that what is individually rational when it comes to expressing cultural values becomes collectively irrational in the pursuit of policies aimed at securing society members' health, safety, and prosperity based on what the best scientific evidence reveals about risk and risk abatement. In addition, the researchers note, beliefs about the risks of climate change “come to bear meanings congenial to some cultural outlooks but hostile to others.” In this case, Egalitarian/Communitarians, who are always eager to rein in what they regard as the unjust excesses of technological progress and commerce, see carbon rationing as an effective tool to achieve that goal. Not surprisingly, Hierarchical/Individualists are highly suspicious when carbon rationing proposals just happen to fit the cultural values and policy preferences of Egalitarian/Communitarians.

The Yale study implicitly accepts the “consensus” that climate change poses substantial dangers to humanity. But what about the cultural values held by climate scientists themselves? Could they be subject to confirmation bias too? A study [PDF] published in 2009 in the journal Climatic Change sheds some light on the policy views of climate scientists. Although the cultural cognition typology is more subtle, the Climatic Change study survey of over 400 climate scientists found that 67 percent identified as liberal, 20 percent moderate, and 13 percent conservative. Around 90 percent agreed that man-made global warming is now happening and that immediate policy decisions need to be made to address it.

According to the survey 96 percent support market incentives to reduce greenhouse gas emissions; 85 percent favor a tax on industry to discourage practices that contribute to global warming; 89 percent favor higher prices for energy supplies and consumer goods that are not environmentally friendly; 99 percent favor developing no-carbon renewable energy supplies like hydro and solar; and 81 percent want to increase the price of fossil fuels. The few conservative climate scientists surveyed were somewhat less eager to adopt these policies except for the ambiguous “use market incentives” policy, which 96 percent favored. However, only 61 percent of politically conservative climate scientists favor a tax on industry; 65 percent support higher energy and consumer products prices; 92 percent back developing renewable fuels; and only 41 percent want to increase the price of fossil fuels. Could it be that Egalitarian/Communitarian biases against industry and commerce are informing the policy prescriptions of climate scientists?

The Pew Research Center conducted a 2009 survey comparing the political ideologies of scientists and the general public. Only 9 percent of scientists identified as conservative, 35 percent as moderate, and 52 percent as liberal, with 14 percent claiming to be very liberal. In contrast, the general public identifies as 37 percent conservative, 38 percent moderate, and 20 percent liberal, and 5 percent very liberal. Slicing the data another way, the survey finds that 81 percent of scientists lean Democrat whereas 52 percent of the general public does. Another telling division between the beliefs of the general public versus scientists is their responses to this statement: "When something is run by the government, it is usually inefficient and wasteful." Fifty-eight percent of scientists disagreed, whereas 57 percent of the public agreed with it.

Kahan and his colleagues at the Cultural Cognition Group suggest the Hierarchical/Individualists discount scientific information about climate change because it is strongly associated with the promotion of carbon rationing as the exclusive policy remedy for the problem. Indeed, it is curious that all of the policy questions in the Climatic Change survey arguably implied policies requiring limits on energy use. Kahan and his colleagues note that other policies that could address climate change might be more acceptable to Hierarchical/Individualists, e.g., deploying more nuclear power plants, geo-engineering, and developing new technologies to adapt to whatever climate change occurs. While the values of Hierarchical/Individualists steer them toward discounting the dangers of climate change, it is also true that the values of Egalitarian/Communitarians push them to discount the dangers that top/down policy interventions pose to the economic well-being of society. Confirmation bias is everywhere. 

Ronald Bailey is Reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books. This column first appeared at

Ronald Bailey is Science Correspondent