05/23/2013 06:15 pm ET Updated Jul 23, 2013

Who Rejects Evidence of Global Climate Change?

Not long ago, I was reading Nate Silver's fascinating book The Signal and the Noise. The book explores ways that people think about data in a number of settings. In one chapter, Silver examines the data relating to global climate change. As he points out, a careful look at the data and related scientific theories makes a few points clear. First, the idea that increases in carbon dioxide (CO2) levels in the air lead to increases in temperature is well-accepted as science (and has been for a long time). The evidence that human activity is causing increases in global levels of CO2 in the atmosphere is also well accepted. The big question is only how quickly global temperatures will rise. As Silver points out, there has been a consistent temperature increase that is significant, though smaller than some of the initial estimates (because of other factors like the amount of sulpher that is also being put into the air by human activity).

The point is, there is scientific consensus about the basic tenets relating to global climate change. Scientists agree that human activity is influencing global temperatures. They disagree only in how quickly it is happening.

Yet, if you scour the internet, you will find a number of websites and blogs out there that are run by climate-change skeptics. These sites suggest (contrary to the scientific consensus) that there is actually widespread disagreement among scientists about climate change, and that there is no compelling evidence that global temperatures are rising.

What kinds of people are prone to reject the scientific evidence for global climate change? This question was explored by Stephan Lewandowsky, Klaus Oberauer, and Gilles Gignac in the May 2013 issue of Psychological Science.

These researchers suggest that people typically engage in motivated reasoning. So, those people who have a reason to want to believe that there is no human created climate change will find reasons not to believe in it. For example, those who believe strongly in unregulated free market economies would be opposed to regulations that would limit CO2 emissions, and so they might have reason to want to be skeptical of evidence for global warming. In addition, those people who are prone to see the operation of conspiracies in large-scale events might also be prone to be skeptical of evidence for climate change.

To explore this question, links to a survey were placed on a number of blog sites that are generally pro-science. The researchers also asked a number of science skeptic bloggers to post links, but they did not participate.

From these links a sample of over 1,100 individuals participated in a survey. The participants were asked a series of questions that gauged people's beliefs about the importance of the free-market compared to the environment (like "The preservation of the free-market system is more important than localized environmental concerns.") They were also asked questions about how likely they were to accept various conspiracy theories (like "The assassination of Martin Luther King was the result of an organized conspiracy by US government agencies such as the FBI and CIA"). Finally, participants were asked questions about their acceptance of climate science as well as their acceptance of other scientific theories (like the fact that HIV causes AIDS).

A number of interesting patterns emerge from the data.

First, believing the free-market is more important than the environment is independent of believing in conspiracies. So, it is not the case that believing in the free-market makes people any more or less likely to accept conspiracy theories.

Second, the more strongly someone believes that the free-market is more important than the environment, the less likely they are to accept scientific conclusions in general and climate science in particular.

Third, the more strongly someone accepts conspiracy theories, the less likely they are to accept scientific conclusions in general and climate science in particular.

This research is important is because it has implications for how to deal with the use of science in public settings. There are many settings in which data should be used to help public policy. For example, vaccines have helped virtually eliminate a number of deadly childhood diseases. There is good scientific evidence for why vaccines work and why they should be mandatory.

Of course, for any public policy, there are some people who reject the policy and the underlying science that led to it.

A natural reaction for those in favor of the policy is to assume that people simply do not understand the science. And so, the obvious response is to describe the science more carefully and in more venues.

If people are engaging in motivated reasoning, however, then just describing the science again in more careful detail is unlikely to change anyone's opinion. Instead, it is important to understand the cluster of beliefs that are leading to the motivated reasoning and to address those instead.

For those people who oppose climate change on the basis of beliefs about the free-market, it would be better to engage in a discussion about the economic costs of rising temperatures. For example, debate could focus on the impact of recent extreme weather patterns on business and agriculture. This debate might help to reduce the strength of the opposition to regulations on pollution, which might then influence people's beliefs about climate change.

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