 The scientific method is founded on the principle that evidence determines what is considered factual. We know humans are causing global warming based on multiple lines of objective scientific evidence. This understanding is just as strong as the settled fact that smoking increases the risk of lung cancer. One would think that facts should be considered facts regardless of a person's political persuasion. Unfortunately, people use motivated reasoning when choosing which facts they will accept and which they will deny. For example, a 2013 survey found that only 24% of Republican voters in the United States believe that global warming is being caused by humans. Compare this to 66% of Democratic voters. Political ideology has a big influence on what Americans think about climate science. An education doesn't necessarily remove the influence of political belief. Research by Dan Cahan of Yale University has shown that among political conservatives, a stronger grasp on basic math and science translates to less acceptance of human cause global warming. However, the other research has shown that specific understanding about climate science does translate to higher acceptance of human cause climate change, even among conservatives. Overall, political conservatism is associated with greater rejection of climate science. But let's examine that a little closer. In a 2007 study by Dan Cahan, people organized along four worldviews in order to understand how these shaped understanding of various controversial topics, including global warming. The hierarchical worldview believes that rights, duties, goods, and offices should be distributed based on clearly defined and stable social characteristics like gender, wealth, and what family belong to. At the other end of the scale, the egalitarian worldview believes that rights, duties, goods, and offices should be distributed equally and without regard to such characteristics. The communitarian worldview believes that society's interests should take precedence over individual needs, and that society should look after its individuals. Conversely, the individualistic worldview believes that individuals should look after themselves without collective interference or assistance. The hierarchical and individualistic worldviews are generally associated with conservative beliefs, while egalitarian and communitarian worldviews are associated with liberal beliefs. So why are conservatives more likely to reject climate science? A clue can be found in that same study by Dan Cahan. The researchers provided two versions of a newspaper article that cited a scientific study of global warming. In both versions, the article described a report that found the Earth's temperature is increasing, humans are the cause, and that climate change could have disastrous environmental and economic consequences. However, for one group in the experiment, the newspaper article called for increased anti-pollution regulation. For the other group, the article called for deregulation and revitalization of the nation's nuclear power industry. Conservatives and libertarians who received the nuclear power version were more likely to accept the climate science. When these same groups received the anti-pollution version, they were more likely to reject the science. In fact, the science had a backfire effect. They became even more skeptical about climate change. This was a clear case where individuals subconsciously resisted factual information that didn't fit in with their defining values. In a similar 2014 study by Campbell and Kay in the free market friendly version, a speaker described how the United States could help stop climate change and profit from leading the world in green technology. In the government regulation version of the same speech, the speaker described how the United States could help stop climate change and lead the world in restrictive admission policies. Conservatives reported significantly higher belief in human-caused global warming when the policy solution was the free market friendly version rather than when the policy involved increased governmental regulations. Liberals tended to accept the science in both cases. They didn't really care how the problem is solved as long as it's solved. So it turns out that the political ideology creates a mental block, preventing some people from accepting the scientific evidence for human-caused global warming. The principles of free markets and small governments are important to this worldview. Concerns that reducing the threat of global warming will require government action override factual information. The implications of the science are unacceptable for the ideology, so the science is rejected. People also feel loyalty to certain social groups. If a person feels part of the team human-caused global warming isn't a problem, research has shown that facts alone won't dislodge that belief. Facts can actually reinforce the person's false beliefs. This is known as the worldview backfire effect. However, there are certain gateway pieces of information that are often effective at convincing people across most of the ideological spectrum. For example, when people are aware of the 97% expert consensus on human-caused global warming, they're more likely to accept the scientific evidence. This is true even for more political conservatives. Likewise, when people understand the way the increased greenhouse effect causes the planet to warm, they're more likely to accept the human influence on the climate, regardless of their audiology. Almost no one wakes up in the morning and decides to deny a particular branch of science. People don't just say to themselves, I'm going to reject the scientific consensus on the structure of the atom today. Science denial is always driven by something else, something that has nothing to do with the science. Usually it is something to do with worldview or self-identity. In the case of climate science, the motivating factor is usually political. Some people reject the science because they don't like some of the possible solutions. Facts alone won't change their minds unless we first address their ideological and cultural worldviews. For example, we can emphasize that there are small government free-market solutions to the climate problem, explaining the expert consensus on human-caused global warming and how the greenhouse effect works can also help break through those barriers.