Support Provided ByLearn More
Planet EarthPlanet Earth

Why Doesn’t Everyone Believe Humans Are Causing Climate Change?

Two scientists, two very different answers to why some people refuse to believe that humans are changing the climate.

ByBrad BalukjianNOVA NextNOVA Next
Smoke billowing out of industrial chimneys.
Despite decades of evidence, most Americans don't believe that humans are causing climate change.

Last week during his tour of Asia, President Barack Obama struck a new global warming deal with China. It was a landmark agreement that many expect could break the logjam that has kept the world’s two largest emitters largely on the sidelines of talks to curb greenhouse gas emissions. Both countries agreed to reduce carbon dioxide emissions, with the U.S. ramping up reductions starting in 2020 and China beginning cuts in 2030.

Yet back home, President Obama still faces an electorate that doesn’t believe climate change is caused by humans. Only 40% of Americans attribute global warming to human activity, according to a recent Pew Research Center poll . This, despite decades of scientific evidence and the fact that Americans generally trust climate scientists .

That apparent cognitive dissonance has vexed two scientists in particular: Michael Ranney, a professor of education at the University of California, Berkeley, and Dan Kahan, a professor of law at Yale University. According to both, we haven’t been asking the right questions. But they disagree on what, exactly, those questions should be. If one or both of them are right, the shift in tone could transform our society’s debate over climate change.

The Wisdom Deficit

In the 1990s, Michael Ranney started informally asking people what they perceived to be the world’s biggest problem. He hadn’t set out to tackle environmental issues—he was first trained in applied physics and materials science before turning to cognitive psychology. But time and again, he heard “climate change” as an answer.

Ranney had also noticed that while the scientific community had converged on a consensus, the general public had not, at least not in the U.S. The Climategate controversy in late 2009 over leaked e-mails between climate scientists and Oklahoma Senator James Inhofe’s insistence that anthropogenic global warming is a hoax are just two examples of the widespread conflict among the American public over what is causing the planet to warm.

Support Provided ByLearn More

Ranney and his team say that a “wisdom deficit” is driving the wedge. Specifically, it’s a lack of understanding of the mechanism of global warming that’s been retarding progress on the issue. “For many Americans, they’re caught between a radio talk show host—of the sort that Rush Limbaugh is—and maybe a professor who just gave them a lecture on global warming. And if you don’t understand the mechanism, then you just have competing authorities, kind of like the Pope and Galileo,” he says. “Mechanism turns out to be a tie-breaker when there’s a contentious issue.”

Despite the fact that the general public has been inundated with scientific facts related to global warming, Ranney says that our climate literacy is still not very high. In other words, though we may hear a lot about climate change, we don’t really understand it. It’s similar to how lots of people follow the ups and downs of the Dow Jones Industrial Average but don’t understand how those fluctuations relate to macroeconomic trends.

Climate illiteracy isn’t just limited to the general public, either. Ranney recalls a scientist’s presentation at a recent conference which said that many university professors teaching global warming barely had a better understanding of its mechanism than the undergraduates they were teaching. “Even one of the most highly-cited climate change communicators in the world didn’t know the mechanism over dinner,” he says.

“If you don’t understand the mechanism, then you just have competing authorities, kind of like the Pope and Galileo.”

One of the most common misconceptions, according to Ranney, is that light energy “bounces” off the surface of the Earth and then is trapped or “bounced back” by greenhouse gases. The correct mechanism is subtly different. Ranney’s research group has boiled it down to 35 words: “Earth transforms sunlight’s visible light energy into infrared light energy, which leaves Earth slowly because it is absorbed by greenhouse gases. When people produce greenhouse gases, energy leaves Earth even more slowly—raising Earth’s temperature.”

When Ranney surveyed 270 visitors to a San Diego park on how global warming works, he found that exactly zero could provide the proper mechanism. In a second experiment, 79 psychology undergraduates at UC Berkeley scored an average of 3.8 out of 9 possible points when tested on mechanistic knowledge of climate change. In a third study, 41 people recruited through Amazon’s Mechanical Turk, an online marketplace for freelance labor, scored an average of 1.9 out of 9. (Study participants in Japan and Germany had a similarly poor showing, meaning it’s not just an American problem.) With every new experiment, Ranney found consistently low levels of knowledge.

At least, he did at first. In his experiments, after the first round of questions, Ranney included a brief lecture or a written explanation on the correct mechanism behind global warming. He then polled the same people to see whether they understood it better and whether they accepted that humans are causing climate change. In the UC Berkeley study, acceptance rose by 5.4%; in the Mechanical Turk study, it increased by 4.7%. Perhaps most notably, acceptance increased among both conservatives and liberals. There was no evidence for political polarization.

That doesn’t mean polarization doesn’t exist. It’s certainly true that liberals are more likely to accept anthropogenic global warming than conservatives. Myriad studies and surveys have found that. But political affiliation doesn’t always overwhelm knowledge when it becomes available—Ranney found no evidence for a difference between conservatives’ and liberals’ change in willingness to accept climate change after his “knowledge intervention.”

Convinced that the key to acceptance is understanding the mechanism, Ranney created a series of no-frills videos of varying lengths in multiple languages explaining just that. More than 130,000 page views later, Ranney is not shy about his aims: “Our goal is to garner 7 billion visitors,” he says.

Depolarizing Language

Meanwhile, Dan Kahan says that it’s not a wisdom gap that’s preventing acceptance of human’s role in climate change, but the cultural politicization of the topic. People don’t need a sophisticated understanding of climate change, he says. “They only need to be able to recognize what the best available scientific evidence signifies as a practical matter: that human-caused global warming is initiating a series of very significant dynamics—melting ice, rising sea levels, flooding, heightened risk of serious diseases, more intense hurricanes and other extreme weather events—that put us in danger.”

According to Kahan, the problem lies in the discourse around the issue. When people are asked about their acceptance of anthropogenic global warming, he says the questions tend to confound what people know with who they are and the cultural groups they identify with. In those circumstances, declaring a position on the issue becomes more a statement of cultural identity than one of scientific understanding.

Kahan’s ideas are based on his own surveys of the American public. In one recent study of 1,769 participants recruited through the public opinion firm YouGov, he assessed people’s “ordinary climate science intelligence” with a series of climate change knowledge questions. He also collected demographic data, including political orientation. Kahan found no correlation between one’s understanding of climate science and his or her acceptance of human-caused climate change. Some people who knew quite a bit on the topic still didn’t accept the premise of anthropogenic climate change, and vice versa. He also found that, as expected, conservatives are less likely to accept that humans are changing the climate.

Declaring a position on the issue can become more a statement of cultural identity than one of scientific understanding.

Unlike Ranney, Kahan did find strong evidence for polarization. The more knowledgeable a conservative, for example, the more likely they are to not accept human-caused global warming. Kahan suggests that these people use their significant analytical skills to seek evidence that aligns with their political orientation.

Still, despite many people’s strong reluctance to accept anthropogenic global warming, cities and counties in places like southeast Florida have gone ahead and supported practices to deal with global warming anyway. Kahan relates one anecdote in which state and local officials in Florida have argued for building a nuclear power generator higher than planned because of sea-level rise and storm surge projections. But if you ask these same people if they believe in climate change, they’ll say, “no, that’s something entirely different!” Kahan says.

Kahan’s not exactly sure why some people act in ways that directly contradict their own beliefs—he laughs and verbally shrugs when asked—but he has some ideas. The leading one is the notion of dualism, when someone mentally separates two apparently conflicting ideas and yet feels no need to reconcile them. This happens on occasion with religious medical doctors, he says, who reject evolution but openly admit to using the principles of evolution in their work life.

Whatever the cause, Kahan thinks the case of southeast Florida is worth studying. There, the community has been able to examine the scientific evidence for climate change and take action despite widespread disagreement on whether humans are actually driving climate change. The key, Kahan says, is that they have kept politics out of the room.

Two Sides of the Same Coin

Ranney and Kahan, much like the skeptics and supporters of human-caused climate change, question the other’s conclusions. Kahan is skeptical that Ranney’s approach can be very effective on a large scale. “I don’t think it makes sense to believe that if you tell people in five-minute lectures about climate science, that it’s going to solve the problem,” he says. He also questions the applicability of Ranney’s experiments, which have mostly included students and Mechanical Turk respondents. “The people who are disagreeing in the world are not college students,” he says. “You’re also not in a position to give every single person a lecture. But if you did, do you think you’d be giving that lecture to them with Rush Limbaugh standing right next to them pointing out they they’re full of shit? Because in the world, that’s what happens.”

Hundreds of millions of in-person lectures would certainly be impossible, but Ranney has high hopes for his online videos. Plus, Ranney points out that Kahan’s studies are correlative, while his are controlled experiments where causation can be more strongly inferred. In addition, most of the measures of climate science knowledge that Kahan uses in his research focus on factual knowledge rather than mechanism. (For example, the multiple choice question, “What gas do most scientists believe causes temperatures in the atmosphere to rise?”). Ranney’s work, on the other hand, is all about mechanism.

Receive emails about upcoming NOVA programs and related content, as well as featured reporting about current events through a science lens.

Despite their apparent disagreement, Ranney thinks the debate is a bit of a false dichotomy. “It’s certainly the case that one’s culture has a significant relationship to whether or not you accept [anthropogenic global warming], but that doesn’t mean your global warming knowledge isn’t also related to it. And it doesn’t mean you can’t overcome a cultural predilection with more information,” Ranney says. “There were a lot of things that were culturally predicted, like thinking we were in a geocentric universe or that smoking was fine for you or that the Earth was flat—all manner of things that eventually science overcame.”

Perhaps Ranney and Kahan are on the same team after all—they would probably agree that, at the end of the day, both knowledge and culture matter, and that we’d be well-served to focus our energy on how to operationally increase acceptance of anthropogenic global warming. “Whatever we can do now will be heroic for our great-grandchildren, and whatever we do not do will be infamous,” Ranney says.

Photo credit: georgeclerk/iStockphoto

Funding for NOVA Next is provided by the Eleanor and Howard Morgan Family Foundation.

Major funding for NOVA is provided by the David H. Koch Fund for Science, the Corporation for Public Broadcasting, and PBS viewers. Additional funding is provided by the NOVA Science Trust.