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Climate Change Skepticism May Hinge on Personal Experience

CAS prof leads study on people’s belief in global warming

In early 2014, freezing air from the polar vortex at the North Pole swept into the United States. The resulting record cold temperatures and snowfall grounded planes, knocked out power, and caused unusual weather across the country. Even states with normally balmy weather, like Georgia and Louisiana, saw freezing rain and had to declare states of emergency to get through the storms.

But the weather doesn’t have to be that extreme to leave a mark. Scientists have found that experiencing record high or low temperatures affects people’s stated belief in climate change. Their study, published in the Proceedings of the National Academy of Sciences in December 2016, was funded by the Robertson Foundation and the British Academy.

Photo of Robert Kaufmann, BU professor of Earth and environment

BU’s Robert Kaufmann has shown that local high and low temperatures can influence whether people in the United States believe in global warming. Photo by Kalman Zabarsky

The research began when study lead author Robert Kaufmann, a College of Arts & Sciences professor of earth and environment, and PhD candidate Xiaojing Tang (GRS’12,’17) wanted to develop a new measure of local climate change based on record high and low temperatures in the United States. This index, called TMax, rises as the number of recent record high temperatures increases relative to the number of recent record low temperatures. After Tang calculated TMax using data from weather stations across the United States, he showed a map to Kaufmann, who was surprised to see a pattern.

“It clicked in my mind,” says Kaufmann. “It looked like where people do and do not believe in climate change.” Specifically, Tang’s map of TMax resembled maps that climate change researcher and study coauthor Peter Howe, a Utah State University assistant professor of environment and society, had compiled showing the percentage of state and county residents who in 2013 answered yes to the question: “Is global warming happening?”

The climate picture is complicated because the United States is both warming and cooling. If climate in the country remained stable, only about 5 percent of weather stations would, simply by chance, show local warming or cooling. Instead, Kaufmann and his team saw that nearly 50 percent of weather stations had high values for TMax, indicating local warming over time. Unexpectedly, about 10 percent of weather stations showed local cooling, with more frequent recent record cold temperatures. Looking at the map, warming areas are at the coasts, cooling areas in the middle of the country, near the Ohio and Mississippi rivers.

When Kaufmann and his collaborators compared the map of TMax directly to Howe’s, they found a correlation: in counties where recent weather was dominated by record low temperatures, a smaller percentage of people were likely to agree that global warming was happening.

A map of United States counties shows how well Kaufmann’s measure of climate change predicts where people agree that Earth’s climate is warming. In dark red counties, record high temperatures are more recent and predict that people would believe that the globe is warming, and they do. On the other side, dark blue counties show record low temperatures are more recent and predicted people would be skeptical, and, again, that was found to be the case. Image courtesy of the National Academy of Sciences

Why might this be? Study coauthor Jacqueline Liederman, a CAS professor of psychological and brain sciences and director of the BU Cognitive Neurophysiology Lab, believes it’s because humans are prone to learn from their own experiences. What they hear from leading scientists doesn’t dissuade them from what they see for themselves. “We know people have certain biases,” says Liederman. One of these biases is something called “recency weighting,” the tendency for people to assign more value to events that have happened recently, even if they don’t fit a long pattern over time. This was especially true for counties that experienced recent low temperatures. Even if the data showed that record high temperatures were more recent over the past 30 to 50 years, people in counties where there had been many record lows since 2005 were more skeptical of global warming.

Liederman explains that the research also reflected an effect called “confirmation bias.” Essentially, it isn’t easy for anyone to accept information that goes against entrenched beliefs, so conflicting evidence is ignored. The effect of confirmation bias was one-sided in the study, found only in areas where there were recent cold temperatures. If you are more likely to trust your personal experience, and it’s been cold recently, you can discount a rogue record high temperature as just a hot day, rather than evidence of global warming.

Areas with more record low temperatures tended to be in traditionally conservative areas of the country, counties where belief in global warming was already low. Climate change is a politically charged topic in the United States and stark divisions exist along party lines regarding how serious the problem is and what the consequences will be, according to the Pew Research Center. But Kaufmann’s study found that local climate affected people’s willingness to believe in global warming beyond what party affiliation would suggest.

Kaufmann’s group is planning a future project to better determine whether political allegiances affect how people learn from experience. In the meantime, he hopes that what he and his colleagues have learned from this study will help change the way scientists communicate with the public about climate change. “I think climate scientists have to step back and rethink…and use very different sorts of evidence to convince people that climate change is real,” he says.

Caitlin Bird can be reached at cfb14@bu.edu.


6 Comments on Climate Change Skepticism May Hinge on Personal Experience

  • Armando J. Marti on 01.04.2017 at 4:41 pm

    Quite revealing. Excellent work.

  • Jim in New Orleans on 01.04.2017 at 7:37 pm

    It also seems to align with political beliefs. Look at the map- traditional liberal regions are shaded red, while traditional conservative regions are shaded blue or gray. Louisiana has always been a classic poo-pooer of any climate change theory.

  • Dan on 01.05.2017 at 8:18 am

    My beliefs are entrenched because they are correct. If “Global Warming” is real, then how come the only states to embrace real American moral values are colder? Sounds like liberals can’t take a little heat! Sounds like a hoax to me!

    • Jim in New Orleans on 01.06.2017 at 9:12 am

      Dan, your “Us vs. Them” disposition is so counter-productive.

      That said, every bit of legitimate science research indicates that global warming is a reality; of that there is no debate. The legitimate debate is whether or not it is due to man-made causes or due to the natural cycles of the earth. Many climatologists, for example, have observed that many of the same climatic conditions observed in modern times were present before the Ice Age.

    • Hannah on 06.22.2017 at 10:20 am

      You’re being sarcastic, right?

  • Andrew Wolfe on 06.23.2017 at 12:29 pm

    Rather than answering real questions like the validity of mathematics used to combine tens of thousands of variables in which a majority are effectively random, and whether climate science is incorrectly ascribing correlation to causation, we get psychoanalysis. Pretty damned condescending. Not unlike the Soviet Union sending dissenters to mental hospitals.

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