The Science of Climate Change Skepticism

Why you should care

Because personal experiences don’t always reflect global phenomena.

In proposing to slash funding for programs that address climate change, President Donald J. Trump is echoing the views of many conservative voters — and giving voice to a large constituency of climate change skeptics. Why does such skepticism abound, despite overwhelming scientific evidence of global warming? Recent research suggests one possible explanation:

Your beliefs about climate change depend partly on the weather where you live.

Climate describes weather patterns over time; as a common metaphor in climate science goes, “Weather is your mood, and climate is your personality.” While climate change — specifically global warming, a long-term increase in temperatures around the world — has been well-documented, the weather outside people’s front doors plays a bigger role in determining if they believe in the phenomenon. In a study published in the Proceedings of the National Academy of Sciences, researchers found that people in parts of the country that have experienced more record-low temperatures than record highs since 2005 were less likely to believe in climate change.

The study’s lead author, Robert Kaufmann of Boston University, wanted to “really convince people of climate change.” He decided to use a framework most people understand: a bet. “The bet is that for every record all-time-high temperature, you pay me a buck. For every record-low temperature, I pay you a dollar. If the climate is not changing, the bet will be a wash … If the climate really is warming, then I’ll win.”

Sure enough, a 2009 study had found that over the past decade, record-high days outnumbered record-low days 2-to-1. Kaufmann’s lab developed TMax, a measure of record-high and -low days based on data from local weather stations. Specifically, for each day in a calendar year, TMax evaluates which happened more recently — the most recent record high, or the most recent record low. The higher the TMax value, the greater the number of recent record highs compared with recent record lows. In an unchanging climate, there would be 2.5 percent likelihood that a weather station would show a very high TMax value and a 2.5 percent likelihood that it would show a very low TMax value. Instead, 49 percent of weather stations showed very high TMax values, and around 10 percent showed very low TMax values — in other words, greater than expected by random chance.

When Kaufmann saw the TMax data mapped out, he had an aha­ moment: “This looks like maps I’ve seen of people who do and don’t believe in climate change.” He and his lab compared their map to one generated by study co-author Peter Howe at the University of Utah, based on how 12,000 people across the nation responded to the question “Is global warming happening?” In counties where record lows outnumbered record highs — clustered in the middle of the U.S. — a smaller percentage of people believed in global warming. Even recent record highs (after 2005) did little to change beliefs in these counties. “Once they’ve made up their minds, people are good at ignoring evidence … that contradicts their understanding,” Kaufmann says.

To be sure, local temperatures seemed to have a modest effect on beliefs, nudging the proportion of people in a county who believe in global warming by only a few percentage points, says Stephan Lewandowsky of the University of Bristol. But, he clarifies, “that doesn’t mean this is trivial.” Other factors, such as political views, may simply play a bigger role. Indeed, 95 percent of liberal Democrats believe global warming is happening versus only 47 percent of conservative Republicans, according to a Yale and George Mason University survey.

Kaufmann hopes the findings spur climate scientists to rethink how they communicate their findings to the public. While annual reports on global temperature might convince scientists, most people rely on experience. Instead, researchers should cite how much money someone would lose if they had bet against climate change in a given year. If climate change is happening, those who bet against climate change would lose money —and people feel losses more strongly than gains, Kaufmann says.

Patrick Egan of New York University suggests explaining the difference between weather and climate, and relating it back to climate change. “The weather we are experiencing at any given time is a very poor indicator of long-term changes in our climate. In a sense,” he says, “it is a distraction from the very serious problem and challenge of climate change.”

An earlier version of this story misstated Patrick Egan’s first name.

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