New research finds that our response to a projected temperature rise differs depending on the scale we use.

A fresh water lake is formed by the melting of ice on King George Island, Antarctica, on February 1st, 2018. (Photo: Mathilde Bellenger/AFP/Getty Images)

Americans are finally beginning to grasp the profound dangers of climate change. But with many still in denial, it's important to understand the mental blocks that keep us from acknowledging the need for action.

New research pinpoints one unexpected barrier: the Fahrenheit temperature scale.

In a new paper, researchers report the scale's central oddity—freezing happens at 32 degrees, as opposed to the more logical 0 degrees Celsius—makes it more difficult for people to grasp the significance of a projected rise in average temperature.

"Is it possible that a mere change in whether the information presented is in Celsius or Fahrenheit will influence one's perceived concern about climate change?" asks Eugene Chan of Australia's Monash University. "Our results suggest the answer may be yes."

In the Journal of Environmental Psychology, Chen describes two studies that make that case. The first featured 332 American adults. All read a brief statement about the seriousness of climate change, followed by one of four sets of statistics.

They were informed that the average temperature in Antarctica is either minus 24 degrees Celsius, minus 16 degrees Celsius, minus 11 degrees Fahrenheit, or plus 3 degrees Fahrenheit. Then all were told it could rise 9 degrees Fahrenheit (5 degrees Celsius) over the next 500 years.

Afterwards, they were asked how concerned they were about climate change, and how important they felt it was to stop or limit global warming.

"In Celsius, the colder the objective temperature, the greater the perceived impact on climate change," Chan reports. But in Fahrenheit, the opposite was true: Participants expressed more alarm when the current average temperature was plus 3 than when it was minus 11—an odd result, for reasons Chan explains.

"A perceived increase in temperature when it is relatively cold might seem impactful and dangerous," he writes. "But a perceived increase when it is relatively warm might seem less [worrisome], as the Earth is already 'quite warm' and any further increase would have marginal impact."

People who were given the figures in Celsius reacted in that logical way. So why didn't those who were given the same temperatures in Fahrenheit? Chan argues that the key factor is the "reference point" or "anchor" that people use to make sense of a set of numbers.

In attempting to determine relative warmth or coldness, users of Fahrenheit tend to use 32 degrees as the reference point for temperatures above zero, and zero for the temperatures below it. This tendency can muddy our ability to get a true picture of the extent to which one temperature differs from another.

The second study was designed to answer two questions: Does this effect still occur among people who regularly use the Celsius scale? If so, will it affect the amount of money they will give to an environmental organization?

This time, the panel was made up of 43 Americans and 53 Australians (Australia uses the Celsius scale). It was structured similarly to the first, except that, at the end, participants were invited to donate any portion of their $10 payment to Greenpeace for the specific purpose of fighting climate change.

The results replicated those of the first experiment, and there were no significant differences between residents of the two nations. What's more, participants backed up their beliefs with bucks.

Those who were presented with Celsius figures donated more to Greenpeace when they read that the average temperature was minus 11 than when it was 3 degrees. The opposite was true of people who were given the figures in Fahrenheit.

The results suggest that one of the most common warnings conveyed about climate change—that the average temperature of the Earth will rise X degrees in Y years—may not have the desired effect. One also needs to take into account the way our minds read and respond to temperatures.

"For example, a 9 degrees Fahrenheit rise over 100 years may not seem to be a big deal, as [it scans as] a 9 percent difference—nine out of 100," Chan writes. "But an identical 5 degrees Celsius rise in 10 decades might seem more substantial, since it could feel like a 50 percent difference—five out of 10."

To put it simply, our difficulty interpreting figures can make us bad at risk assessment. In this all-important arena, that could have major consequences.

If Ray Bradbury were still with us, perhaps he could helps us grasp this by writing a sequel to his most famous work. It turns out you don't have to hit Fahrenheit 451 for that scale to figure into an apocalyptic future.