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Can a hot day persuade people that global warming is real?

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Weather isn’t the same thing as climate. Just because it’s sunny or chilly on a given day doesn’t tell us all that much about long-term temperature trends. Even so, plenty of research suggests that local weather does heavily influence how people think about climate change. Back in 2009, survey data from Patrick Egan and Megan Mullin found that Americans were more likely to agree that there was “solid evidence” of climate change on hotter-than-average days. And now Justin Wolfers points to a fascinating recent paper with similar findings.

NASA/REUTERS

A NASA drought map from Nov. 28. Blue indicates wetter-than-normal conditions; yellow and red indicate a spectrum of drier-than-average conditions.

MIT’s Tatyana Deryugina found that short-term abnormalities in temperature and precipitation have a sizable influence on whether people believe that “the effects of global warming have already begun to happen.” But that shift is short-lived, lasting just a few days. After a week has passed, the effect of a hot day on climate beliefs seems to vanish

On the other hand, Deryugina also found that prolonged periods of abnormal weather — say, an extended drought of the sort that Texas has been suffering this year — can shift people’s attitudes fairly significantly. (That runs in both directions, though: An extended cold snap can convert the locals into climate skeptics, too.)

It’s always difficult to know exactly how to interpret these results. Perhaps people are just plain irrational and put way too much stock in their local weather. Although, as Deryugina points out, it’s also possible that weather’s effects are more indirect. A protracted drought could prompt more discussion of the scientific evidence for global warming in the local media, for instance, and that might influence opinion.

Meanwhile, Egan and Mullin found that the local weather effect seems to be strongest for people who aren’t particularly politically partisan. Yet for people who identify strongly with one party or the other, the effect is basically nonexistent. Committed Republicans tuning into Rush are unlikely to believe in man-made climate change no matter how sweaty it gets, while ardent Democrats won’t stop listening to Al Gore just because there’s an icy chill on the day he’s testifying before Congress. To get a taste for how powerful partisanship can be: Deryugina’s regressions imply that there would have to be a whopping 30-degree swing in temperature to overcome the effects of being “very conservative.”

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