Hot weather doesn’t just make people grumpy – it fuels hate speech, if a new study is to be believed.

Researchers at the Potsdam Institute for Climate Impact Research looked at billions of tweets sent between 2014 and 2020, using AI to extract those likely to be hate speech. 

They matched the locations the tweets were sent from with weather conditions at the time, and found when the temperature was in a “feel-good window” of 12C-21C, people were chill. When it got hotter or colder, hate tweets became more common.

When it got above 30C, there were “strong increases in online hate across all climate zones and socioeconomic differences such as income, religious beliefs or political preferences”.

“Even in high-income areas where people can afford air condition[ing] and other heat mitigation options, we observe an increase in hate speech on extremely hot days,” said Anders Levermann, co-author on the study.

“In other words: There is a limit to what people can take. Thus, there are likely limits of adaptation to extreme temperatures and these are lower than those set by our mere physiological limits.”

Current projections for global warming put the rise by 2100 in the region of 1.1C to 5.4C.The research was published this week in The Lancet Planetary Health.