The number of tweets containing racist, misogynistic and homophobic views rises sharply when temperatures become more extreme, a study has found.
Researchers analysed 4 billion geo-located tweets in the US and recorded a 22 per cent increase in hateful tweets when temperatures rose above 42C.
A rise in hateful tweets also occurs when the temperature falls, but to a smaller degree, with scientists recording a 12 per cent rise in volume when temperatures fell below 13C.
The study by The Lancet Planetary Health said the results point towards “limitations in the ability of humans to adapt to temperature extremes”.
“We provide empirical evidence that hot and cold temperatures can aggravate aggressive tendencies online,” the authors wrote.
It found that the prevalence of hate tweets was at its lowest between temperatures of 15C and 18C. However, the number of tweets would increase “sharply” during temperatures warmers than 27C and colder than 6C.
The researchers examined the link between climate and human aggression, an idea that “dates back to the ancient world”, but has become “more prominent than ever” as climate change continues to cause extreme weather conditions across the world.
“Online hate is a prevalent problem, with four of 10 Americans having personally experienced online harassment and, and disproportionately affects groups that already have an increased risk of marginalisation,” the study authors wrote.
The researchers, from the Potsdam Institute for Climate Impact Research in Germany, used machine learning to identify hate speech in a dataset of around 4bn geo-located tweets from 773 cities across the US over a period of six years.
They then compared the changes in volumes of daily hate tweets against local temperatures.
The limitations of the study included the geo-location of the Twitter users in the dataset, as it could not be assumed that they “necessarily represent all Twitter users”, the researchers acknowledged.
They also acknowledged that the analysis was only conducted on tweets posted in English, and did not take into account the linguistic plurality of the US.
Additionally, the high number of bot accounts existing on the social media platform are estimated to contribute up to 10 per cent of hateful content in some datasets, which “might further bias our data”, the researchers said.
The strength of the link between extreme temperatures and higher volumes of hate tweets highlight the importance of climate change mitigation as well as the need to combat hate speech online, they added.
Large swathes of the US have experienced intense heatwaves and abnormally high temperatures this year. Last week, the extreme weather led to at least 20 potential heat-related deaths.
The US National Weather Service published data last month that revealed extreme heat is becoming a more urgent problem as it has become more deadly than any other extreme weather in the country.
Elsewhere in the world, the UK and parts of Western Europe also saw temperatures soar this summer, with temperatures rising above 40C for the first time in the UK in July and drought declared in some areas of the country.
Scientists have said the ongoing climate crisis made the UK’s record-breaking heatwave this year at least 10 times more likely, and warned that heatwaves will be longer, hotter and more frequent throughout the world as global warming continues.