A worldwide analysis of over one billion social media posts has shown that people’s moods drop when temperatures rise above 35°C. The decline in positivity was most dramatic in poorer countries, where negative expressions increased far more than in wealthier ones. Researchers from MIT and their collaborators compared the tone of posts on X and Weibo with detailed weather records from 157 nations, finding that communities with fewer resources felt the sharpest emotional impact.
How Heat Alters Human Behaviour
The study builds on earlier research linking hot conditions to irritability and aggression. Experiments revealed that drivers honk more in traffic during heatwaves and journalists use harsher language when the weather is hot. Crime and unrest also tend to climb with temperature. In Greece, murders were far more frequent on days warmer than 25°C. Historical patterns support this as well, with riots and uprisings often breaking out during the hottest months. Some studies also point to increased suicide risk as heat intensifies. Scientists suggest these patterns may stem from chemical shifts in the brain or hormonal changes that foster stress and hostility.
Preparing for a Warming Future
Looking ahead, climate simulation models predict that global optimism could decline by around 2.3 percent by the year 2100. Since children, older adults, and other vulnerable groups are poorly represented on social media, the real impact may be greater than captured in the data. Experts emphasize the importance of planning not just for physical safety during extreme heat but also for the emotional costs it brings, ensuring societies can remain resilient in both body and mind.
