A massive study of more than a billion social media posts across 157 countries has revealed that extreme temperatures consistently lower people’s moods. Once daily highs move past 35°C, emotional tone becomes noticeably more negative. The strongest effects were recorded in low‑income regions, where residents showed three times the shift seen in wealthier countries. MIT researchers and their partners matched daily sentiment scores from online platforms with local climate data to arrive at these findings.
Heat’s Influence on Behaviour
Links between hot conditions and human behaviour go back decades. Observations show that drivers in heat honk their horns more quickly, reporters produce harsher coverage during heatwaves, and violent crime rises on hotter days. Greek crime statistics linked many murders to warm periods, while historical analysis revealed that riots and uprisings often flared during peak summer. Higher risks of self‑harm have also been associated with extreme heat. Biologists point to possible causes such as lowered serotonin levels or hormone surges, while social scientists stress that economic and infrastructural challenges worsen the impact.
Implications for the Future
Climate projections suggest global positivity could decline by roughly 2.3 percent by the end of the century if temperatures continue to rise. Because vulnerable groups such as older adults and children appear less frequently on social media, the real emotional impact may be more severe. Researchers argue that governments and communities should treat heat as both a physical and emotional hazard, investing not only in cooling infrastructure but also in psychological resilience for populations under growing thermal stress.
