Scientists have linked rising temperatures to falling positivity. A team analysed more than one billion social media posts from 157 nations. They discovered that once temperatures exceed 35°C, emotional tone becomes more negative. Poorer countries showed the steepest shift, experiencing far greater impacts than wealthier areas.
The study, led by MIT and partners, scored posts for sentiment and connected them to local weather data. Results showed that in low-income regions negativity rose by 25%, while in wealthier ones it grew by 8%.
Hot Weather and Behaviour
Evidence of heat affecting behaviour is long-standing. Drivers react more aggressively in hotter conditions, journalists use harsher words, and crime levels often rise with temperature. In Greece, murders were significantly more frequent on days above 25°C. Historic uprisings also clustered in the hottest months of the year. Research has further linked hotter periods to increased suicide risk.
Possible explanations include changes in serotonin or hormone levels that affect mood and aggression. Still, many researchers emphasize that heat acts together with wider social and economic pressures.
What the Future May Bring
Climate models predict that global sentiment could decline by 2.3% by 2100 due to rising temperatures. Since vulnerable groups like children and the elderly are underrepresented online, the true emotional impact may be even larger.
Experts stress the importance of addressing not only the physical dangers of heat but also its hidden psychological consequences.
