A new global study shows that extremely hot days make people feel more negative, not just physically uncomfortable.
Researchers analyzed 1.2 billion social media posts from platforms like Twitter and Weibo to track how people feel on very hot days.
The study covered 157 countries and 65 languages, showing that this is a worldwide trend, not limited to a specific region.
In countries with lower income levels, people’s moods became 25% more negative during extreme heat (above 35°C or 95°F), compared to just 8% in wealthier countries.
Prof Siqi Zheng from MIT says this study reveals that rising temperatures also damage emotional well-being, not just health or productivity.
Researchers used a powerful AI tool called BERT (Bidirectional Encoder Representations from Transformers) to analyze the sentiment of posts.
Each post was rated from 0.0 (very negative) to 1.0 (very positive), giving a clear picture of how emotions shift with temperature changes.
The posts were connected to 2,988 different locations and matched with local weather data to see how temperature affected mood.
Using World Bank income data, they found that poorer countries suffer triple the emotional impact of extreme heat compared to richer ones.
Dr Wang, one of the authors, says social media gives a live, global snapshot of human emotions, which surveys can’t easily do.
By the year 2100, based on climate models, they expect a 2.3% drop in emotional well-being just from higher temperatures.
Dr Obradovich says as the climate continues to change, society must learn how to cope emotionally with more frequent heat stress.
Since kids and the elderly don’t post much on social media, the study may underestimate the full emotional impact, and these groups are likely even more vulnerable.
The dataset is publicly available, and the researchers hope others will use it to explore more about how climate affects mental health.
Read more at Phys.org. This work is part of the Global Sentiment Project by the MIT Sustainable Urbanization Lab.