A continued rise in global warming could lower the world’s emotional well-being by 2.3% by the end of the century, according to new research that links daily weather extremes with shifts in public mood.

The study suggests climate change threatens people’s everyday psychological experience, not just their physical health and economic security.

Researchers from the Chinese Academy of Sciences and the Massachusetts Institute of Technology, working with colleagues in the United States, analysed 1.2 billion publicly available social media posts made in 2019 across 157 countries.

Using language analysis to gauge sentiment, they matched posts with local weather data to measure how temperatures influence expressions of positive and negative emotion.

The team found that daily maximum temperatures above 35°C were consistently associated with a deterioration in emotional well-being.

While modest warming could slightly lift sentiment in cooler regions, the net global effect of more frequent heat extremes was negative — and fell unevenly across the world.

People in poorer countries were hit disproportionately hard. The researchers estimate that the emotional toll of high temperatures was almost three times greater in low- and middle-income countries than in richer nations.

They attribute the gap to factors such as higher exposure to outdoor heat, more precarious livelihoods, limited access to cooling and healthcare, and infrastructure that is less able to cushion climate shocks.

Projecting today’s observed relationships into the future with mainstream climate scenarios — while allowing for some degree of adaptation — the authors calculate a 2.3% decline in global emotional well-being by 2100 driven by high temperatures alone.

They caution that this is a long-range estimate, yet argue it highlights an often overlooked cost of a warming climate.

The findings, published in the journal One Earth, add to a growing body of evidence that extreme heat worsens mood and mental health outcomes.

The researchers say their approach, which leverages large-scale digital traces to capture day-to-day emotional responses, complements traditional surveys and clinical data by revealing near-real-time changes in public sentiment as weather conditions shift.

Public health experts say the results strengthen the case for targeted heat-risk strategies, especially in countries facing the steepest impacts.

Measures cited include better urban design to reduce heat islands, expanding access to shade, clean water and affordable cooling, heat-health warning systems, flexible work hours for outdoor labour, and social protection for vulnerable groups.

The authors also note that cutting greenhouse-gas emissions remains essential to limit the frequency and intensity of dangerous heat days.

While social media analysis has limitations — including uneven internet access and the fact that online expressions do not capture every facet of mental health — the study’s global scope provides rare insight into how climate stress can seep into daily life.

With heat records being broken in many regions, the researchers argue that tracking emotional well-being alongside physical health could help governments assess the full human cost of a warming planet and plan responses accordingly.

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