Executive summary
A decade after the Paris Agreement was adopted, extreme heat has emerged as one of the clearest and most damaging signals of climate change. World Weather Attribution’s 2025 assessment shows that heat extremes have increased in frequency, intensity and duration across all inhabited continents. Even at current levels of warming, extreme heat is already a major driver of health impacts, productivity losses and infrastructure stress. The analysis makes clear that future heat risks will depend strongly on near-term emissions choices.
What happened
Over the ten years since the Paris Agreement was signed in 2015, the world has experienced a steady increase in extreme heat events. By 2025, record-breaking heatwaves had affected regions including Europe, Asia, Africa, the Americas and parts of the Arctic, often occurring earlier in the year and lasting longer than in the past.
These heat events resulted in excess mortality, increased hospital admissions, reduced labour productivity, agricultural losses and strain on power systems. In many regions, heat that would previously have been considered exceptional is now occurring regularly.
What the attribution analysis found
World Weather Attribution finds that human-caused climate change is the dominant driver of the observed increase in extreme heat. Rising global temperatures have shifted the entire temperature distribution, making extreme heat events both more likely and more intense.
The analysis shows that many recent heatwaves would have been extremely unlikely, or effectively impossible, in a pre-industrial climate. Small increases in global average temperature have translated into large increases in the frequency of very hot days and nights.
Attribution studies over the past decade consistently demonstrate that heat extremes respond rapidly and predictably to warming, making heat one of the most robustly attributed climate hazards.
Looking ahead under different warming pathways
The report highlights that future heat risk is highly sensitive to emissions trajectories. Under scenarios consistent with limiting warming to 1.5 °C, further increases in extreme heat are reduced but not eliminated. Under higher-emissions pathways, extreme heat becomes substantially more frequent and severe, with serious implications for habitability in some regions.
The findings reinforce that mitigation and adaptation must proceed in parallel: reducing emissions limits future heat escalation, while adaptation addresses impacts already locked in.
How climate attribution fits into heat risk reporting
Climate attribution provides a clear link between global emissions and local heat impacts. For heat, attribution is particularly powerful because the signal of climate change is strong and uncertainties are relatively low compared with other hazards.
This makes attribution evidence directly relevant for public health planning, infrastructure design and occupational safety standards.
Why this matters for organisations
For employers, infrastructure operators, insurers and public authorities, extreme heat is already a material operational and financial risk. Heat affects workforce safety, asset performance, energy demand and service continuity, with costs rising rapidly as thresholds are exceeded.
Relying on historical temperature norms increasingly underestimates both current and future heat exposure.
How to use this in your own risk work
Organisations should incorporate climate-adjusted heat thresholds into risk assessments, update heat-health and occupational safety plans, and stress-test assets and operations against more frequent and intense heat. Linking near-term adaptation planning with longer-term emissions reduction strategies is essential to limit future risk escalation.
Source
World Weather Attribution (2025). Ten Years of the Paris Agreement: The Present and Future of Extreme Heat.
https://www.worldweatherattribution.org/ten-years-of-the-paris-agreement-the-present-and-future-of-extreme-heat/