A recent study has revealed that half of the world’s population—approximately 4 billion people—experienced an extra month of extreme heat due to human-caused climate change between May 2024 and May 2025.
The analysis, conducted by World Weather Attribution, Climate Central, and the Red Cross, found that extreme heat led to illness, deaths, crop losses, and strained energy and healthcare systems. Scientists used peer-reviewed methods to determine how much climate change intensified temperatures and made extreme heat events more likely.
In nearly every country, the number of extreme heat days has at least doubled compared to a world without climate change. Some regions were hit particularly hard—Puerto Rico endured 161 days of extreme heat, whereas only 48 days would have occurred without climate change.
Experts warn that heat waves are silent killers, often misreported as deaths from heart disease or kidney failure. Vulnerable populations, including low-income communities, older adults, and people with medical conditions, suffer the most.
The study underscores the urgent need for early warning systems, heat action plans, and urban planning strategies to mitigate the impact of rising temperatures. Scientists emphasize that the only way to halt the worsening heat crisis is to rapidly phase out fossil fuels.
