Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks

The report finds that human-induced climate change significantly increased the frequency and intensity of extreme heat globally from May 2024 to May 2025, affecting billions of people and making all 67 identified significant heat events more likely. It highlights the disproportionate impact on vulnerable populations and the systemic failure to accurately document heat-related mortality, while advocating for a combination of urban heat action plans and aggressive fossil fuel mitigation.

• Between May 1, 2024, and May 1, 2025, approximately 4 billion people, or 49% of the global population, experienced at least 30 additional days of extreme heat—defined as temperatures hotter than 90% of local observations from 1991-2020—due to human-caused climate change.
• Climate change at least doubled the number of extreme heat days in 195 countries and territories when compared to a counterfactual world without human-induced climate change.
• All 67 extreme heat events identified as significant based on record temperatures or major impacts were influenced by climate change. The event with the strongest influence occurred in the Pacific Islands (May 1-30, 2024), where climate change made the event at least 69 times more likely.
• Specific regional heat events were strongly driven by climate change: a March 2025 heat wave in Central Asia was up to 10°C warmer than it would have been without human influence, and a December 2024 event across central and western Africa (from Senegal to South Sudan and the Central African Republic) was made at least 15 times more likely.
• Aruba experienced the highest number of extreme heat days globally during the analysis period, with 187 observed days, compared to 45 days that would have occurred without human-induced climate change.
• Heat-related impacts are chronically underreported, especially in low- and middle-income countries, because deaths are often misattributed to comorbid conditions like renal failure or cardiovascular and pulmonary issues.
• Extreme heat creates cascading effects across sectors, impairing agricultural productivity, straining health systems, disrupting energy infrastructure, and reducing water availability.
• While City Heat Action Plans (HAPs) are being adopted in North America, Europe, Australia, and South Asia, significant gaps in these risk-reduction mechanisms persist in Latin America, the Middle East, Africa, and small island states.

APA

Giguere, J., Otto, F. E. L., Tannenbaum, A., Vahlberg, M., Arrighi, J., Dahl, K., Kimutai, J., Philip, S., Raju, E., Singh, R., & Veitch, A. (2025). Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks. World Weather Attribution. http://www.worldweatherattribution.org/wp-content/uploads/Report_-Climate-Change-and-the-Escalation-of-Global-Extreme-Heat-Heat-Action-Day-2025.pdf

Chicago

Giguere, Joseph, Friederike E. L Otto, Arielle Tannenbaum, Maja Vahlberg, Julie Arrighi, Kristina Dahl, Joyce Kimutai, et al. Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks. World Weather Attribution, 2025. http://www.worldweatherattribution.org/wp-content/uploads/Report_-Climate-Change-and-the-Escalation-of-Global-Extreme-Heat-Heat-Action-Day-2025.pdf.

Wikipedia

{{cite report |last1=Giguere |first1=Joseph |last2=Otto |first2=Friederike E. L |last3=Tannenbaum |first3=Arielle |last4=Vahlberg |first4=Maja |last5=Arrighi |first5=Julie |last6=Dahl |first6=Kristina |last7=Kimutai |first7=Joyce |last8=Philip |first8=Sjoukje |last9=Raju |first9=Emmanuel |display-authors=etal |title=Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks |publisher=World Weather Attribution |date=2025 |url=http://www.worldweatherattribution.org/wp-content/uploads/Report_-Climate-Change-and-the-Escalation-of-Global-Extreme-Heat-Heat-Action-Day-2025.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{giguere2025climate, author = {Giguere, Joseph and Otto, Friederike E. L and Tannenbaum, Arielle and Vahlberg, Maja and Arrighi, Julie and Dahl, Kristina and Kimutai, Joyce and Philip, Sjoukje and Raju, Emmanuel and Singh, Roop and Veitch, Abbie}, title = {{Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks}}, institution = {World Weather Attribution}, year = {2025}, url = {http://www.worldweatherattribution.org/wp-content/uploads/Report_-Climate-Change-and-the-Escalation-of-Global-Extreme-Heat-Heat-Action-Day-2025.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }