For the first time, the three-year global average temperature crossed 1.5°C as extreme heat outpaced floods, storms and wildfires in fatalities.
Heatwaves—often called the “silent killers” of climate extremes—were the deadliest climate-related disasters of 2025, surpassing floods, storms and wildfires in loss of life, according to a new annual report from World Weather Attribution (WWA). While 2025 did not eclipse 2024’s temperature record, it ranks among the hottest years ever recorded. Crucially, scientists note that the three-year global temperature average crossed 1.5°C for the first time, underscoring how continued fossil fuel use is pushing societies toward the limits of adaptation.
RELEVANT SUSTAINABLE GOALS
Extremes at Scale: 157 Events, Heat and Floods Most Frequent
WWA identified 157 extreme weather events in 2025 that met humanitarian impact criteria. Floods and heatwaves were the most frequent (49 each), followed by storms, wildfires and droughts. Of 22 events studied in depth, 17 were found to have been made more severe or more likely by climate change. Researchers also revisited six major heatwaves from previous years to assess how risks have evolved since the Paris Agreement.
Human-induced climate change has made extreme heat both more intense and far more frequent since 2015. Global temperatures have risen by about 0.3°C over that period, adding an average of 11 extra extremely hot days each year worldwide. In many places, comparable mortality data are missing—especially across the Global South—masking the full scale of heat-related deaths.
In Europe, one study estimated 24,400 deaths from a single summer heatwave (June–August) across 854 citiesrepresenting nearly 30% of the continent’s population. Elsewhere, the most vulnerable—poor and marginalised communities lacking reliable cooling, water and resilient housing—suffered disproportionate harm.
Why Heat Killed More: Intensity, Frequency and Inequality
WWA’s analysis across regions—from South Sudan and Burkina Faso to Norway, Mexico, Argentina and England—found climate change intensified 2025 heatwaves. In South Sudan, human-induced warming made a February heatwave about 4°C hotter and turned what was once exceptional into an event expected every other year. Impacts cascaded: schools closed nationwide for two weeks after dozens of children collapsed from heatstroke; residents were urged to stay indoors and hydrate—a huge challenge where homes often feature iron roofs, and many lack cooling, electricity and clean water. In Juba, around one-third of residents lack water access, and only 1% of the city provides green space and shade.
WWA also found that women bear disproportionate risks, concentrated in informal, heat-exposed work such as agriculture and street vending and shouldering unpaid care like cooking and water collection during extreme temperatures—exposures linked to long-term cardiovascular and kidney damage.
Rising global temperatures also intensified storms and floods in 2025, leading to thousands of deaths and millions displaced. WWA concluded climate change increased both the likelihood and severity of extreme rainfall in many events studied. In Asia, a series of powerful storms killed more than 1,700 people and caused billions of dollars in damage, with rainfall made significantly heavier by human-induced warming. In the Caribbean, Hurricane Melissadevastated Jamaica and neighbouring islands, with WWA finding climate change intensified rainfall linked to the storm. Separate analysis showed climate change made all Atlantic hurricanes in 2025 at least 9 metres per hour (about 14 km/h) stronger, a roughly 10% increase in intensity that research suggests can translate into far larger damage.
Adaptation Saves Lives—But Has Limits
The report stresses that heat-resilient schools, early-warning systems, urban cooling, and low-cost interventions—from shade and passive cooling to adjusted school schedules—can dramatically reduce harm, particularly for children. Yet 2025 also showed that adaptation alone cannot keep pace with escalating extremes. WWA warns climate change is already pushing millions toward the limits of adaptation, notably in small island states and low-income regions, where even strong preparedness cannot avert severe losses as storms and heat intensify.
While the Paris Agreement has helped lower projected warming from roughly 4°C to about 2.6°C if current policies were fully implemented, WWA cautions this still yields a dangerously hot world. The three-year breach of 1.5°Csignals that even cooler natural cycles now deliver extreme heat, shrinking the margin for safe adaptation. As WWA co-founder Friederike Otto noted, “Each year, the risks of climate change become less hypothetical and more brutal reality.”
Lead image courtesy of Kamchatka (image of drought land)
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