PARIS: Nearly 3.8 billion people worldwide could be exposed to extreme heat by 2050, and countries across all climate zones remain dangerously unprepared for the scale of adaptation required, scientists warned on Monday.
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Researchers from the University of Oxford said demand for cooling would rise sharply in large tropical countries such as Brazil, Indonesia and Nigeria, where hundreds of millions of people currently lack access to air conditioning or other effective cooling measures. They cautioned that even regions with traditionally cooler climates would face serious challenges as temperatures climb.
The findings, published in the journal Nature Sustainability, analysed multiple global warming scenarios to estimate how frequently people may experience dangerously hot or cold conditions in coming decades. The study projects that the number of people exposed to extreme heat will nearly double by mid-century if global average temperatures rise 2 degrees Celsius above pre-industrial levels.
Lead author Jesus Lizana said the most severe impacts would be felt sooner rather than later, as the world rapidly approaches the 1.5C warming threshold. “The need for adaptation to extreme heat is more urgent than previously understood,” he said, calling for rapid investment in sustainable air conditioning, passive cooling and heat-resilient infrastructure.
Prolonged exposure to extreme heat can overwhelm the body’s natural cooling mechanisms, leading to symptoms ranging from dizziness and heat exhaustion to organ failure and death. Heat-related mortality often occurs gradually, earning extreme heat the label of a “silent killer”.
The study found that developing nations would experience the steepest rise in energy demand for cooling, particularly in South Asia and Southeast Asia. India, Bangladesh and the Philippines were identified among the most affected populations. Several African countries, including Nigeria, South Sudan and the Central African Republic, were projected to see some of the largest increases in dangerously hot days.
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Researchers also warned that wealthier countries such as Canada, Russia and Finland could suffer severe impacts despite limited experience with extreme heat. Scientists stressed that without urgent global action, rising temperatures would disproportionately harm the world’s poorest and most vulnerable communities.