India, Pakistan, Nigeria, and Ghana together host the largest number of cities at risk of extreme heat, according to a new analysis published in the journal Sustainable Cities and Society. The study ranked 205 of the world's largest cities, finding that over 95% of the most at-risk locations are in South and Southeast Asia and Sub-Saharan Africa.
Most At-Risk Cities Identified
Iraq's city of Al Basrah is ranked as the world's most at-risk, followed by Ahmedabad in Gujarat, India. Fourteen Indian cities feature in the top 50 at-risk locations, including Nagpur and Pune in Maharashtra, Madurai and Chennai in Tamil Nadu, Bengaluru in Karnataka, and Kanpur and Lucknow in Uttar Pradesh.
Lead author Nethmi Jayaratne Kariyawasam, a researcher at the University of Oxford, said, "It isn't just exposure to hot temperatures that matters for risk. Our study highlights the importance of multi-faceted global heat risk assessments, which reveal the diverse pathways through which urban heat risk emerges."
Factors Contributing to Risk
The study analyzed cities with a population of over one million. Factors considered include demographic and socioeconomic conditions that increase susceptibility to heat-related illness and mortality, such as age and financial means, as well as access to cooling infrastructure like air conditioning and ecological buffers such as tree cover.
"India, Pakistan, Nigeria and Ghana host the largest number of cities," the authors wrote. Major tourist destinations and international business hubs, including Cairo (Egypt), Bangkok (Thailand), Hanoi (Vietnam), and Jaipur (India), are also ranked in the top 50.
Vulnerability and Coping Capacity
The analytical framework enables a direct comparison of cities both where risk is highest and the processes through which it arises. Hazard exposure alone is not predictive of overall risk, as highly exposed cities such as Bangkok and Jeddah in Saudi Arabia ranked lower due to strong coping capacity.
Vulnerability and coping deficits substantially amplify risk from extreme heat. Consequently, cities with moderate exposure can still rank among the highest at-risk where socio-economic and infrastructural constraints coincide, as seen in Karachi and Faisalabad in Pakistan and Kaduna in Nigeria.
Kariyawasam added, "In many major cities, particularly across Asia and Africa, extreme heat coincides with high vulnerability and limited coping capacity. This combination can substantially increase heat risk and, in some cases, have life-threatening consequences."
Cooling Solutions and Adaptation
Author Radhika Khosla, associate professor at the University of Oxford, who co-supervised the research, said, "Air conditioning demand is increasing worldwide, but many cannot afford it. And if we over-rely on this energy-intensive form of cooling, we risk further global warming in a vicious cycle."
"In order to scale adaptation and thermal comfort for all, we must consider a nuanced approach to keeping people safe, sequencing solutions with passive cooling and low-energy technologies such as fans and coolers being the first step," Khosla said.
The authors concluded, "Overall, this approach offers a scalable foundation for comparative heat risk assessment in cities."
