The world’s heat risk is increasingly being shaped not just by rising temperatures but by inequalities in infrastructure, income and access to cooling, with more than 95% of the highest-risk cities concentrated in South and Southeast Asia and Sub-Saharan Africa.
These are the findings of a new global study from the University of Oxford, which analysed 205 cities with populations of more than a million people to determine where people are most at risk from rising global temperatures.
The paper, published in Sustainable Cities and Societies, examined key indicators of risk across hazard exposure, vulnerability and coping capacity.
In their study, the researchers describe how extreme heat is emerging as one of the most dangerous and inequitable consequences of climate change, with cities increasingly becoming global hotspots of risk as populations grow and urbanisation intensifies.
The analysis found a striking geographical clustering of extreme heat risk. “More than 95% of cities above the 90th percentile risk are concentrated in South and Southeast Asia and Sub-Saharan Africa, where the urban populations are rapidly expanding and resilient systems remain weak,” the researchers wrote.
India, Pakistan, Nigeria and Ghana host the largest number of cities with high-risk scores. Major tourist destinations and international business hubs, including Cairo (Egypt), Bangkok (Thailand), Hanoi (Vietnam) and Jaipur (India), are also ranked in the top 50. The analysis identifies the city of Al Basrah in Iraq as the world’s most at-risk.
“It isn’t just exposure to hot temperatures that matters for risk,” said lead author Nethmi Jayaratne Kariyawasam, of the Oxford Smith School of Enterprise and the Environment.
“Our study highlights the importance of multifaceted global heat risk assessments, which reveal the diverse pathways through which urban heat risk emerges.”
In many major cities, particularly across Asia and Africa, extreme heat coincides with high vulnerability and limited coping capacity, Kariyawasam said. “This combination can substantially increase heat risk and, in some cases, have life-threatening consequences.”
The factors considered include the demographic and socio-economic conditions that increase susceptibility to heat-related illness and mortality, such as age and financial means, as well as access to cooling infrastructure such as air conditioning and ecological buffers such as tree cover.
Cities with similar heat exposure can face radically different risks based on social and infrastructural conditions, according to the study.
“However, heat risk in cities extends beyond climatic extremes and is mediated by social vulnerabilities and infrastructural capacities that determine how populations experience and respond to heat,” wrote the authors.
The pattern is not explained by temperature alone but by how exposure interacts with inequality and infrastructure. A central finding is that extreme heat does not automatically translate into extreme risk.
“While hazard exposure is a critical component of risk, it is not deterministic,” the study said.
Some of the world’s most heat-exposed cities, among them Bangkok and Jeddah, do not rank among the highest-risk cities overall. The researchers attribute this to stronger coping systems, including access to cooling infrastructure and relatively lower energy constraints.
“Their comparatively high coping capacity, including greater urban greening and relatively lower energy costs, offset exposure and reduce their overall risk profile.”
By contrast, other cities face high risk even under moderate heat conditions when vulnerability and infrastructure deficits converge. “Vulnerability and coping deficits substantially amplify risk, such that cities with only moderate exposure can still rank among the highest risk where socio-economic and infrastructural constraints coincide.”
While the research provides a global comparison, the authors caution that city-level averages can obscure severe inequalities within urban areas. “However, it should be noted that these city-level scores derived from high-resolution data inevitably mask intra-urban inequalities.”
This means that in the same city, different communities might experience dramatically different levels of heat exposure and risk, depending on housing quality, income, access to electricity and green space. In many cities across Asia and Africa, extreme heat coincides with limited adaptive capacity.
Effective heat policy, the authors argue, must move beyond a single focus on reducing exposure and instead target all three dimensions of risk.
The study also highlights growing global reliance on air conditioning as a heat adaptation strategy, warning that it is not a universal or sustainable solution.
“Our study shows that heat risk planning needs to explicitly address not just exposure to high temperatures but vulnerability and coping capacity,” said Radhika Khosla, an associate professor at the University of Oxford.
“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.”
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”, said Khosla.
The study concludes that global heat risk is shaped by the interaction of climate stress with inequality and infrastructure, not temperature alone.
“This limitation is at odds with the IPCC’s [Intergovernmental Panel on Climate Change] conceptualisation of risk, which emphasises that risk emerges from the interaction between hazard exposure, vulnerability and response capacity.”
The researchers argue that only by integrating these dimensions can cities properly identify where the greatest risks lie and why they emerge.
“Addressing these gaps requires a harmonised framework that enables direct cross-city comparison while disentangling the relative contributions of different risk dimensions.”
Heat risk is about more than temperature. A new Oxford study of 205 cities found that poverty, limited infrastructure and lack of access to cooling are key factors driving urban heat vulnerability, with most of the highest-risk cities in South and Southeast Asia and Sub-Saharan Africa