In a study conducted by the University of Oxford, Mumbai, Nagpur and Pune have emerged among the top 50 cities vulnerable to heat risk.

Heat risk vulnerability measures a population’s susceptibility to the harmful physical, social and economic impacts of extreme heat.

As part of the study — titled Moving beyond exposure: a globally comparable framework for heat risk assessment in cities — living conditions of people across 205 cities around the world with a population of more than 1 million were analysed.

Key indicators on which the study was based include hazard exposure, coping capacity and vulnerability. The study comes at a time when several nations including India are reeling under El-Niño – a climatic phase which occurs when trade winds weaken, pushing warm water towards the global east. As a result, El Niño leads to rise in temperatures globally .

Since March, several cities in India including Mumbai, Nagpur and Pune have been reeling under a heatwave and orange alert owing to El Niño conditions.

According to the report, 14 Indian cities emerged in the top 50 that are vulnerable to heat risk. This was followed by Nigeria and Pakistan, which have 5 and 4 cities each included in the list. The study shows that Maharashtra’s Nagpur, Pune and Mumbai were in the fourth, 23rd and 46th positions on the list. Other Indian cities that made it to the list include Ahmedabad at the second position, Madurai at the seventh, Bhopal at 15 and Kanpur at 20. The report showed that Nagpur was the second most vulnerable city in India after Ahmedabad.

“Heat risk in cities is not solely determined by temperature extremes but by the combined effects of environmental conditions, including humidity, mean radiant temperature, wind speed, socio-demographic vulnerability and system-level capacity to cope. As a comparative diagnostic tool, the results suggest that global heat risk planning can benefit from moving beyond hazard-centric approaches toward component-targeted strategies that explicitly address hazard exposure, vulnerability, and coping capacity,” the report stated.

“Conversely, several cities, including face severe risk under moderate exposure due to the socio-economic vulnerability and infrastructural deficits. While air conditioning can reduce acute heat stress for those with access, reliance on it as a primary adaptation pathway is not sustainable, particularly given its high cost and energy-intensive requirements. Increased fossil fuel-based electricity demand, high global warming refrigerant gases, and waste heat emissions can exacerbate urban warming over time,” the report stated.

The study was carried out by developing a risk index, which was classified into three categories – hazard exposure, vulnerability and coping exposure. The risk index was further assessed by considering socio-economic factors which include the demographic and socioeconomic conditions that increase susceptibility to heat-related illness and mortality, such as age and financial means and access to cooling infrastructure such as air conditioning, and ecological buffers such as tree cover.

For example, the population in Mumbai was compared with access to cooling structures and vulnerability scores were assessed.

“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,” said lead author Nethmi Jayaratne Kariyawasam, a DPhil lead author of the study and researcher at the Oxford Smith School of Enterprise and the Environment.

Radhika Khosla, associate professor at the University of Oxford, who co-supervised the research said the study indicates that there is a heat risk planning that needs to be explicitly addressed and not only the exposure to heat risk.

“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.