The case for super cool materials to make Indian cities cope with the new climate normal of urban heat

Time of India

24-04-2025

Ansar Khan is an urban climatologist and an Assistant Professor at the Department of Geography at Lalbaba College, Calcutta University. He has several peer-reviewed publications in various academic journals. LESS ... MORE
Cities worldwide are experiencing a shift in their urban climate, with extreme heat becoming a defining challenge due to rapid urbanization and climate change. Indian cities, in particular, are facing unprecedented temperature surges, escalating public health crises, economic pressures, and infrastructure failures. Scientists warn that without urgent deployment of advanced heat mitigation strategies, urban centres will become increasingly unlivable, with dire consequences for human health, energy systems, and economic stability.
Rising urban temperatures have already led to record-breaking heat waves, with severe health impacts. Hospitals are reporting a surge in cases of heat exhaustion, dehydration, cardiovascular distress, and respiratory complications, disproportionately affecting vulnerable populations such as the elderly, children, and outdoor workers. Studies show that prolonged exposure to extreme heat heightens the risk of heat stroke, kidney failure, and mental health disorders, while also exacerbating chronic conditions like diabetes and hypertension. The urban heat island effect further intensifies the crisis by trapping heat, keeping night-time temperatures dangerously high, and reducing the body's ability to recover from prolonged exposure.
Beyond health concerns, extreme heat is placing immense pressure on energy infrastructure, with electricity demand for cooling skyrocketing. In cities like Kolkata, air conditioning use has surged by 40% during peak summer months, leading to frequent power failures. Many low-income households, unable to afford cooling solutions, remain at heightened risk of heat-induced illnesses and fatalities. Businesses, too, are suffering from increased cooling costs, reduced productivity, and economic losses as outdoor labourers face declining work hours due to unsafe working conditions.
While conventional cooling solutions such as tree plantations and green roofs are often considered, they face limitations in dense urban environments due to space constraints. Additionally, increased vegetation can sometimes raise humidity levels, promote volatile organic compound emissions, and contribute to ozone formation, worsening air quality. Recognizing these challenges, scientists are advocating for large-scale deployment of advanced heat mitigation technologies, particularly super cool materials, which have shown remarkable potential in reducing urban heat at scale.
Our research have demonstrated the effectiveness of these solutions in large-scale studies. The study in Riyadh, Saudi Arabia, assessed the impact of radiative coolers, reflective coatings, and hybrid green infrastructure across 3,323 urban buildings. The results were striking, with a peak temperature reduction of 4.5°C, a 26% decrease in annual cooling degree hours, and a 16% reduction in cooling energy consumption. When combined with energy-efficient adaptations, the total cooling demand fell by 35%, highlighting the potential of these technologies in mitigating urban overheating.
In Kolkata, where summer temperatures frequently exceed 40°C, super cool materials applied to roofs, walls, and pavements have been found to reduce peak air temperatures by 5.3°C, with sub-ambient cooling of up to 8.2°C during the hottest hours of the day. These materials utilize advanced radiative cooling and high-reflectivity coatings to dissipate heat into the atmosphere passively, significantly lowering temperatures without additional energy consumption. Unlike traditional cooling methods, super cool materials require minimal maintenance and can be scaled across dense urban landscapes, making them a viable solution for heat-prone cities.
Despite the severity of the crisis, public awareness remains low, and policymakers have yet to implement effective urban heat warning systems to protect vulnerable communities. Scientists emphasize that immediate government intervention is essential, with mandatory heat action plans, early warning alerts, and financial support for heat-resilient infrastructure.
Extreme urban heat is not a distant threat but a present emergency. Indian cities must act now to deploy large-scale cooling technologies and establish robust heat warning systems. Delaying action will lead to irreversible damage with severe consequences for human lives, economic stability, and environmental sustainability.
With climate change amplifying the urban heat island effect, the cost of inaction is rising rapidly. Scientists, urban planners, and health experts urge city authorities to prioritize climate-resilient urban design, energy-efficient cooling systems, and public education to protect millions from the growing dangers of extreme heat. Without immediate intervention, Indian cities, alongside other heat-prone regions worldwide, face the risk of becoming uninhabitable, threatening public health, economic viability, and overall quality of life.
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Views expressed above are the author's own.