During a devastating heatwave in May 2022, city surface temperatures reached a high of 60ºC, with the gap between temperatures in urban and rural areas as much as 25ºC. As India struggles to respond to heat waves and rising temperatures, the negative impacts of rapid urbanisation are worsened by urban heat islands (UHIs)—a climate change phenomenon where zones in a city trap heat and raise surface temperatures.
UHIs are caused by an abundance of highly-concentrated buildings, reduced vegetation, and dark pavements’ trapping and concentrating heat. As a result, these areas experience temperatures significantly warmer than surrounding rural areas. UHIs are exacerbated by other phenomena that already plague Indian cities, such as air pollution since high ozone concentration levels in cities prevent warm air from rising. Rapid urbanisation increases the intensity of UHIs as well. Poor urban planning leads to densely packed structures that trap heat.
Health Effects
UHIs pose a serious threat to public health. The most immediate health risk is a rise in heat-related diseases. Extreme heat can cause heat cramps, exhaustion, and heat stroke due to the inability of the body to regulate its temperature. The strain put on the body as it attempts to cool itself stresses the heart and kidneys and in turn can worsen existing health conditions, especially for vulnerable populations like young children, the elderly, and those with chronic illnesses. Furthermore, because of the correlation between UHIs and air pollution, studies have shown that UHIs are a significant risk factor for many respiratory diseases as well (Grigorieva and Lukyanets, 2021). The Global Center on Adaptation attributes over 10,000 deaths to heatwaves in India between 2010 and 2022.
Ways forward:
Cities should focus on decreasing the concentration of heat-retaining cement, asphalt, brick and stone and increasing the amount of green space. The initiatives of other cities around the world can give insights into how best to lower urban temperatures at the local level.
Increased Green Space
Singapore is a global leader in cooling high temperatures caused by urbanisation. The city has implemented initiatives involving building design and smart technology, but perhaps its most notable is its commitment to planting greenery. Singapore has successfully cooled down local areas by planting over 7 million trees and creating more than 300 parks and gardens, even integrating greenery into its buildings. For example, Khoo Teck Puat Hospital contains trees and plants in a central garden as well as on its rooftop.
Another city hailed for the success of its greenery initiatives is Medellín, Colombia. The government implemented more than 30 green corridors, connecting over 3.5 million plants in green spaces across the city. This initiative had a remarkable impact, reducing the city’s temperature by 2ºC. While greenery requires maintenance infrastructure, it is still a relatively cost effective option, costing less than 1 percent of what some cities spend on maintaining storm sewers and other environmental protections.
Cool Roofs and Pavements
Cool roofs and pavements are another strategy to mitigate the warming effects of infrastructure surfaces. Dark, or traditional, roofs and pavements aggravate UHIs because they absorb 80-95% of sunlight, warming local air. Cool roofs and pavements reflect sunlight and enhance water evaporation, reducing surface and internal building temperatures. New York City has championed this approach with its NYC CoolRoofs initiative which employs people from disadvantaged communities to install one million square feet of cool rooftops annually. Phoenix, Arizona, too, has experimented with implementing cool surfaces. The city’s 2021 cool pavement pilot program showed that cool pavements were roughly 5-6ºC cooler than dark pavements.
Smart Growth
However, cooling down a city can be as simple as planning the direction buildings are oriented. Smart growth is an approach to urban planning that considers energy conservation and the natural environment. For example, at Woodlands Health Campus in Singapore, buildings are orientated in a north-south direction and interspaced with greenery to curtail warmth trapping. Smart growth is an important tool for the future, a notable solution for rapidly urbanising cities.
Heat Alert Systems
Effective alert systems are also key to curbing the effects of UHIs. The India Meteorological Department provides heat alerts, but ensuring locals are aware of dangerous heat levels is up to the city. A successful example lies in Ahmedabad’s Heat Action Plan, the first of its kind in South Asia. The plan details departmental responsibilities and protocols for different heat alert levels and uses a colour-coding system to share information with vulnerable communities. If a similar infrastructure was implemented in all Indian cities, there would surely be a reduction in heat-related deaths.
Indian cities must act to curtail the effects of UHIs. Although UHIs are a severe public health crisis, there are several promising solutions that will hopefully reduce the negative health outcomes.
Ahalya Nambiar is an intern at Artha Global.
Banner image source: Canva
References
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“Heat Stress: The Silent Killer in Indian Cities.” 2023. Website Video. Global Center on Adaptation. https://gca.org/video/heat-stress-the-silent-killer-in-indian-cities/#:~:text=Between%202010%20and%202022%2C%2010%2C104,the%20urban%20heat%20island%20effect.
Laster, Laylonni. 2023. “Urban heat islands.” M-Group, October 10, 2023. https://www.m-group.us/m-lab/blog/2023/10/9/urban-heat-islands.
Mahajan, Shruti, and Laura Millan. 2023. “An Indian City’s Battle against Extreme Heat.” Bloomberg.com. June 19, 2023. https://www.bloomberg.com/features/2023-india-ahmedabad-extreme-heat/.
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Omolere, Mitota P. 2023. “Urban Heat Solutions: How Do Cities Adapt to Climate Change?” Earth.org. November 21, 2023. https://earth.org/how-cities-around-the-world-are-tackling-the-urban-heat-crisis/.
Rasmussen, Carol. 2022. “NASA’s ECOSTRESS Detects ‘Heat Islands’ in Extreme Indian Heat Wave.” Edited by et Propulsion Laboratory. NASA.. May 12, 2022. https://www.nasa.gov/missions/ecostress/nasas-ecostress-detects-heat-islands-in-extreme-indian-heat-wave/.
Robles, Pablo, Josh Holder, and Jeremy White. 2023. “How to Cool down a City.” The New York Times, September 18, 2023, sec. World. https://www.nytimes.com/interactive/2023/09/18/world/asia/singapore-heat.html.
“Street Transportation Cool Pavement Pilot Program.” n.d. www.phoenix.gov. City of Phoenix. https://www.phoenix.gov/streets/coolpavement.