India’s Urban Heat Plans Are Growing — But So Is Concrete

From green shades to cold wards, municipalities are experimenting with measures to cope with rising heat. But the long-term solution lies in more climate-sensitive urban development.

Vaishnavi Chandrashekhar

Pic credit: Wikimedia Commons

Earlier this month, the municipal commissioner of Thane, a large city in the Mumbai metropolitan region, announced that green shades would be installed at six major traffic junctions to shield commuters, especially bikers and pedestrians, from the scorching sun. The measure, part of the city’s new ‘heat action plan’, sounds like a good step. But local environmentalists were quick to point out the irony: the city authorities were building artificial green canopies while destroying natural ones. According to news reports, at least 5000 trees in Thane have been cut down or damaged in recent years, largely due to civic projects.

 This contradiction cuts to the core of the challenge for cities in a warming world. Even as municipalities across India are adopting heat action plans, or HAPs, in response to climate change, much of their focus has been on short-term measures to protect people from the immediate impact of heatwaves and peak summer temperatures. But to actually cool cities down, heat resilience has to be baked into how they build and grow—from land use to infrastructure to green cover. As Thane shows, this isn’t happening yet, thanks in part to infrastructure pressures and developer interests. The consequences of this silo-ed policy making, or ‘adaptation gap’, could be severe for low-income and migrant communities who are most exposed to heat risk.

Cities face a double dose of heat. Global warming is making extreme temperatures and heatwaves more likely. But the very process of urbanisation also increases local temperatures, a phenomenon known as the urban heat island effect. That’s because concrete roads and buildings absorb heat, while the forests and trees that those buildings replace cool the air, both through evapotranspiration and by shielding surfaces from solar radiation. Studies have shown that urban areas can be between 2 degree Celsius to 10 degree Celsius hotter than the adjacent rural areas.

This ‘urban heat island effect’ shows up between city neighbourhoods too. A recent study in Mumbai found as much as a 13 degree Celsius difference between densely built-up neighbourhoods and greener ones. Informal settlements are especially vulnerable. Another study in Delhi found indoor temperatures in a slum regularly exceeding outdoor temperatures due to poor ventilation and construction materials. Low-income neighbourhoods also tend to have other infrastructural deficits, such as fewer trees and parks or water services, that make them more vulnerable to heat stress. These communities are less likely to be able to afford air conditioning, and are more likely to work outdoors as wage labourers or street vendors—which means they must cope with hot days as well as hot nights. In peak summer, their bodies don’t get a chance to cool down. In coastal cities, especially, humidity adds to the stress. 

Heat stress has an array of health impacts, from dehydration and heat strokes to aggravation of heart and kidney issues. Heat also threatens productivity and economic growth. A 2020 McKinsey report on heat in India found that as of 2017, heat-exposed work drives about 30 percent of GDP growth and employs about 75 percent of the labour force, some 380 million people. McKinsey projected that the number of daylight hours during which outdoor work is unsafe will increase approximately 15 percent by 2030. These “lost labour hours” due to increasing heat and humidity could put approximately 2.5–4.5 percent of GDP at risk by 2030, equivalent to roughly $150–250 billion, McKinsey said.

Hotter cities also mean turning up the cooling—which puts more pressure on power plants and pushes up planet-warming greenhouse emissions. About 24% of India’s households have an air conditioner or cooler, and that proportion is expected to grow nine-fold by 2050. As the United Nations Environment Program’s Cool Coalition says, “India’s cities cannot just air condition a way out of this extreme heat crisis."

The good news is that many cities are beginning to act. Heat action plans, however imperfect, are forcing civic agencies to think about the issue and prepare for future risk through expansions in health facilities, improved heat alerts, and emergency response plans. Such emergency preparedness is critical: Ahmedabad’s heat action plan is estimated to have saved more than a 1000 lives annually, largely due to locally customised heat alerts and greater preparedness at health facilities. 

However, many cities have been slow to implement larger-scale or longer-term structural interventions that would slow down urban warming. That’s a pity because experiments in India and around the world are throwing up some interesting solutions.

 Some of these innovations have to do with making cooling machines more efficient—from air conditioners that consume less energy to more experimental ‘district cooling’ systems. The latter entails supplying chilled water to a cluster of buildings through underground pipes; the water absorbs the heat in the buildings and then circulates back to the central plant where it will be rechilled and sent out again. This system uses much less power than conventional air conditioning, and is being tried out in some places, such as GIFT city in Gandhinagar. The catch? They can be expensive, and building underground pipes is easier in new developments than in already packed urban areas.

That’s why many cities are turning to “passive cooling”—cooling buildings and streets without machines, by using a combination of architecture, urban design, and greenery. Such passive cooling strategies, says UNEP, could cut cooling demand by 24% by 2050 and reduce emissions by 1.3 billion tons. One popular fix is “cool roofs,” where reflective coatings deflect sunlight. These have been shown to reduce indoor temperatures by up to several degrees Celsius, and have begun being adopted in cities such as Ahmedabad, Jodhpur, and Hyderabad. Meanwhile, Bhopal is working with the ‘Smart Surfaces Coalition’ to map urban surfaces and find ways to make the darkest surfaces more reflective, permeable, and green.

 Other Asian cities have gone even further. In Guangzhou, China, city planners created a large-scale cooling intervention around six natural ventilation corridors along the region’s mountains, water systems, and open spaces. Their plan includes widening some streets and decreasing the size of buildings to leverage these natural wind flows; using rooftop gardens and white roofs and walls to reflect sunlight; increasing water bodies and fountains in the city; as well as planting native trees. Planners are also restoring the use of climate-sensitive traditional materials and housing design in historic neighbourhoods.

Singapore, once the epitome of a concrete jungle, is promoting nature with a vengeance, from vertical greenery and roof gardens to urban farms and neighbourhood parks. And thousands of miles away, in the city of Medellín in Colombia, green corridors packed with trees are reported to have cooled down parts of the city by two degrees.

 India’s central government has launched an urban greening push—Nagar Van—offering funds for community-led city forests on plots of at least 25 acres. But in cities like Thane and Mumbai, such large areas may not be available for greening. And where they do exist, many are being cleared for development—as in Hyderabad, where the Supreme Court has halted the destruction of a 400-acre forest. And while large parks and urban forests help cool cities, small-scale greenery matters too—like street trees and local gardens. For outdoor workers and low-income residents without access to AC, these spaces can offer crucial relief. Yet policies don’t seem to acknowledge this: in Mumbai, public gardens close in the afternoon, right when people need them most.

As for Thane, the city’s heat action plan recommends longer-term measures including heat-resilient building design, tree plantation, and heat risk-informed urban planning. The last measure would mean that city officials must start weighing the hidden costs of cutting down trees—rising heat, poor air, and greater health risks—before approving the next flyover or road expansion or high-rise construction. They must think about greening not in terms of simple tree plantation drives—a hundred saplings here, a hundred there—but as a well-thought-out blueprint for ‘green and blue infrastructure’ across the city, with a focus on areas that need it the most. And this planning must start today, not ten years down the line after the concrete has set and the city has become even hotter.  

RISING HEAT

• Around 30% of the world’s population is currently exposed to life-threatening temperatures for at least 20 days a year, according to the United Nations

• Heat waves lead to 12,000 deaths annually across the world, says the UN

• One billion people face immediate risk from lack of access to cooling, the vast majority in Asia and Africa, says the UN

• A 1°C temperature increase correlates with an 18% rise in morbidity and a 35% increase in mortality, according to a review of articles on community-based heat adaptation intervention published in The Lancet 

• Mortality risk associated with heat was much higher among rural populations, particularly in low-income and middle-income countries, The Lancet review notes

Earth Shifts, a monthly column on The Migration Story, will analyse the impact of global green goals amid mounting climate uncertainties on lives and livelihoods. 

Vaishnavi Chandrashekhar is an environment and science journalist based in Mumbai.