Cities in South Asia are sizzling, with low-income residents bearing the brunt of urban heat stress. But researchers are finding ways to help them adapt

CLIMATE CHANGE MAY be upon us, yet if you say, “Heat wave,” a lot of people in developed Western countries still think, “Ah, summer.” Trouble sleeping? Crank up the A/C.

But it’s a different, distressing and increasingly dangerous story for tens of millions of low-income urban dwellers in major South Asian cities. Not only do many of these people work outdoors in intense heat by day, but they come home at night to small, cramped shanties with tin, concrete or stone slab roofs and no air conditioning. For months at a time, overnight temperatures in these homes never fall below 30 C, higher still during heat waves. And, barring any intervention, these conditions are expected to worsen — producing more frequent catastrophes like the heat wave that caused more than 2,400 heat-related deaths in India in 2015.

“You can’t properly sleep, you can’t be productive the next day and if it continues for a long time it leads to health risks,” says Christian Siderius, a climate adaptation and water resources management expert with Netherlands-based Wageningen Environmental Research.

Since 2014, Siderius has been a lead researcher on a multifaceted project funded by the International Development Research Centre and the United Kingdom’s Department for International Development that focuses on climate change impacts on water, resources and society in the Hindu Kush Himalayan region, including cities in the major downstream river basins. Specifically, he and a team of colleagues in Pakistan, India and Bangladesh have been studying urban heat stress at household, neighbourhood and city-wide scales with a goal of developing solutions to help vulnerable people adapt to and manage the risks.

At one level, there’s a lot known on this topic, Siderius says. Planting trees for shade and painting walls white offers some relief, for example. “But what we found is that the evidence in South Asia and the evidence base for poor households was very meagre,” he explains. “People knew that some things helped, but we wanted to be able say specifically what could help bring levels of heat stress in your home down by, for example, five degrees.”

Solutions, whether via the private sector, government or NGOs, also have to be extremely low-cost to be viable.

Getting those answers requires data. To obtain it, researchers outfitted cars with temperature and humidity sensors and every two weeks drove them through three cities — Delhi in India, Dhaka in Bangladesh and Faisalabad in Pakistan — recording conditions in different neighbourhoods. In each city, they also installed temperature loggers in the bedrooms of 200 non-air-conditioned homes in different low-income neighbourhoods that took readings every 10 minutes.

The results, plotted on heat maps, paint a complicated but revealing picture that stands in stark contrast to government weather records, which indicate a single temperature for the entirety of one urban area, such as Delhi. Data that researchers collected in that city in 2016, for example, showed that average household temperatures were four degrees higher — 30 C compared to 26 C — than the weather office figure.

Differences between neighbourhoods were equally stark. “We started our survey in shaded [more affluent] areas and then went to east Delhi, where there are the densest, poor neighbourhoods,” Siderius says. “During heat waves we saw that some shaded neighbourhoods were six degrees cooler. Of course, it might be difficult to green the whole of Delhi, but it’s an indication that keeping your green area, keeping your shading, could be very helpful in keeping the temperature down.”

Within homes, the biggest differences stem from building materials and ventilation. The worst homes, where researchers recorded average indoor nighttime temperatures as high as 36 C during protracted heat waves, had no evaporative coolers, poor ventilation and metal roofs. Add perpendicular ventilation, Siderius says, and you get, on average, a two-degree drop. “If you have opposite ventilation — an open door and window, say — it drops another two degrees. Add an evaporative cooler and you get under 30 degrees.”

In 2017, Siderius’s group began working with a local NGO, the Mahilia Housing Trust, to test the effectiveness of prefabricated modular roofs made with non-conductive materials that are cheap, waterproof and easily removed. If the results are positive, they will be factored into the project’s final recommendations to local and regional governments.

Kallur Murali, an IDRC project officer in Delhi, says other recommendations will emphasize providing more publicly accessible water stations and revising public-access policies to make it easier for people working outdoors to find shelter in public parks and other shaded locations.

Ultimately, Siderius says, “No single measure is enough to keep a city like Delhi livable. You have to think about neighbourhoods, you have to think about housing construction and you have to understand people’s knowledge of how to cope.”