How to Cool Down a City
Pablo Robles, Josh Holder and Jeremy White | The New York Times | September 18, 2023
https://www.nytimes.com/interactive/2023/09/18/world/asia/singapore-heat.html
Singapore’s prime minister has described climate change as “life and death.” He has reason to worry: Stifling temperatures and humidity already last all year, and the city-state has warmed at twice the global average over the past six decades.
Heat like this isn’t just uncomfortable. It can cause chronic illness and death, including heat exhaustion, kidney damage and even heart attacks. With two-thirds of the global population expected to live in urban areas by 2050, urban heat is an enormous global health challenge.
Rapid urbanization has made Singapore hotter. A big part of the problem is how almost every global city is built.
Cities cut down trees and remove plants that provide shade and naturally cool the air.
They cover large areas with concrete and asphalt, which absorb heat during the day and release it at night.
They densely pack skyscrapers into urban canyons that limit wind flow and trap pockets of heat.
And their residents expel waste heat from gas car exhausts and air conditioners, helping to transform a hot day into an unbearable one.
Preventing climate change is out of Singapore’s control: The city-state emits less than 0.1% of global carbon emissions. But there is a surefire way to limit city temperatures, researchers say: Revive the natural processes that cooled the land before urbanization.
Most cities do not have Singapore’s wealth and centralized political system, which allow it to move quickly to build new infrastructure. But while some of Singapore’s strategies to reduce excess heat are expensive, many of them are straightforward, and cheaper than planning for, say, floods or hurricanes.
As temperature records were shattered around the world this summer, Singapore’s blueprint for slowing the urban impacts of extreme heat is gaining urgency.
Researchers say that planting more trees is the most effective way to reduce a city’s temperature.
“If you wanted to invent the most effective kind of climate management technology from the ground up, you could spend a lot of time trying to do that. You would just engineer a tree,” said Brian Stone Jr., director of the Urban Climate Lab at the Georgia Institute of Technology.
The streets around the Khoo Teck Puat Hospital are lined with trees, and the central courtyard of the building is full of dense foliage. During the day, trees shield pedestrians from the beating sun and prevent the sun’s rays from warming the concrete sidewalk. At night, temperatures are lower, as there’s less heat released from the sidewalk.
In order to rely on trees to regulate climate stress, cities will need to treat them as infrastructure to ensure they are healthy and effective, according to Dr. Stone. That will come at a cost, but just a fraction of what cities spend on other environmental protections.
“It’s a real budget item, but it’s not out of proportion to what we already spend on environmental management in cities,” he said. “It’s less than 1 percent of what we spend maintaining storm sewers in L.A. every year.”
Singapore is also encouraging the integration of greenery directly into buildings by offering financial incentives for rooftop gardens and vertical green facades. The foliage works as natural blinds, shading the structure and insulating the building’s material from the heat, reducing the need for air conditioning.
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