SINGAPORE — The temperature had reached 86 degrees and was climbing. Humidity measured at 75 percent. The sun glittered off the tall buildings.
Fourteen volunteers, six climate researchers and a mobile biometeorological cart called “Smarty” geared up for a “heat walk” in the center of the Southeast Asian city-state. The volunteers had strapped on devices to measure their heart rate and the temperature of their skin. Winston Chow, the lead investigator, watched the scene as a bead of sweat formed on his forehead.
Mr. Chow and his team are part of Cooling Singapore, a multi-institutional project launched in 2017 with funding from the Government of Singapore. The current goal of the project is to build a computer model, or ‘digital urban climate twin’, of Singapore that will allow policymakers to analyze the effectiveness of various heat mitigation measures before spending money on solutions that may not work. It’s research the Singapore government hopes can be replicated around the world.
“People have always wondered what the critical component of the climate is that really affects your discomfort. Is it a low wind speed? Is it high air temperatures? Is it high radiation from the sun?” said Mr Chow, an associate professor of science, technology and society at Singapore Management University.
“We get to grips with that. It can help a lot with smarter urban design at the plan level, or with how individuals deal with heat,” he said.
Singapore’s wealth gives it the means to invest in such high-tech solutions. But researchers say the Southeast Asian state’s geographic location also makes it a good model for others, particularly countries in the tropics. Located near the equator, the island has year-round temperatures hovering around 88 degrees Fahrenheit. Like the rest of the tropics, it has the added burden of high humidity, averaging 84 percent.
The research is especially relevant when many countries are ravaged by record temperatures. Heat waves in Britain, China, Japan and much of Europe have caused deaths, turned lives upside down and forced tens of thousands of people to evacuate.
Scientists have warned that the combination of high heat and humidity — known as extreme wet-bulb temperatures — may be one of the deadliest effects of global warming. Prolonged exposure to certain thresholds of high heat and humidity makes it difficult for people’s bodies to cool down because they cannot perspire effectively. That can be deadly, even for healthy people. Young children and the elderly are especially at risk.
“We are very concerned about climate change,” said Zhang Weijie, director of energy and climate policy at the Ministry of Sustainability and Environment. “It’s an existential challenge for us.”
“It is so important for us to keep Singapore livable and to continue the activities we have now,” he added.
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Critics say Singapore could do much more to slow the potentially catastrophic effects of climate change. Nearly all of its energy supply comes from fossil fuels, and it is home to one of the world’s largest oil refining and petrochemical complexes. It encouraged the almost ubiquitous use of the air conditioner, which Lee Kuan Yew, Singapore’s first prime minister, once called the most important invention of the 20th century.
But constantly running air conditioners in the city-state became unaffordable. According to a 2019 government survey, about 25 percent of low-income households living in one- and two-bedroom social apartments have air conditioning. In 2019, a senior minister said air conditioners make up a “significant” share of carbon emissions from buildings and households, the second largest source after the industrial sector.
Gerhard Schmitt, lead researcher at Cooling Singapore, said the idea for the project came about because he asked a group of elderly residents in 2011 if Singapore had always been this hot. They told him that it had never been this bad before and that they had once been able to see morning dew on the grass.
Mr. Schmitt and his team of investigators began to investigate what had happened. It became clear that urbanization had made Singapore a lot warmer than before. In recent decades, the government has transformed the city-state by building tall skyscrapers, piling concrete, steel and glass where Singapore’s natural forests once stood.
That contributed directly to what climate researchers call the ‘urban heat island’ effect, where the difference between central Singapore and the forests in the northwestern part of the island can be more than 45 degrees.
In 2017, researchers from Cooling Singapore recommended 86 ways the city-state could change its planning, such as changing the direction of buildings to create wind flow and using district cooling systems — which direct chilled water to surrounding buildings to cool the air — in rather than depending on air conditioning.
They had also said that using reflective paint would be a good way to reduce the heat. But Peter Crank, a research fellow at Cooling Singapore, said they are expensive, so the “cost-benefit ratio is potentially challenging.”
Before Cooling Singapore, according to Mr Zhang of the Ministry of Environment, the government had not fully identified the biggest factors affecting heat. Now it can quantify how more greenery or reducing the number of cars in certain areas can affect temperatures — and adjust measures based on each district’s needs.
Previous heat studies have mostly relied on data from weather stations, which didn’t quite reflect what people like Rachel Pek, 23, felt on the ground.
With sweat pouring down her face, Ms. Pek, a climate researcher, drove the mobile cart around the Singapore Management University campus in central Singapore for about an hour. Some neighborhoods, especially those without shade, were much hotter than others.
On Bencoolen Street, where tall buildings block the morning sun, the average radiant temperature is – a metric that measures not only air temperature, but also the radiation of a person’s environment – was 82 degrees. About a third of a mile away, on Queen Street, which was exposed to more air, it was 127.4 degrees.
“The prevailing hypothesis now is that the presence or absence of shade in a place like Singapore is the critical determinant in adapting to heat exposure,” said Mr. chow. To address this, Singapore has pledged to plant one million trees by 2030 and has planted more than 388,000 trees to date.
But Mr Chow said it’s not just the number that matters, it’s the type of tree, ideally trees with “maximum shade canopies”. “If you have small trees, like palm trees, it won’t cut it,” he said.
One of the volunteers, Shamil Kuruppu, said he has stopped taking long walks, which he used to enjoy in his hometown in Negombo, Sri Lanka. Now he only trains in air-conditioned gyms.
“I really like it here,” said Mr. Kuruppu, 28. “The only complaint I have is the weather.”
Yuliya Dzyuban, a researcher at Cooling Singapore, said one of the goals the scientists now have is to find ways to create “islands of relief” in the city, places where people can get the feeling of a cool breeze or air conditioning after walking outside on a hot day.
Research has shown that small changes in urban design and vegetation can create these pleasurable sensations, Ms Dzyuban said. A better understanding of how and when people are exposed to heat could even help governments devise plans to encourage more people to take public transport, she added.
To get people to change their habits, “we need to think about how we can make their experiences more comfortable and enjoyable,” she said. “Because they wouldn’t do it otherwise.”