Battling Singapore’s Urban Heat Island Effect

Singapore city downtown in daytime by manjik from Getty Images Pro
The Urban Heat Island (UHI) effect, or trapped urban heat, explains why temperature differences of up to seven degrees Celsius exist between the urban and less built-up areas of Singapore.
According to the city-state’s Meteorological Service, Singapore has been warming up at twice the rate of the rest of the world. The effects of global warming, rising urban heat, and the El Niño phenomenon made 2023 the hottest year on record for the island nation.
Temperature increases can lead to adverse climatic effects, including a higher frequency of heat waves, droughts, extreme rainfall, and floods. A major contributor to rising temperatures is Singapore’s densely built urban landscape, where structures like buildings, roads, and vehicles trap and release heat into the environment, especially at night.


The Urban Heat Island (UHI) effect, or trapped urban heat, accounts for temperature differences of up to seven degrees Celsius between the city’s urban and less built-up areas. The consequences of rising temperatures can be severe for human beings, leading not only to thermal discomfort but also exacerbating health issues resulting from heat stress or excess heat trapped in the body. Heat stress occurs when the human body cannot adequately cool itself or dissipate the buildup of excess heat.

A Digital Solution to Urban Warming

“In an effort to mitigate urban heat, the Cooling Singapore 2.0 project was initiated in 2021,” said Graces Ching, a research assistant at the Singapore-ETH Centre, a collaboration between the city-state and ETH Zurich. “Climate research has been my focus since my undergraduate studies, and since graduation, I’ve been involved in researching the effects of trees and vegetation on ‘beating the heat’ in Singapore.”
Ms. Ching seized the opportunity to work on the Cooling Singapore 2.0 project for three reasons: her piqued curiosity in climate research, her interest in understanding the interactions between the atmosphere, humans, and the environment, and her desire to be part of a team developing one of Southeast Asia’s pioneering computational projects for reducing urban heat.
“The focus of Cooling Singapore 2.0 is to build a Digital Urban Climate Twin (DUCT) system, which models urban spaces using a system of models,” she elaborated. “Different scenarios can be simulated on the system. For example, different sizes, shapes or density of vegetation can be modeled so that we can develop an in-depth understanding of how the different scenarios affect the microclimate in the surrounding areas.”

The Digital Urban Climate Twin: A Powerful Visualization Tool

The Digital Urban Climate Twin (DUCT) is a digital representation and copy of a physical climate system. It incorporates all relevant computational models to account for environmental factors such as wind, sunlight, land surfaces, traffic, industrial and building energy models, as well as the movements of people. The DUCT factors in previous findings, data, and models of available UHI and outdoor thermal comfort (OTC) research, and can simulate past historical data to the current data being collected, ensuring the models produced are accurate, valid, and robust.
The DUCT can isolate the effects of urban heat, quantifying urban heat in selected areas to determine climatic outputs such as temperature, mean radiant temperature (the exchange of heat between a human and the surrounding environment), humidity, and wind speeds.
“Given that it is a powerful visualization tool, we wanted to design and develop the DUCT for urban planners and policymakers—people who are responsible for urban planning yet who might not have the expertise nor in-depth knowledge of urban heat, so that they can make sound and informed decisions for designing an environment that is more heat-resilient and thermally comfortable for the residents of Singapore,” Ms. Ching said.
“We want them to use the DUCT to invent, design, simulate and test different scenarios for reducing urban heat. If the scenarios test well and there’s high confidence that they will function well, then they can go ahead and build and turn the scenarios into reality.”

Project Advancements and Milestones

The project is progressing on schedule. Recently, a beta version of the DUCT was released for testing by urban planners and policymakers. In addition to gathering feedback from a select team of users from various Singapore government agencies, the researchers have embarked on the next phase of the project, which focuses on assessing the heat risks and impact of urban heat on human and biodiversity ecosystems.
One key insight emerging from the research is the complex role trees and parks play in combating Singapore’s urban heat island effect. While tree planting has long been touted as an antidote to rising temperatures, the findings suggest there is a saturation point beyond which additional greenery yields diminishing returns in terms of cooling.
Furthermore, the study underscores the importance of proper tree management. Overcrowded vegetation can impede wind flow, increase humidity levels, and trap air pollutants, ultimately undermining thermal comfort in the surrounding areas.
However, the presence of well-maintained parks can have a profound cooling effect, with temperatures up to 300 meters away from Housing Development Board estates registering noticeably lower readings. This phenomenon, known as the park cool island effect, is particularly pronounced during the day’s hottest hours, between 11 a.m. and 3 p.m., when the mean radiant temperature – the measurement of heat exchange between a human body and its environment – is reduced.
Beyond providing much-needed shade, trees and greenery also contribute to cooling through evapotranspiration, a process in which vegetation draws heat from the surroundings and dissipates it through evaporation. This natural mechanism further underscores the vital role urban greenery plays in mitigating the relentless rise of temperatures in Singapore’s densely populated cityscape.

Lead image courtesy of Manjik from Getty Images Pro

Materials Provided by Singapore Management University