Writer: Jennifer Eveland
Climate scientists calculate that by the end of the century, the temperature in Singapore will have risen by anywhere between 1.4 to 4.6°C1. Meanwhile here in tropical Singapore, where the hottest day on record was a scorching 37°C2 (degree Celsius), researchers are working on a project to understand how we experience heat locally and what we can do to cool our city.
What they’re studying is the Urban Heat Island effect, or UHI, the degree to which our urban built environment is hotter than neighbouring rural areas. In 2006, assistant professor Winston Chow and professor Matthias Roth from the National University of Singapore (NUS) reported3 that the UHI in Singapore can be as high as 7°C.
Visualising the urban heat island (UHI) effect using a numerical weather prediction model and an urban canopy model. Image credit: Cooling Singapore; visualisation by CIVAL at Singapore-ETH Centre
Since January 2017, researchers in the Cooling Singapore project have been mapping temperatures across Singapore - from forests to industrial parks, the Central Business District and housing estates - to better understand the extent of the UHI effect in Singapore. They have also identified knowledge and technology gaps, and have established a task force with government experts. The aim of this project is to develop a roadmap for developing the capabilities needed for Singapore to regulate its urban climate.
The project, funded by the National Research Foundation (NRF)’s CREATE programme, is led by the Singapore-ETH Centre - a collaboration between ETH Zurich and NRF - and brings together researchers from the Singapore-MIT Alliance for Research and Technology, TUMCREATE (established by the Technical University of Munich), and NUS.
Project leader Dr Heiko Aydt explains that there are 2 main causes for Singapore’s UHI. The first is incoming solar radiation, which heats up roads and buildings, with this stored heat being slowly released back into the environment. The second is the heat that is actively emitted by motor vehicles, power generation plants, industry and even household appliances, including ironically, air-conditioners.
UHI isn’t the only heat-related metric the project aims to quantify. It also seeks to assess how people experience this heat, which entails measuring their Outdoor Thermal Comfort (OTC).
Project coordinator Dr Conrad Philipp describes OTC as a condition of mind that expresses satisfaction with the thermal environment. “It is a complex condition to assess because it depends not only on environmental factors such as humidity, temperature and wind speed, but also on more subjective attributes such as a person’s outdoor exposure, current activity and past experience in different environments.”
While measured in different ways, the two metrics are obviously related – as UHI goes up, OTC goes down – though the exact correlation between them is difficult to establish.
To assess the UHI, the team uses a computer model that calculates the effect of urban morphology – including buildings and roads – upon air temperatures. The resulting map is validated against data collected from 14 weather stations operated by the Meteorological Service Singapore. The same model can be used to make a hypothetical map based on the assumption that Singapore is entirely covered by vegetation. The UHI is the difference in temperature between the 2 maps.
Assessing OTC has proved to be a bit trickier. To do this, the researchers choose a particular location where they monitor humidity, temperature and wind speed. They then ask passers-by a catalogue of questions related to their thermal comfort, including how hot or cold they feel, what activities they have been undertaking, and how long they have spent outdoors. The analysis of this data provided a better understanding of people’s comfort levels under different microclimatic conditions in the city.
The team has produced a number of outputs based on the data collected. One of these was an energy flow diagram, known as a Sankey diagram, which maps the sources and losses of energy in Singapore. This has proved useful for understanding which sectors contribute most to the UHI. It has shown that, outside of industrial energy use, the largest users of energy are transportation and buildings, with much of the energy consumed in buildings going into air-conditioning.
The team also conducted simulation studies to show how new developments or particular weather conditions might affect the UHI. For example, an analysis of the impact of UHI during an inter-monsoon season in April 2016 revealed that UHI effect can be as high as 5°C during the night. They are also studying how different interventions could affect meteorological conditions at the building and neighbourhood scale in Jurong Lake District, the Central Business District and a housing estate. Researchers are currently developing specific climate-responsive planning guidelines with quantitative and qualitative recommendations.
The study's task force in discussion. Photo credit: Cooling Singapore, Singapore-ETH Centre
The published works that have been launched by Cooling Singapore are accessible to everyone from students to policymakers, and include a catalogue of mitigation strategies which outlines 86 measures to reduce UHI and improve OTC and a guide to 24 simulation tools to assess the impact of different strategies in reducing UHI and improving OTC.
All of these outputs have the ultimate goal of facilitating climate-informed urban planning, by helping urban designers and architects make more informed decisions. Already the team has examined a number of urban design scenarios based on local factors such as block size, block orientation, aspect ratio (which is the building’s height in relation to the street’s width), building height profile and urban typology or form. “For example, in an ongoing study with URA, we investigate how we can improve thermal comfort by stimulating wind flow, through means such as increasing the heights of shaded pathways,” says Conrad. The URA modeling project is just one of many collaborative projects undertaken by the team based on their findings. Cooling Singapore has also played a role in the Orchard Road Business Study which included an analysis of shaded pathways, carried out under the Future Cities Laboratory at the Singapore-ETH Centre in collaboration with private sector partners.
Cooling Singapore has also undertaken 3 social campaigns to study the relationship between climate, urban space and people. “Our research wouldn’t be complete if we aren’t involving people in engagement studies, workshops and also surveys, in order to figure out how people feel about it and also about how open they are to certain mitigation measures,” says Heiko.
On-site measurements and surveys by the Cooling Singapore team to study the relationship between climate, urban space and people. Photo credit: Cooling Singapore, Linda Meisen Photography
More than 2,000 Singapore residents have participated in the social campaigns conducted in collaboration with the Singapore University of Technology and Design (SUTD) Lee Kuan Yew Centre for Innovative Cities and non-profit design group Participate in Design, which included face-to-face surveys, online surveys and workshops. Through workshops with residents, the group discovered that residents prefer strategies such as green streetscapes and void decks over cool bus stops or the introduction of renewable energy.
“In ensuring the robustness of our research, we are going into breadth in addition to depth, in the sense that we reach out to government agencies and citizens, through surveys and workshops,” says Heiko, who believes that the multidisciplinary feature of Cooling Singapore makes the study unique.
48 residents in Punggol ranked their preferences for strategies to improve outdoor thermal comfort during a workshop by the Cooling Singapore team. Image credit: Cooling Singapore and Dr Samuel Chng, Lee Kuan Yew Centre for Innovative Cities; graphic by Lea Reufenacht
As part of the project, a task force was created, which consisted of representatives from a range of government agencies such as the URA, Housing and Development Board, National Parks Board, Building and Construction Authority and the National Environment Agency and universities such as the SUTD and Nanyang Technological University.
“The Cooling Singapore project is different from a typical academic research project,” says Heiko. “The idea was to bring together all these different agency representatives who have expertise from their specific domains to keep us grounded in reality and provide important feedback for our studies.” In addition to establishing a two-way information loop, Heiko says that task force workshops have also facilitated inter-agency communication on the issues at hand.
For people who want to help reduce UHI in their everyday lives, Heiko suggests setting their air-conditioning temperature at least 4°C higher. If everyone in Singapore were to do this, the combined effect would be notable. Businesses, in addition to raising the air-conditioning temperatures, can also consider painting their buildings in lighter colours to reflect more of the sun’s rays.
At the city level, electricity generation could move offshore, away from the city, or even better, renewable energy could be encouraged. The increase in mixed-use districts is a promising trend. When residential, commercial, and recreational activities are located in close proximity, the need to commute to work is reduced. Access to goods and services and recreation is also more convenient, which could encourage walking and the use of public transport over the use of private vehicles.
Cooling Singapore is currently preparing a follow-up project that will take the urban planning and climate design concepts and link them to Virtual Singapore, a NRF project to create a dynamic three-dimensional city model and collaborative data platform.
“We’re also looking at a second phase, which would attempt to address issues that we identified in the first phase,” says Heiko, “to address the gaps but also widen the scope, because although the team is already multidisciplinary, with additional economic expertise, we will be able to answer questions such as, ‘What is the economic impact if we were to increase the temperature by a certain degree?’”
“We also want to have an educational component through courses because we feel that there would be a lot to be gained if we can share our knowledge with policy makers and others who can make a difference,” he says.
“We hope that the work that we do here can be shared with others. Singapore can be developed as a role model in this area, whereby we could export concepts and ideas that we develop here to other cities,” he adds.
For more information about the study, visit the Cooling Singapore website.
1. Source: National Climate Change Secretariat. https://www.nccs.gov.sg/climate-change-and-singapore/national-circumstances/impact-of-climate-change-on-singapore
2. Source: Meterological Service Singapore. http://www.weather.gov.sg/climate-historical-extremes-temperature
3. Chow, W.T.L., Roth, M., 2006. Temporal dynamics of the urban heat island of Singapore. Int. J. Climatol. 26, 2243–2260. https://doi.org/10.1002/joc.1364