Singapore is getting hotter and hotter. A recent non-government report highlighted that the city recorded 122 additional days of “dangerous” heat in 2024. Without climate change, the city could expect just four, according to World Weather Attribution (WWA) and Climate Central.
The Meteorological Service of Singapore (MSS) reports that Singapore’s average temperature has risen by 0.25°C per decade from 1948 to 2023, more than twice the pace of the increase in global temperatures across a similar period. While urbanisation and the concrete heat-island effect may well have contributed to some of that increase, the MSS notes that a certain amount of the gains could also be due to man-made global warming. Whatever the cause, the fact is that eight of the 10 hottest years on record for Singapore occurred since 2000; all of the top 10 were since 1997.
Surging temperatures are presenting new challenges for urban planners, said Dr Woo Jun Jie — Senior Lecturer at the Lee Kuan Yew School of Public Policy (LKYSPP), National University of Singapore — who studies global cities in Asia, with a strong focus on urban governance, policy design and economic development. Singapore may need to get creative in terms of how it designs for the heat, and one option that should be explored, among others, would be to look at moving some residential development underground.
“Underground spaces can help shield people from sudden shifts in temperatures as well as adverse weather events, since they are controlled environments,” said Dr Woo. “The technical capabilities for developing underground residential spaces may already exist, but it ultimately depends on public acceptance of these spaces.”
Singapore already has an Underground Masterplan in place. That document focuses on using the country’s subterranean assets for rail lines, utilities, warehousing and storage facilities so that the surface can be used for people-centric activities such as housing, parks and recreation. It is important to note that the current Underground Masterplan explicitly states that there are no plans currently to move housing beneath the surface.
“Any efforts to extend the Underground Masterplan will therefore necessarily involve extensive consultation,” said Dr Woo. “Underground residences would indeed provide Singapore with a useful option to deal with urban heat, although Singapore has also been exploring other options such as wind tunnels. In order to deal with extreme heat, Singapore will need to consider underground living as part of a broader suite of potential solutions.”
A benchmarking study conducted during the formulation of the Underground Masterplan noted that protecting residents from climactic conditions has been a reason for putting infrastructure underground in particularly cold climates, such as Finland’s Helsinki and Canada’s Montreal. However, even in those places, subterranean construction was limited to walkways, some consumer and recreational purposes and transport linkages. Residential construction was almost always kept above ground.
It is not unheard of for populations to move their living quarters underground where they see the need.
For instance, Derinkuyu in Turkey’s Cappadocia region is an underground city dating from as far back as 3000 years ago that could house as many as 20,000 people, complete with churches, schools and even wineries. There are several similar sites in the area. The general consensus is that the reason for Derinkuyu’s residents moving underground was defensive, and to escape persecution.
But modern instances of underground residential living are few and far between. Perhaps the best known is the opal-mining town of Coober Pedy in South Australia, where about 50% of the population live in subterranean homes to shelter from the intense heat and freezing night temperatures of the Australian desert.
Engineering and environmental challenges
“Coober Pedy could be a useful case study into how people have adapted to living underground,” the professor said, drawing a contrast between the arid, dry Australian desert and Singapore’s equatorial environment. “The challenges, particularly in terms of humidity and dampness, are also important factors to consider.”
Whereas Coober Pedy is located about 300 kilometres from the ocean and has barely 20 days of rainfall, Singapore is an island that receives exponentially more rain; The National Climate Change Secretariat (NCCS) notes that the amount of rainfall — already over two metres a year — is rising along with global temperatures and sea levels. Not only that, but Singapore’s underlying rock is much different to the prehistoric sandstone and siltstone into which the Australian town’s underground homes and facilities are carved.
“Much of our land consists of softer earth, which could pose challenges in building underground spaces. And the creation of more concrete infrastructure could also increase surface run-off, which could raise the risks of flooding.”
That said, advances in modern technology mean that the potential exists for establishing viable communities underground. The physical challenges are mainly to do with engineering and establishing the proper building and fire codes so that such spaces are safe. Even the lack of natural light can be overcome with technology from the Nordic states where solutions have been found to counteract their long, dark winters.
“There may be challenges in terms of waste management, with new systems that will need to be developed for the disposal of physical waste and discharge of wastewater,” noted Dr Woo. “The biggest challenge for residents would be the lack of natural ventilation and natural lighting. These are important factors for mental well-being. Urban planners will need to consider the use of artificial lighting that could mimic natural lighting as well as installing ventilation systems that can draw fresh air into underground spaces. Planners could also consider incorporating more greenery and green features into these spaces.
“Furthermore, Singapore's land constraints also mean that we will need to be very careful when making extensive excavations to develop underground spaces, as this could heighten the risks of sinkholes.”
Will the public accept such a move?
But even if we can build functioning homes under the surface that aren’t claustrophobic and can effectively simulate natural light, by far the biggest challenge would be getting the public to accept living underground.
“Overall perceptions of underground spaces have not been positive,” Dr Woo said. “There will therefore be a need to overcome the natural tendency for people to avoid living in underground spaces. Having said that, we have already developed extensive underground retail spaces, such as Ion Orchard, which people generally seem comfortable spending time in.”
Such challenges are not insurmountable, but the public will need to be brought along in an inclusive and educational process, if underground living is to become anything other than an interesting concept.
“Urban planners will need to engage in more public consultation in order to understand potential barriers and resistance to underground living,” Dr Woo said. “It will be helpful to design underground spaces that are more attractive and liveable, such as with more greenery and water features. Lastly, there will likely be the need for extensive public education campaigns in order to convince the public of the viability of underground living.”