SINGAPORE - Researchers from Singapore will be working to update sea level rise projections for Singapore and the region by taking into account what is known as “black swan” events.
These refer to events that are less likely to occur - such as irreversible ice sheet collapse - but can impact low-lying countries like Singapore greatly if they do.
This move to update the Republic’s projections for sea-level rise – which is estimated to go up by up to 1.15m by 2100 – comes after an NTU study showed that global sea-level rise could be higher than earlier projections, if extreme events were considered.
The NTU study, published in December 2024, had focused on global projections, and found that mean sea-level around the world could go up by up to 90cm higher than earlier estimates.
Now, the Centre for Climate Research Singapore, which is under the Meteorological Service Singapore (MSS), said it will be working with NTU to localise the projections for Singapore and the region.
CCRS research scientist Trina Ng, who helped to put together the Republic’s projections revealed in early 2024, added that the collaboration with NTU will provide an additional set of projections that can be useful for various adaptation planning measures.
“Mean sea level is not uniform across the world. Different parts will vary differently from the global average because of processes such as ocean circulation and local vertical land movement. So if we want the most accurate and robust projections for Singapore, you have to localise it,” she said.
There are two ice sheets on the planet – one in Antarctica, the other in Greenland. If both were to melt completely, they could raise sea-levels by 65m.
One possible extreme sea-level event is the collapse of the West Antarctic ice sheet – its glaciers and ice shelves sit precariously over the warming ocean, which licks away at the underbelly of the frozen mounds, making the region more unstable.
This could lead to a rapid collapse of large parts of the ice sheet, dumping a large amount of ice into the ocean, triggering a domino effect and raising global sea levels by several meters over centuries. Even though this collapse happens gradually, it is irreversible.
But these processes are not well understood nor well captured in the climate models used to project sea-level rise, said MSS.
“Some of these large uncertainties come from the fact that we don’t have long enough observations. Everything to do with the ocean and ice involves a long, slow process... These changes could be irreversible, which means that they’re not going to come back and re-form over the next few hundred years once these big ice sheets break off,” said Dr Aurel Moise, deputy director of the climate research department at CCRS.
The UN climate science body previously projected that global sea levels could go up by between 0.63m and 1.01m by 2100 – with a 66 per cent probability – if no action to reduce greenhouse gas emissions was taken. Such probabilities are assigned using statistical analyses.
Singapore’s projections for sea-level rise had incorporated these forecasts by the Intergovernmental Panel on Climate Change (IPCC). The movement of land – whether it sinks or rises over time – also plays a critical role in shaping local sea level changes, and so data on these were also taken into account.
Due to the uncertainties associated with these so-called low-likelihood, high-impact ice sheet events, the IPCC had acknowledged those scenarios without assigning any probabilities of these events actually happening. They were tagged as low confidence projections.
Recently, NTU researchers used a different forecasting method, by merging data from various sea-level projection models with expert knowledge and insights about the lesser known ice sheet processes. They called this the fusion method, which was done in collaboration with scientists from the Netherlands’ Delft University of Technology.
Their study showed that under a high-emissions scenario, the projected global sea-level rise is between 0.5m and 1.9m instead by 2100 – with the high-end projection up to 90cm higher than the IPCC’s.
This research, led by NTU’s Dr Benjamin Grandey, was a project supported by the National Sea Level Programme under CCRS.
CCRS will be working with NTU to use the fusion method to generate high-end sea-level projections for Singapore and the region.
Dr Grandey, a senior research fellow at the NTU School of Physical and Mathematical Sciences, said: “Our new contribution will be... a worst-case high-end projection that quantify unlikely possibilities.”
He added that these worst-case scenarios are important to consider when planning for and protecting long-lasting critical infrastructure such as Singapore’s airport and ports. Such infrastructure on coastal land will include Changi Airport Terminal 5 and Tuas Port.
And what happens in the Arctic and Antarctic does not stay there. In fact, their ice loss could spell bigger troubles for the tropics than the rest of the world. This is because when the ice sheets at the poles melt, the increased ocean mass migrates to the tropical region due to stronger gravity near the equator, explained CCRS’ Ms Ng.
In finding out how “black swan” events could affect Singapore and the region, Dr Grandey and his team’s fusion method will be applied to the existing sea level rise projections in Singapore, as well as to the IPCC’s regional projections.
At Budget 2025, it was announced that Singapore’s Coastal and Flood Protection Fund – to safeguard the country from rising seas and floods – will receive a $5 billion boost.
Ms Hazel Khoo, director of national water and coastal protection agency PUB’s coastal protection department, said sea level rise is a progressive and dynamic process, and continuous adaptation is required.
When asked about the joint study between NTU and CCRS, she said: “Predictions of sea level rise will continue to evolve and be refined as climate science progresses and more data becomes available.”
To that end, PUB’s coastal protection measures and planning are expected to cover a 2m mean sea level rise scenario.
“This builds in flexibility for subsequent adjustments, should there be any new developments in climate science,” said Ms Khoo.
Shabana Begum is a correspondent, with a focus on environment and science, at The Straits Times.
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