Robust Sea-Level Projections for Singapore by 2100 and 2150

Rising sea levels pose a critical challenge for low-lying countries such as Singapore, highlighting the need for accurate projections to inform adaptation strategies. However, data limitations, climate model uncertainties, and regional deviations complicate these projections. Here, we evaluate relative sea-level rise (RSLR) projections for Singapore by 2100 and 2150 based on Singapore's Second National Climate Change Study (V2), UK Climate Projections 2018 (UKCP18), the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6), and new V3 projections. Projections are provided under low (RCP2.6/SSP1-2.6) and high (RCP8.5/SSP5-8.5) emissions scenarios at six tide gauges across Singapore. The V3 projections reflect a correction to the erroneous tide-gauge record at Sembawang, which affected the contribution of vertical land movement (VLM) to the IPCC AR6 projections. The correction shows VLM adds 0.14 m by 2100 and 0.21 m by 2150 to RSLR at Sembawang. By 2100, V3 projections indicate a RSLR of 0.42 m (likely range: 0.26–0.63 m) under low emissions increasing to 0.67 m (0.38–1.07 m) by 2150. Under high emissions, RSLR is 0.75 m (0.58–1.04 m) by 2100, increasing to 1.32 m (0.9–1.95 m) by 2150. We find that ocean sterodynamics is the largest contributor to RSLR (∼40%) although uncertainties related to Antarctic ice sheet contributions are greater. Our findings highlight the need for accurate data especially from historical archives to improve the robustness of VLM and RSLR projections in Singapore and elsewhere.