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SEA LEVEL RISE PROJECTION AND ADAPTATIONS FOR MALAYSIA

This report provides updated future projections of sea level rise (SLR) along Malaysian coastlines, which are based on the updated processes generated by the global climate models or Earth system models from the 6th Phase of CMIP (i.e CMIP6) and also new methodologies recognised by the Intergovernmental Panel on Climate Change (IPCC) 6th Assessment Report (AR6) era. Sea level has fluctuated across the South China Sea (SCS), with rates ranging from 3 to 5 centimeters every decade. In general, open ocean areas have lower sea level trends of roughly 2-3 cm/decade, whereas near-coast locations show greater trends of 3-5 cm/decade. Specifically, the eastern and northern coasts of Sabah have seen faster rates of sea level rise than the Strait of Malacca. The sea level along Malaysia's beaches has risen in recent decades. This is based on evidenced from both the tide gauge records as well as satellite altimetry. A robust linear regression analysis was conducted to compare the rate of change between local tide gauges and satellite altimetry data from 1993 to 2018. The estimated sea level trends from tide gauge average at 3.8 mm/year (excluding Miri and Sejingkat), while satellite altimetry yields an average of 4.4 mm/year. The SLR trends are generally higher in satellite altimetry except for Pulau Langkawi, Johor Bahru, and Kukup. The coastal areas of Sabah and the north-eastern coast of Peninsular Malaysia exhibit faster sea level rise compared to other regions. Both tide gauges and satellite altimetry indicate slightly larger sea level rise over the Malaysian coast compared to the global mean sea level rise since 1993. Kukup records the highest sea level change rate (5.9 mm/year) among tide gauge stations, while Bintulu in Sarawak shows the lowest trend (2.4 mm/year). Lahad Datu has the highest changing rate (5.6 mm/year) based on satellite altimetry, and Pulau Langkawi exhibits the lowest rate. The satellite altimetry data generally show slightly higher surface height anomalies compared to tide gauge records. The differences between satellite altimetry and tide gauge measurements may be attributed to localized coastal processes. Tool has been developed to extract the projection of SLR around SCS and adjacent regions. The future projections of sea levels based on the latest IPCC AR6 scenarios (ie. Shared Socioeconomic Pathways, SSPs) for the selected tide gauge locations, up to time horizon of 2100 are reported. The projections reflect the medium confidence processes as in IPCC AR6 and consider the contributions from thermal expansion, Greenland and Antarctic ice-sheets dynamic, glacier melting, changes in land water storage and also take into account regional changes from regional ocean dynamic based on the CMIP6 climate models, glacier isostatics adjustment and gravitational, rotational and deformation effect. Table S1 shows the projected changes of future sea levels at Malaysian coastline. The future changes in sea levels along the Malaysian coastlines vary across different SSPs by the end of the 21st century. The projected sea level rise ranges from approximately 0.4 m for SSP1-1.9 to around 0.9 m for SSP5-8.5, toward the end of 21st century. Despite marginal spatial variations, the SLR is slightly faster along the Sabah coastline but lower along the west coast of Peninsular Malaysia. Similar spatial variations in projected changes are observed for lower emission scenarios. Although the specific stations with maximum or minimum changes may differ, the sea level along the Sabah coastline is projected to rise more compared to other coastal areas. The projected median changes of sea level provided in this report is generally higher compared to the one reported in Impact of Climate Change: Sea Level Rise Projection for Malaysia 2017, NAHRIM (2019) by about 10 to 14 cm. In addition, the upper bounds of current projections are remarkably higher compared to the previously estimated in NAHRIM (2019). Local adaptation strategies need to consider these changes in the projection uncertainties. SLR is inevitable and is already starting to have an impact along the coastline of Malaysia. Coastal flooding, bund breaches and coastal erosion that occur along the coast could be attributed to SLR. Thus, this report has provided strategies and adaptation references for four (4) types of land use: Agriculture, Port & Harbour, Recreational & Tourism and Urban Areas. Planners, developers, managers and individual investors involved in land use development are recommended to consider this strategy coupled with the magnitude of SLR from this report (Figure 3.8 to Figure 3.28) in order to minimize the adverse effects of SLR on their project components.