Michael Richardson, Straits Times 15 Sep 08;
AS POLICYMAKERS plan ahead in Singapore and other major port cities, one of the most vexing questions they face is how much the sea level will rise.
The stakes are high. The number of people in 136 big port cities around the world is expected to grow threefold by the 2070s. If the prediction of scientists on global warming is correct, port cities will endure the intense effects of climate change, including sea-level rise, violent storms, flooding and land subsidence, according to a recent study for the Organisation for Economic Cooperation and Development (OECD).
The study, published in July, forecast that the value of flood-exposed economic assets in these cities could reach US$35 trillion (S$50 trillion) by the 2070s, approximately 9 per cent of projected global gross domestic product (GDP) then.
Bear in mind that the great port cities are often hubs of political and financial power - New York, London and Rotterdam; and in Asia, Osaka-Kobe, Shanghai and Mumbai.
The Intergovernmental Panel on Climate Change (IPCC) advising United Nations member states concluded late last year that the sea level would probably be somewhere between 18cm and 59cm higher by the end of this century than now, after a rise of 17cm in the 20th century.
The IPCC projection took account of water expanding in the oceans as it warmed. But it excluded additions to the ocean from water as the ice sheets that cover Greenland and the Antarctic melt. Yet these sources might produce the largest amounts of extra water flowing into the sea and adding to its volume. If the vast ice sheets melted completely, the sea level would rise by about 70m.
In a recent issue of Science magazine, a team of American glaciologists calculated how fast ice sheet glaciers would have to flow to raise sea levels by a given number of metres, and then considered whether these flow rates were plausible or even physically possible. The latter consideration is relevant because in Greenland and, to a lesser extent, in Antarctica, ice loss is limited by the number and width of rock-bound channels that form outlets for glaciers as they move, normally very slowly, from the land to the sea.
The team took account of the sea-level rise expected from ice melting in Greenland, Antarctica and the world's smaller glaciers and ice caps, as well as thermal expansion of the oceans. It concluded that the most likely scenario was a total sea-level rise of approximately 1m to 2m by 2100.
If these glaciologists are right, what will the impact be? The Tyndall Centre for Climate Change Research in Britain has warned that Asia - because of its vast coastline, many mega-deltas, big port cities and dense population - will be by far the most seriously affected region by a sea-level rise of this order of magnitude. It has calculated that a 1m increase in sea level would inundate more than 800,000 sq km of land in Asia, displacing more than 100 million people and causing a potential loss of nearly US$450 billion in GDP.
Of course, the impact would vary from country to country, depending on a nation's geography and ability to protect its urban centres, people and assets in low-lying coastal zones.
A couple of years ago, the World Bank commissioned a group of specialists to assess the consequences of sea-level rise in the range of 1m to 5m for 84 coastal developing countries. The specialists used high-resolution digital mapping to estimate the impact on each country's land, population, agriculture, cities and GDP.
Among the 84 countries surveyed were 12 in South-east Asia and North-east Asia that have low-lying coasts. The researchers concluded that within this century, hundreds of millions of people in the worst affected of the 84 countries are likely to be displaced, and that the associated economic and ecological damage will be severe for many.
In East Asia, Vietnam will be hardest hit. If the sea level were to rise by 5m, 16 per cent of Vietnam's land area would be inundated and 35 per cent of its more than 84 million people forced to move, resulting in a GDP loss of around 37 per cent. Even a rise of 1m in the sea level would displace nearly 11 per cent of Vietnamese and wipe out 10 per cent of their economy.
In relative terms, China was among the least affected of the 12 East Asian economies covered in the World Bank study, which was published last year. But in absolute terms, the damage would still be significant. It would be concentrated in low-lying areas along China's highly industrialised and urbanised eastern seaboard.
The OECD report found that 15 of the top 20 port cities ranked in terms of population exposed to coastal flooding from climate-linked storm surge and rises in sea level would be in Asia, with four of them in China.
The report said 13 of the top 20 port cities with assets exposed to coastal flooding in the 2070s would be in Asia, with six of them in China. The combined value of their flood-exposed assets is forecast to be almost US$9.2 trillion, with US$1.2 trillion of that amount in Hong Kong.
Singapore was not covered by the World Bank study. In the OECD report, it was given a relatively low risk rating for both population and assets exposed to coastal flooding in 2005 and in the 2070s. For example, Singapore's climate-exposed assets in the 2070s are projected to be worth around US$21 billion, putting it at No. 79 in the risk ranking for the world's 136 major port cities.
Two United States-based researchers concluded in 2005 that Singapore had the resources to protect its developed land zones from sea-level rise and inundation, and would be able to carry out effective adaptation measures.
The researchers found that the cost of protecting Singapore's developed coast - estimated at up to US$5.7 million per year by 2050, and as much as US$16.8 million per year by 2100 - was much less than the value of the land and assets at risk from coastal flooding.
One of the conclusions of the OECD report is that the likely impact of climate change and sea-level rise needs to be integrated into both coastal flood risk management and urban development strategies of vulnerable countries. Advance planning and investment are required because big projects, like the mechanical barriers near the mouth of the River Thames to protect greater London from tidal and storm surges, take 30 years or more from planning to completion.
The writer is an energy and security specialist at the Institute of Southeast Asian Studies.
