Chapter 2. Signs of Stress: Climate & Water: Sea Level Rising
Sea level is a sensitive indicator of global warming since it is affected by both thermal expansion and the melting of land-based glaciers. The respective contributions to sea level rise of thermal expansion and ice melting are estimated to be roughly the same.23
During the twentieth century, sea level rose by 10–20 centimeters (4–8 inches), more than half as much as it had risen during the preceding 2,000 years. If the earth’s temperature continues to rise, further acceleration is in prospect. The model used in the Intergovernmental Panel on Climate Change 2001 Assessment projects that sea level could rise by as much as 1 meter during the twenty-first century.24
Rising sea level has numerous consequences. The most obvious is inundation as the oceans expand at the expense of continents. Another is saltwater intrusion. As sea level rises, salt water may invade coastal freshwater aquifers. This intrusion is exacerbated by the falling water tables that now plague coastal regions in many countries, including Israel, Pakistan, India, and China. A third effect is beach erosion: as waves break further inland, they erode the beach, compounding the effect of rising sea level.25
The most easily measured effect of rising sea level is the inundation of coastal areas. Donald F. Boesch, with the University of Maryland’s Center for Environmental Sciences, estimates that for each millimeter rise in sea level, the shoreline retreats an average of 1.5 meters. Thus if sea level rises by 1 meter, the coastline will retreat by 1,500 meters, or nearly a mile.26
With a 1-meter rise in sea level, more than a third of Shanghai would be under water. For China as a whole, 70 million people would be vulnerable to a 100-year storm surge. The rice-growing river floodplains and deltas of Asia would be particularly vulnerable. A World Bank analysis shows that Bangladesh would be hardest hit, losing half of its rice production—the food staple of its 140 million people. (See Figure 2–4.) At current rice prices, this would cost Bangladesh $3.2 billion. Residents of the densely populated river valleys of Asia would be forced into already crowded interiors. Rising sea level could create millions of climate refugees in Bangladesh, China, India, Indonesia, the Philippines, and Viet Nam.27
Two thirds of the Marshall Islands and Kiribati would be under water. The United States would lose 36,000 square kilometers (14,000 square miles) of land, with the middle Atlantic and Mississippi Gulf states losing the most. And large portions of lower Manhattan and the Capitol Mall in Washington, D.C., would be flooded during a 50-year storm surge. A 1-meter rise in Japan would mean that 2,340 square kilometers of the country would be below high tide. Four million Japanese would be affected, many of them driven from their homes.28
Coastal real estate prices are likely to be one of the first economic indicators to reflect the rise in sea level. People with heavy investments in beachfront properties will suffer most. A half-meter rise in sea level in the United States could bring losses ranging from $20 billion to $150 billion. Beachfront properties, much like nuclear power plants, are becoming uninsurable—as many homeowners in Florida, for example, have discovered.29
Many developing countries already coping with population growth and intense competition for living space and cropland are now facing the prospect of rising sea level and substantial land losses. Some of those most directly affected have contributed the least to the buildup in atmospheric CO2 that is causing this problem.
Rising sea level will pose difficult and costly choices. Consider, for example, the effort and cost involved in relocating a million Chinese from the area to be inundated by the Three Gorges Dam. This would be trivial compared with the tens of millions, and eventually hundreds of millions in Asia, who would have to be relocated as the ocean rises if we continue with business as usual. Climate refugees may come to dominate the international flow of migrants since they are losing not just land, but food supplies and livelihoods.30
More than 90 percent of the world’s ice is in the Antarctic ice sheet, which, partly because of its size, is comparatively stable. The other 10 percent, however, is in the Greenland ice sheet and mountain glaciers, which are more vulnerable to climate change. Now that the Greenland ice sheet has started to melt, we must ask, What if this trend continues? Greenland’s ice sheet is up to 2 kilometers (1.2 miles) thick in some areas. In an article in Science, NASA scientists calculate that if the Greenland ice sheet were to disappear entirely, sea level would rise by a staggering 7 meters (23 feet), markedly shrinking the earth’s land area and engulfing many coastal cities.31
For the first time since civilization began, sea level has begun to rise at a measurable rate. It has become an indicator to watch, a trend that could force a human migration of almost unimaginable dimensions, and one that will shape the human prospect. It also raises questions of intergenerational responsibility that humanity has never before faced.
23. Stuart R. Gaffin, High Water Blues: Impacts of Sea Level Rise on Selected Coasts and Islands (Washington, DC: Environmental Defense Fund, 1997), p. 6.
24. Ibid.; IPCC, "Summary for Policy Makers: A Report of Working Group I of the Intergovernmental Panel on Climate Change" (February 2001), viewed at www.ipcc.ch/pub/spm22-01.pdf, pp. 2, 10.
25. Saltwater intrusion information from James E. Neumann et al., "Increases in Global Temperature Could Accelerate Historical Rate of Sea-Level Rise" (Washington, DC: Pew Center on Global Climate Change, 29 February 2000).
26. Boesch cited in Bette Hileman, "Consequences of Climate Change," Chemical & Engineering News, 27 March 2000, pp. 18-19.
27. Figure 2-4 from World Bank, World Development Report 1999/2000 (New York: Oxford University Press, 2000), p. 100; $3.2 billion figure estimated from USDA, op. cit. note 12, and from U.N. Food and Agriculture Organization, Rice Market Monitor, March 2001, p. 13.
28. James E. Neumann et al., Sea-level Rise & Global Climate Change: A Review of Impacts to U.S. Coasts (Arlington, VA: Pew Center on Global Climate Change, 2000), p. 30; Japan from Center for Global Environmental Research, Data Book on Sea-Level Rise (Tokyo: Environment Agency of Japan, 1996), pp. 67-68.
29. Neumann et al., op. cit. note 28, p. 31.
30. "China Says Huge Dam Project is Going Smoothly," New York Times, 26 October 2000.
31. Mastny, op. cit. note 14; Dorthe Dahl-Jensen, "The Greenland Ice Sheet Reacts," Science, 21 July 2000, p. 404-05.
Copyright © 2001 Earth Policy Institute