SEA LEVEL RISE
Sea level rise can be defined as an increase in sea level caused by global warming through two main processes: the thermal expansion of sea water and the rapid melting of land ice.
The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC 2007) projects an increase of temperature ranging between 1.1 and 6.40 C over the next century, necessarily entailing a reduction of the amount of ice. As a result, sea levels could rise 10 to 23 inches by 2100.
A third of the world’s population living within 50 km of the coasts and a large percentage of them live much closer to the shoreline. Even a modest sea level rise could inundate low-lying regions, accelerate coastal erosion and force the relocation of communities and infrastructures.
Although it is not well established how fast the ice sheet will melt, if the Greenland and the West and East Antarctica ice sheets were to melt, it would be enough to raise the sea level by approximately 65 meters. The EPA approximates that 10,000 square miles of land would be erased by a two-foot rise in sea level. A one-foot rise in sea level might well translate to a 200-foot retreat of shoreline. In addition, the IPCC suggests that by 2080, sea level rise could convert as much as 33 percent of the world’s coastal wetlands to open water (IPCC 2007).
Sea level rise is also expected to make coastal cities more vulnerable to extreme weather (such as hurricanes) as well as to destroy important ecosystems such as wetlands and mangroves. Rising sea level inundates low-lying lands, erodes shorelines, exacerbates flooding, and increases the salinity of estuaries and aquifers. Islands are particularly exposed as many are gradually facing the loss of their fresh water supply due to salt-water intrusion. Low-lying coastal areas and deltas (the land where rivers feed into the ocean) house at least 300 million people and are particularly threatened by sea level rise.
Some developing countries are especially exposed to sea level rise due to their low- lying nature and limited financial resources to respond. Among the most vulnerable are countries with large populations in deltaic coastal regions such as Bangladesh, Vietnam, China and Egypt.
Two populous island nations, the Philippines and Indonesia, have millions who face displacement from their homes from sea level rise. Several small island state nations including the Maldives in the Indian Ocean and the Marshall Islands and Tuvalu in the Pacific could face extinction within this century if rates of sea level rise accelerate.
Figure 1: Causes of sea level rise from climate change. (2002). In UNEP/GRID-Arendal Maps and Graphics Library. Retrieved 17:10, March 26, 2008 from http://maps.grida.no/go/graphic/causes-of-sea-level-rise-from-climate-change.
Additional Resources
Nicholls, R.J., P.P. Wong, V.R. Burkett, J.O. Codignotto, J.E. Hay, R.F. McLean, S. Ragoonaden and C.D. Woodroffe, 2007: Coastal systems and low-lying areas. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 315-356. http://www.ipcc-wg2.org/index.html
EPA. “Coastal Zones and Sea Level Rise.” Updated 08 February 2008
Union of Concerned Scientists. "Highlights from the First Section of the IPCC Fourth Assessment Report."
Articles on Rising Sea Level
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