Study Says 1 Billion Threatened by Sea Level Rise

Global warming may cause sea-level rises that can worsen the effects of storm surges and tsunamis.

A sudden swell in sea levels could be catastrophic for more than a billion people living in low-lying areas, according to researchers with the U.S. Geological Survey (USGS). In a study released on April 19, the team notes that rapid sea-level rises caused by warming can worsen the effects of storm surges and tsunamis in these areas, threatening the survival of nearly a quarter of the world’s population.

The study uses new mapping technologies to identify places around the world at greatest risk of losing land to rising seas, and to estimate the number of people who would be adversely affected. It is just one of several recent studies demonstrating that sea-level rise is accelerating much faster than projected. The 2007 assessment from the Intergovernmental Panel on Climate Change (IPCC), released earlier this month, reports that global sea levels rose at an average rate of 1.8 millimeters a year from 1961 to 2003, with the fastest growth occurring between 1993 and 2003 (an average rate of 3.1 millimeters a year). 

Scientists attribute the accelerated sea-level rise over the past decade to melting sea ice at the poles and to thermal expansion of the world’s oceans due to warming temperatures. According to the IPCC, satellite data since 1978 show that the annual average extent of sea ice in the Arctic has shrunk by 2.7 percent per decade, with losses of 7.4 percent per decade in the summer. The National Climatic Data Center and the World Meteorological Organization report that the annual summer ice loss now totals some 60,421 square kilometers, an area one-fifth the size of Germany.

At the current rate of warming, scientists forecast a sea-level rise 0.5 to 1.4 meters by the end of the century, far exceeding IPCC estimates of some 59 centimeters by 2100. The USGS researchers project that a rise of five meters could inundate 3.2 million square kilometers of coastal land, affecting close to 670 million people. They warn that if vast areas of land-based ice in Greenland and Antarctica are affected, the contribution to sea-level rise from melting ice and glaciers could magnify to global proportions.  

The USGS study was initiated following the 2004 Indian Ocean tsunami and 2005’s Hurricane Katrina, both of which pointed to the need for a tool to help low-lying countries estimate the damages from sea-level surges. The new mapping techniques allow researchers and policymakers to determine how much and what land could be lost at various sea levels, enabling them to develop more accurate damage estimates as well as contingency plans to better prepare for potential disasters.


This story was produced by Eye on Earth, a joint project of the Worldwatch Institute and the blue moon fund. View the complete archive of Eye on Earth stories, or contact Staff Writer Alana Herro at aherro [AT] worldwatch [DOT] org with your questions, comments, and story ideas.