The Heat Is Online

Researchers See Sea Levels Rising Twice as Much as IPCC Projections

Sea Level Rise May Be Twice More Than Expected, Sept. 4, 2008


Goodbye Kiribati, the Maldives and much of the Netherlands. Farewell to low-lying cities. See you beneath the sea.


The poster children for global warming, these areas are living on the brink, utterly prone to drowning as the oceans rise. And if a new study is right, a lot more places will be added to the list sooner than anyone ever thought.


The United Nations Intergovernmental Panel on Climate Change (IPCC)'s worst projections for Greenland's contribution to sea level rise top out at 68 centimeters (27 inches) by the year 2100. Such a rise would imperil coastal cities around the world.


But Anders Carlson of the University of Wisconsin-Madison and a team of researchers say the problem is potentially a lot worse. They say the oceans could rise by as much as 1.3 meters (4.3 feet) by the end of the century, double the IPCC's estimate.


If the team's findings are right, some 145 million people living within 1 meter (3.3 feet)  of sea level would be in danger. By one United Nations calculation, a meter rise in the oceans would cost the world $944 billion in damages and lost productivity.


Governments in low-lying nations and cities should take heed, Carlson said. "They should be paying attention to the fact that the potential for sea level rise is greater than what they are planning for right now," he said.


To see how fast sea level may rise in the future, Carlson and his team looked to the ancient Laurentide ice sheet, which stretched as far south as Ohio and New York City during at the peak of the last Ice Age 20,000 years ago.


By 9,000 years ago, the ice sheet had retreated to Wisconsin and upstate New York near the Saint Lawrence River. Over the next 500 years it melted away even more, leaving behind boulders and new plant life. The team picked up these bread crumbs from the glacier's trail and analyzed them to figure out how quickly the ice melted, and how much the climate must have warmed.


"We got about 2 to 4 degrees Centigrade of warming in the summer," Carlson said. "Very similar to IPCC projections," for climate change by the end of the 21st century.


The team's study was published this week in the journal Nature Geoscience.


Mark Siddall of the University of Bristol in the United Kindgom said the study shows that ice sheets can respond much faster to warming climate than anyone ever guessed.


"You have all these old-school ice sheet modelers saying 'You can't have fast responses of ice sheets,'" Siddall said. "The take-home message here is: Oh yes you can, and in climate conditions that are at least similar to today's."