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Washington PostBy Juliet Eilperin
Washington Post Staff Writer
Thursday, December 17, 2009
COPENHAGEN -- A new paper published online Wednesday in the journal Nature suggests that the world may face a long-term sea-level rise of 20 to 30 feet, even under a modest global temperature rise.
The study -- by Princeton and Harvard researchers -- focuses on a period known as the last interglacial stage, which occurred about 125,000 years ago. At that time, temperatures at the two poles were likely warmer than today by five to nine degrees Fahrenheit, which is what scientists expect could happen again if the average global temperature warms four to six degrees above pre-industrial levels.
The scientists collected 50 indicators of geological sea level from that time, including beach sediment and coral samples, and developed a statistical approach so they could compare them to each other. After factoring in how both the sea surface and the earth's surface responds to pressure from ice sheets, they determined a global temperature rise of 3.6 Fahrenheit would likely commit the planet to a long-term sea-level rise of at least 21.6 feet and possibly more.
The findings are significant because the estimate is higher than previous projections, which put the sea-level increase at between 13 and 20 feet at 3.6 degrees Fahrenheit, or two degrees Celsius, which is the temperature rise threshold that policymakers are hoping not to cross if they can seal a climate deal in Copenhagen.
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http://www.washingtonpost.com/wp-dyn/content/article/2009/12/16/AR2009121604191.html?hpid=topnews#
Everyone in your swim trunks!
Surf's up!
Good bye, Florida!
As part of the study, the researchers compiled an extensive database of geological sea level indicators for a period known as the last interglacial stage about 125,000 years ago. Polar temperatures during this stage were likely 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) warmer than today, as is expected to occur in the future if temperatures reach about 2 to 3 degrees Celsius (about 4 to 6 degrees Fahrenheit) above pre-industrial levels.
"The last interglacial stage provides a historical analog for futures with a fairly moderate amount of warming; the high sea levels during the stage suggest that significant chunks of major ice sheets could disappear over a period of centuries in such futures," Kopp said. "Yet if the global economy continues to depend heavily on fossil fuels, we're on track to have significantly more warming by the end of century than occurred during the last interglacial. I find this somewhat worrisome."
Oppenheimer added, "Despite the uncertainties inherent in such a study, these findings should send a strong message to the governments negotiating in Copenhagen that the time to avoid disastrous outcomes may run out sooner than expected."
The researchers determined through their analysis that there is a 95 percent probability that, during the last interglacial stage, global sea level peaked more than 6.6 meters (22 feet) above its present level. They further found that it is unlikely (with a 33 percent probability) that global sea level during this period exceeded 9.4 meters (31 feet).
Sea levels during the last interglacial stage are of interest to scientists and important to policymakers for several reasons. Most notably, the last interglacial stage is relatively recent by geological standards, making it feasible for climate scientists to develop a credible sea level record for the period, and is the most recent time period when average global temperatures and polar temperatures were somewhat higher than today. Because it was slightly warmer, the period can help scientists understand the stability of polar ice sheets and the future rate of sea level rise under low to moderate global warming scenarios.
Earth's Polar Ice Sheets Vulnerable to Even Moderate Global Warming; New Orleans, Much of Southern Florida, Expected to Be Permanently Submerged
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