Study calculates rise in sea level

COPENHAGEN, Denmark – 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. Temperatures at the two poles then were likely warmer than today by 5 to 9 degrees Fahrenheit, which is what scientists expect could happen again if the average global temperature warms 4 to 6 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 one another. 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 degrees 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, which is the temperature rise threshold that policymakers are hoping not to cross if they can seal a climate deal in Copenhagen.

Princeton University geosciences and international affairs professor Michael Oppenheimer, who co-authored the paper and is in Copenhagen observing the U.N.-sponsored talks, said the findings are “something to worry about.”

“Is this the end of the world? No,” he said. “Does it mean there’s a premium on reducing the level of greenhouse gases as fast as reasonably possible? Yes.”