2 studies say polar ice melting fast

Polar ice sheets are melting faster than authorities realize and could submerge coastal communities worldwide, according to two studies released today.

Researchers from the University of Arizona and the National Center for Atmospheric Researchers (NCAR) noted that sea levels rose 20 feet during a warming period 129,000 years ago and said the waters could rise just as high after 2100 if global temperatures continue to climb.

Scientists have been warning for decades that carbon dioxide and other so-called greenhouse gases from power plants and car exhaust are warming the planet and raising the seas. They say the best way to minimize the damage is to drastically reduce smokestack and tailpipe emissions.

While some researchers dispute specific aspects of global warming, more than 2,000 scientists from 100 countries who served on the Intergovernmental Panel on Climate Change concluded in 1995 and 2001 that global warming is real and that carbon dioxide produced by humans is largely to blame.

The two studies published today in the journal Science say the impact of melting from Antarctica's ice sheets has been underestimated.

That melting will exacerbate effects of global warming and play a major role in submerging many coastal communities if nothing is done to curb the emissions, the researchers say.

No one is sure of the extent of the melting or the timing of its effects. But the researchers say that with the warming climate, melting ice sheets in Greenland, the Arctic and Antarctica could inundate coastal areas around the world.

Maps released with the studies show extensive coastal areas in Florida, New Orleans and Cape Cod, Mass., the researchers say might one day be submerged.

"As [Hurricane] Katrina pointed out, we only need a meter [about 3.2 feet] of sea-level rise to make much of New Orleans unlivable. The same goes for a number of coastal areas," said Jonathan Overpeck, a geosciences professor at the University of Arizona and lead author of one study.

For many scientists, this is hardly news: Two years ago the Maryland Department of Natural Resources and the U.S. Geological Survey began releasing maps, based on aerial photography and computer models, showing low-lying areas on the state's Eastern Shore most susceptible to rising seas.

Before that, in a 2001 report, the International Panel on Climate Change, a group of world experts assessing the effects of warming, also said sea levels could rise up to 3 feet over the next century.

Earth's average temperature has increased about 1 degree Fahrenheit in the past 30 years, a relatively rapid rise, scientists say, and sea levels are rising about 1 inch each decade.

The difference between warming now and 129,000 years ago is that the ancient temperature increases were caused by deviations in the tilt of the Earth's axis and its orbital pattern, which affected the amount of sunlight warming the planet, said Bette Otto-Bliesner, a climate expert at NCAR and lead author of the other study.

Future warming is expected to be the result of carbon dioxide and other greenhouse gases emitted from vehicle tailpipes and smokestacks, she said.

The researchers projected increases in carbon-dioxide levels from today's 380 parts per million to 1,060 by 2100, a change forecast by the International Panel on Climate Change.

The researchers say that they used the mid-range of carbon-dioxide increases included in the IPCC 2001 report.

Based on that forecast, they say summer Arctic temperatures will jump by 4 degrees to 8 degrees Fahrenheit by 2100.

The studies, funded by the National Science Foundation, are among several recent reports that used satellite imagery, ice cores and geological records to measure the effects of warming.

A study last month by the National Aeronautics and Space Administration showed substantial melting of Greenland's glaciers, and a University of Colorado study published earlier this month found substantial melting in Antarctica.

The Goddard Institute of Space Studies released a report in January showing that last year was the warmest year on record. A NASA study released in September showed less sea ice floating in the Arctic Ocean than at any time in the past century.

The Bush administration, which has often been criticized for not taking enough steps to address warming, declined to discuss the newest studies.