Global Warming in the News

Accelerating upward creep could reshape the coast and endanger Outer Banks, scientists say

RALEIGH.  Sea level on the N.C. coast could rise by as little as 1.2 feet to as much as 4.6 feet this century, potentially reshaping the state's beaches and inshore coastline, a panel of scientists and engineers reported Friday.

The broad range reflects the measurable upward creep of the Atlantic and the uncertainty of how far and how fast it will go. Globally, sea level rise has accelerated since the 1990s and that trend is expected to continue.

Panel members, whose findings concluded a two-day science forum, expect that the rise on the N.C. coast will continue at a moderate clip - about 4 millimeters a year - for another quarter-century. But that pace could accelerate later, scientists say, raising global seas 3 feet or more by 2100.

At that point, researchers say, the protective arc of the Outer Banks would be shattered, leaving vast Pamlico Sound virtually open ocean. Brackish wetlands that nurture much of the East Coast's young sea life could be drowned by saltwater. Some 2,300 square miles of low-lying land would be underwater or easily flooded.

Scientists say increasing storm activity and stronger waves, predicted under climate-change scenarios, will only magnify the effects of sea-level rise. North Carolina is among the states most vulnerable to rising seas, the National Oceanic and Atmospheric Administration says.

Coastal managers will use the estimates for planning, but they could widely affect the people who live and work in the 20 coastal counties. Local land management plans that include sea-rise projections, for example, could declare areas that are likely to flood off-limits to development.

Bob Emory of New Bern, chairman of the N.C. Coastal Resources Commission, said the projections aren't likely to result in dramatic policy changes soon.

Most residents believe North Carolina should take action on sea-level rise, according to a state survey of 1,100 people last year. Already, the N.C. Department of Transportation is beginning to weigh rising water as it designs coastal bridges and highways.

"Having to be out there planning things that will last 50 years or so is perhaps the most challenging aspect," said Margery Overton, an N.C. State University civil engineering professor who led the panel.

The panel recommended that the state add more monitoring stations and revisit its estimates every five years. Its report wrapped up a two-day forum organized by the N.C. Division of Coastal Management.

On the Outer Banks, rising seas aren't the biggest threat perceived by Nags Head officials. The town plans to spend $36 million to pump sand on its eroding beaches, where some houses have been undermined, and will continue an orderly retreat from the sea.

"It's an incremental change," said Mayor Bob Oakes. "We've been dealing with sea level rise for the past 100 years."

'The change is so dramatic'

Scientists who presented current research say global sea levels are likely to rise even higher than the Intergovernmental Panel of Climate Change's 2007 estimate of 0.6 to 2 feet.

Ice sheets in Greenland are shifting rapidly, and signs of unstable ice are emerging in western Antarctica, said Gordon Hamilton of the University of Maine. The ice sheets in Greenland alone could raise global seas some 20 feet.

"The change is so dramatic that we are rapidly reaching consensus at least in the glaciological community that sea level rise by 2100 is going be at least twice the upper boundary of the IPCC report," he said.

North Carolina is far ahead of most states because of its retinue of coastal scientists and accurate data useful in assessing risks, said Virginia Burkett, the U.S. Geological Survey's chief climate scientist.

Sea levels have been stable for more than 7,000 years but have risen at an accelerated rate in recent years, Burkett said, nearly doubling the 20th century rate between 1993 and 2003.

The rate of measured rise varies widely because of different geologic conditions. In the soft sediment of the northern coastline, it's 1.4 feet per century at Duck on the Outer Banks. It's about half that on the sand-covered rock on the southern coast near Wilmington.

In the same way, scientists say, rising seas will have varying effects on the N.C. coast. "You may see one thing one place and another thing another place," Overton said.

The panel's low-end projection, 1.26 feet, assumes that the pace of rise measured at Duck, considered the most reliable measuring point, continues steadily.

The middle number, 3.28 feet, is in line with the widely held expectation of about a 3-foot rise around the globe.

The highest figure, 4.59 feet, reflects growing views among climate scientists that oceans will swell even faster.

Adapting to a rising sea "is going to cost us. It's pay now or pay later," said David Knight, an assistant secretary of the N.C. Department of Environment and Natural Resources. "It's hard to think 80 to 100 years down the road, which is why it's important to incorporate it into long-term planning and let science lead on this."