Forbes magazine June 26, 2012
If you live close to the water on the East Coast of the United States, you might want to take a step or two back. Sea levels are rising around the world due to global warming. But according to a new study in Nature Climate Change, along the heavily-populated coastline from North Carolina to Massachusetts, they’re rising much faster than anywhere else:
U.S. Geological Survey scientists call the 600-mile swath a “hot spot” for climbing sea levels caused by global warming. Along the region, the Atlantic Ocean is rising at an annual rate three times to four times faster than the global average since 1990, according to the study published Sunday in the journal Nature Climate Change.
It’s not just a faster rate, but at a faster pace, like a car on a highway “jamming on the accelerator,” said the study’s lead author, Asbury Sallenger Jr., an oceanographer at the agency. He looked at sea levels starting in 1950, and noticed a change beginning in 1990.
Since then, sea levels have gone up globally about 2 inches. But in Norfolk, Va., where officials are scrambling to fight more frequent flooding, sea level has jumped a total of 4.8 inches, the research showed. For Philadelphia, levels went up 3.7 inches, and in New York City, it was 2.8 inches.
The study, by scientists from the U.S. Geological Survey, explains that sea level rise doesn’t happen uniformly: the rate of rise in any location depends on vast forces including ocean circulation, variations in temperature and/or salinity, and the rotation and shape of the earth. It also depends on the local topography of the coast, where land meets water.
The USGS scientists, using tide gauge data and computer modeling, believe that a combination of factors, including the pressures of favorable ocean currents, has actually suppressed sea levels for a time, but that time ended two decades ago, and now the trend is headed upward, much faster than elsewhere. For instance, the Intergovernmental Panel on Climate Change projects seas at New York City will rise 14 to 20 inches by 2100; the study’s authors estimate the accelerated rate could bump that up by 8 to 11 inches.
If it bears out, this is really bad news. Even a small increase in sea level can mean a lot more flooding in a storm, and more frequent floods than in the past. This is simple math, but it’s not something that governments have seriously grappled with.
The vast physical infrastructure along the East Coast is protected both by engineered systems, including floodgates, seawalls and levees, and by legal and economic systems, including zoning, building codes and flood insurance. For the most part, these are based on the assumption of stability: that things in the future will be like they were in the past. If water levels are rising, it requires a major rethinking about protecting what’s there and where and how to build in the future. Just ask people in New Orleans.
But in some places, the very notion that governments, private industry, and individuals might have to plan for this has provoked denial. The North Carolina legislature’s recent vote to prohibit the use of scientific projections of sea level rise in policymaking (now in a conference committee) looks increasingly foolish, as data accumulates that we’re not just dealing with 100-year projections but something that is already happening.