Two reports that came out today warn that sea levels on both the East and West coasts of the US are rising much faster than expected.
California's sea levels could be a foot higher in the next 20 years, two feet higher by 2050 and over five feet higher by the end of this century, according to a National Research Council report. Levels are forecast to be highest south of Cape Mendocino.
That would threaten homes, ports, highways and airports along the coast.
"As the average sea level rises, the number and duration of extreme storm surges and high waves are expected to escalate, and this increases the risk of flooding, coastal erosion and wetland loss," says Robert Dalrymple, chair of the committee that wrote the report and a professor of civil engineering at Johns Hopkins University.
Sea level rise in Oregon and Washington is expected to be more modest because the land is also rising.
The study was commissioned by states and federal agencies to the National Research Council, which is a nonprofit that provides scientific information for government decision-makers under the auspices of the National Academy of Sciences, the National Academy of Engineering and the Institute of Medicine.
Sea levels on the East Coast, from North Carolina to Boston, are rising much faster than the rest of the world, according to the US Geological Survey.
The Atlantic Ocean in that area has been rising 3-4 times faster every year than the global average since 1990, reports a study published in Nature Climate Change.
"It's not just a faster rate, but a faster pace, like a car on a highway jamming on the accelerator," says lead author, Asbury Sallenger, an oceanographer who has analyzed sea levels starting from 1950, told the Associated Press.
Since 1990, global sea level are around 2 inches higher, but they are 4.8 inches higher in Norfolk, Virginia, which is experiencing more frequent floods. Sea levels in New York City are up 2.8 inches, and in Philadelphia, 3.7 inches.
Computer models have long projected higher sea levels on the East Coast because of changes in ocean currents from global warming - this is the first study that demonstrates it's already happened.
Scientists say that global warming is causing the Gulf Stream to slow down, which changes the slope of the ocean.
By 2100, computer models project rises to 3.3 feet globallly, and 8-11 inches more on the East Coast.
These estimates recently came to a head in North Carolina, when Republican legislators proposed using historic sea levels of 12 inches, instead of foward-looking ones calculated by scientists, to create flood maps that affect property development and flood insurance rates.
Many coastal studies experts think a level of 5 to 7 feet should be used, since states typically plan for the plausible worst-case scenario, especially with expensive, long-lived infrastructure.
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