Echoes of Superstorm Sandy remain from Manhattan's once-flooded
streets to Maryland's battered boardwalks to New Jersey's washed-away
No surprise. The Eastern Seaboard - or any coastal region
- occasionally finds itself in the cross hairs of ferocious ocean
storms. But it may have taken Sandy to drive home the added threat that
scientists have been warning about for years: a rise in the sea level.
of the same could lie ahead, suggest ocean scientists such as U.S.
Geological Survey oceanographer Asbury Sallenger. The storm triggered
the expected arguments about global warming's role, but that debate
aside, the new constant for any storm is the increasingly important role
likely to be played by sea level. In a study out Tuesday, climate
scientists led by Stefan Rahmstorf of Germany's Potsdam Institute report
that since 1993 sea level has risen worldwide at a rate 60% higher
than predictions. The findings appear in the Environmental Research Letters journal.
rise is accelerating along the East Coast," Sallenger says. "Every inch
adds to the kind of inundation we saw in Sandy."
question, Sallenger and other ocean experts say, is what effect rising
sea levels, which are accelerating along a "hotspot" stretching from
Cape Hatteras, N.C., to Maine, will have on storms hitting these places.
In June, Sallenger and colleagues reported in the journal Nature Climate Change
that sea-level rise along the U.S. Atlantic Coast has been climbing at a
rate three to four times higher than the global average since 1950.
About 1.5 inches per decade now, it doesn't sound like a lot. But each
inch counts, and New York Harbor's water level is 11 to 16 inches higher
than it was a century ago, Sallenger says.
sea-level rise springs partly from "subsidence," where groundwater
withdrawals to sate thirsty towns and farms along the coast cause the
ground to sink, and partly from warming waters in the North Atlantic,
the study suggests. Warmer water simply takes up more space than cold
Not to be forgotten is that teetering infrastructure poses as much of a problem as global warming, says Alan Weisman, author of The World Without Us.
"This is just one storm. People shouldn't lose sight of the fact that
cities around the world have been flooding," Weisman says, referring to
inundations in Manila, Bangkok and New York over just the past two
years. "The politicization of this reality has been disconcerting, and I
hope it stops, but I'm not hopeful."
Most climate scientists
would see Superstorm Sandy as a largely natural event, not something
born as a result of global warming, says Texas Tech climate researcher
Katharine Hayhoe. But she acknowledges that the storm, sea-level rise
and climate change are hard to disentangle.
A water level that's a
few inches higher pales in comparison with a 14-foot storm surge in
Lower Manhattan, but those few inches meant the surge was higher than it
might have been otherwise.
And was the storm surge stronger
because of climate change? Indeed. Warmer ocean temperatures could have
provided up to 20% greater power for the storm, so climate change's role
isn't necessarily an either-or question, Hayhoe says.
"It is exactly two sides of the coin, and I think we'd both see the same two sides," she says.
climate projections that look ahead to the coming century see
hurricanes that look stronger, but are fewer in number. Why? Warmer
waters strengthen storms but stronger winds above the equatorial oceans
wreck the stillness that burgeoning tropical storms need to become
"While we do expect increased hurricane
damage in the U.S. as the climate warms, Sandy is not a pure example of a
hurricane," says MIT hurricane expert Kerry Emanuel. It was a hybrid
event that started as a tropical storm, grew into a hurricane, and
morphed into an intense nor'easter. He says climate science doesn't have
enough data to say whether these hybrid storms like Sandy will become
more or less frequent.
It also doesn't matter, Emanuel writes in the current Foreign Policy magazine, because the real problem is sea-level rise.
2007 Intergovernmental Panel on Climate Change estimated that warming
alone, which expands ocean waters, would raise sea levels worldwide by
almost two feet over the next century. Add in future melting glaciers
in Greenland and elsewhere, and sea level could rise more than 3 feet by
then, NASA climate scientist James Hansen and Stanford's Ken Caldeira
reported at last year's American Geophysical Union meeting in San
"The whole point is that we see it accelerating,"
Sallenger says. While the "hotspot" study suggests this worsening will
continue, he acknowledges other researchers are taking a more
"Geologic records show that sea-level rise happens in big spurts, stops and starts," Sallenger says.
Also worth noting, a 2009 study led by Environmental Protection Agency
analyst Jim Titus concluded that 60% of the East Coast's coastal land is
zoned for more development, while less than 10% is zoned for wetlands
that soak up storms.
"We have to rethink these flood heights to be
more like 'Every year your chance of flooding is 1%,' rather thinking
it won't happen for another 100 years," says urban flooding expert
Jeroen Aerts of Vrije University in Amsterdam. "I'm from Amsterdam, and I
walk around New York seeing all this land exposed without a sea wall,
and I'm just shocked."
At the same time, dikes, or seawalls, are
an unlikely remedy for the entire East Coast, says civil engineer Robert
Traver of Villanova (Pa.) University. Of the 25 most-densely populated
counties nationwide, 23 are coastal ones. "We can't build barriers
around everything," Traver says.