Climate change could cause unprecedented hurricanes to pound New York City and other coastal cities over the next hundred years, according to new research by scientists at Princeton University and the Massachusetts Institute of Technology.
Sea level rise and warmer water temperatures could potentially cause "a storm the likes of which have not been seen," says Michael Oppenheimer, a geosciences professor at Princeton. A one-meter sea level rise, which scientists expect by 2100, would greatly increase the frequency of so-called "storms of the century," which could occur closer to every 10 years if sea level rise isn't stopped, the research says.
The team simulated storm surges, which are temporary rises in the sea level associated with offshore cyclones and winds that often occur during hurricanes. A storm surge during Hurricane Katrina raised put parts of New Orleans under more than 14 feet of water.
According to climate prediction models, in 2100, storm frequency could increase by as much as 290 percent, although one of the models actually projected a 15 percent decrease in storm frequency.
Under Oppenheimer's worst-case scenario, a hurricane the size of the one that hit New York City in 1821—which buried Manhattan under 10 feet of water—would have to strike at high tide. In the Princeton simulation, a storm of that magnitude could put Manhattan under more than 15 feet of water. Manhattan's current sea wall is just five feet tall, which, even under present conditions, makes it "highly vulnerable to extreme hurricane-surge flooding," the report says.
Hurricanes that actually make landfall on Manhattan are rare. Before last year's Hurricane Irene, which produced a storm surge of just over four feet, a hurricane had not hit the city since 1893.
"Last time there was anything close to [the worst-case scenario], Manhattan wasn't particularly built up," Oppenheimer says, so the 1821 storm wasn't particularly destructive. Although the team simulated potential storms that would hit lower Manhattan, any city that is at or near sea level is likely to experience more frequent storms. According to the report, "climate change will probably increase storm intensity and size simultaneously, resulting in a significant intensification of storm surges."
There is already some evidence to support the fact that hurricanes are becoming both more frequent and more intense. The American Meteorological Association wrote in a 2007 report that "a growing body of recent scientific work suggests that hurricanes have become more intense over the last several decades." According to estimates by NASA, temperatures on the surfaces of tropical oceans have increased by nearly 1 degree Fahrenheit over the past 100 years.
Oppenheimer hopes the research will give city planners "ample opportunity to prepare" for big storms. In some places, that means building higher levees and sea walls. In others, it means creating "buffer zones" between the shore and buildings.
"It's difficult [to redesign cities]. But look, cities evolve. We're talking about a 100 year time scale—there's time to consider our options," he says. "There's so much property and so many lives at stake."