Heat waves will get longer and more intense, IPCC says, and the frequency of heavy precipitation events and other major storms will increase over the 21st century in many places. "It is virtually certain that increases in the frequency of warm daily temperature extremes and decreases in cold extremes will occur throughout the 21st century on a global scale," says a summary of the report.
A few months ago, just as Hurricane Irene was bearing down on New York City, PM wondered about the risk to cities, especially coastal ones, and severe weather events worsen. This article begins with a thought experiment into what would happen if a major hurricane did strike New York at full strength, but the lessons about disaster preparation apply far beyond the Big Apple.
The hurricane churning east of New Jersey seems destined for the mid-Atlantic. Then a cold front descending out of Canada nudges the Category 2 storm northwest instead?setting it on a worst-case course for New York City.
New York Harbor has often sheltered the city, dissipating energy from violent gales that start at sea. But now it plays an opposite role: It turns an otherwise moderate hurricane into a disaster. As the eye of the storm passes over Staten Island, the 100-mph counterclockwise winds shove 500 million tons of seawater directly into the harbor. The narrowing shorelines and shallowing sea bottom cause the mass of water to build. By the time the storm surge washes over the shores of Brooklyn, Queens and Manhattan, it towers 11 to 15 feet high.
Water flows through New York's financial district and reaches 2 miles into southern Brooklyn and Queens, flooding 2900 miles of roads. Impromptu rivers gush into subway stations and pour through hundreds of sidewalk gratings.
In Manhattan, the lower levels of Penn Station and Grand Central fill with water. The subway floods within 40 minutes?paralyzing the city's chief form of public transportation. Three of the four automobile tunnels linking Manhattan to the outer boroughs and New Jersey also flood, submerging hundreds of cars stranded in traffic jams during evacuation. A million people lose electricity and phone service as floods shut down 10 power plants and the emergency generators powering cellphone towers.
While this scenario may sound like yet another apocalypse-in-New York summer blockbuster, it was produced using calculations from the U.S. Army Corps of Engineers?and it's been given serious attention from government planners. That 1995 Army Corps report and a 2006 analysis by the Department of Homeland Security predict that a Category 4 hurricane scoring a direct hit on New York City would inflict $500 billion worth of damage?quadruple that wrought by Category 5 Hurricane Katrina in 2005.
A third study, released this September by New York state, predicts that an even milder, Category 1 hurricane or winter nor'easter could inundate the city's subway and cause $58 billion in losses. Experts don't consider such disastrous flooding a mere possibility; they believe it's a certainty?a one-in-100-year event. Sea level rise will upgrade it to a one-in-35-year event by 2080.
"We've been very, very lucky because we haven't had that [direct hit]," says Cynthia Rosenzweig, a climate-impact scientist at the NASA Goddard Institute for Space Studies in New York who has helped guide the city's storm- and climate-?planning effort. "But the potential vulnerability for that is very high."
New York City
According to the Metro New York Hurricane Transportation Study, an analysis by the U.S. Army Corps of Engineers, a Category 4 hurricane could inflict $500 billion worth of damage. SLOSH computer models from the city's Office of Emergency Management show that a direct hit by even a Category 2 storm would completely inundate Rockaway Peninsula; a Category 3 storm would put JFK airport under 19 feet of water.
Every region of the U.S. is subject to catastrophic storms of one type or another. While the severe floods and tornadoes that devastated large swaths of the country this spring surprised many people, there's no reason they should have. Annual losses from natural hazards have increased severalfold over time?costing the nation $573 billion in crops and property since 1960. Americans are turning even routine storms into full-blown disasters by settling where they strike. Then, when vulnerable infrastructure is swept away, people have exhibited a steadfast commitment to rebuilding it.
"There are more people living in what we might consider to be high-hazard areas," says Susan Cutter, a disaster scientist at the University of South Carolina in Columbia. These include coastal areas, floodplains and places especially prone to tornadoes and landslides. By 2040, 70 percent of the U.S. population?which should then number 400 million?is expected to concentrate in 11 megaregions, seven of which occupy coastal counties.
If New York?part of the Northeast megaregion?suffers a direct hit, workers will spend weeks pumping a billion gallons of brackish water out of its subway and train tunnels. The salt will corrode power lines, transformers and thousands of brakes and switches that control the trains. Some subsystems could take a year or more to restore.
To avoid such a scenario, New York state recommends the city invest well over $100 million a year in storm protections. City planners are already experimenting with dozens of low-tech fixes, says Adam Freed, deputy director of the Mayor's Office of Long-Term Planning and Sustainability. These include raising subway vents above sidewalks, installing several-inch-high barriers around subway entrances and using porous pavement. They've also considered building lips around rooftops to slow the percolation of water into streets and sewers, because every inch of rain that falls on New York translates to a billion gallons of storm water that must be managed.
Some observers, such as Malcolm Bowman, an oceanographer at the State University of New York at Stony Brook, have even suggested that four massive barriers be built across the waterways surrounding the city. The arms would swing shut during severe storms?much like those of the Maeslantkering, a barrier that protects the Port of Rotterdam from surges in the North Sea.
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