On December 11, 1992, a powerful northeaster coalesced off the eastern seaboard of the United States, and an eight-foot storm surge struck New York City. Seawater swamped the Brooklyn Battery Tunnel to a depth of six feet, cascaded down PATH subway stairs in Hoboken, NJ, and forced LaGuardia Airport and many roads and subways lines to close. Had the storm been slightly stronger, a 10-foot surge could have devastated a far wider region, inundating low-lying areas like Coney Island and Manhattan’s financial district and overwhelming the 14 sewage plants dotting the New York City coastline.
A flood of comparable height in New York City’s environs should occur about once every 100 years, on average, in the estimation of one Columbia University study. But global warming and rising sea levels–as well as the possibility of more-intense precipitation, stronger storms, and altered storm trajectories–will make such disasters more frequent. And to protect the people who live and work where disaster threatens, the critical first step is to determine how quickly and by how much, exactly, the threat is increasing. That knowledge is essential to deciding how seriously to consider specific countermeasures; for New York, these could range from mandatory evacuation plans for seaside neighborhoods to multibillion-dollar storm-surge barriers spanning the Verrazano Narrows and other key channels.
But there are no clear answers, and part of the problem is that well-documented predictions about planetary change haven’t generally been broken down in local terms. Though the Intergovernmental Panel on Climate Change (IPCC) has concluded with 90 percent certainty that human activity is warming the planet–and spelled out the likelihood of consequences that include higher seas, droughts, and fiercer storms–the United States is committing scant resources to providing usable information to the people who respond to emergencies, plan for urban development, manage coastal areas, and make sure the crops keep growing and the reservoirs stay full. “The challenge is to increase our capability to accurately forecast climate at the regional level,” says Ronald Prinn, an atmospheric scientist who directs the Center for Global Change Science at MIT. “That is what is needed in order to improve the information that government agencies get–[and] to then translate those regional forecasts into something useful at the city [or] state level.” Equipping people to deal with climate change could mean simply giving state and local planners access to a wealth of existing information–such as calculations made by the National Oceanic and Atmospheric Administration (NOAA) that could indicate how far inland storm surges would move if sea levels were higher. But it will also mean sharpening local and regional models, so that they can predict the effects of climate change in far greater geographic detail. And it will require new approaches to emergency planning, water-supply management, and more.