Mar. 30, 1998 Global warming will make the New York metropolitan region not only warmer, but wetter as well, according to a new Columbia University study.
Subways, airports and low-lying coastal areas could experience flooding if global warming produces more violent storms and higher sea levels, as expected, said Vivien Gornitz, associate research scientist at Columbia's Center for Climate Systems Research. Local temperatures could rise by as much as four degrees Fahrenheit, and sea levels could increase by up to eight inches by 2030 and by as much as four feet by 2100, under the most extreme scenarios, she said.
Dr. Gornitz presented the new work at the Metro East Workshop, held March 23-24 at Columbia, one in a series sponsored by the federal government to assess regional vulnerability to climate change. The results, with reports from 18 other regions, will be presented to Congress and the president by 2000.
Dr. Gornitz, who is also affiliated with the National Aeronautics and Space Administration's Goddard Institute for Space Studies, was joined by co-authors Cynthia Rosenzweig, adjunct research scientist at the Center for Climate Systems Research; Chris Small, associate research scientist at Columbia's Lamont-Doherty Earth Observatory; Richard Goldberg, research staff assistant at the center, and David Rind, adjunct senior research scientist at Lamont.
Dr. Gornitz presented three scenarios for the period 1995 to 2030: a low-change scenario that is her extrapolation of current trends without any greenhouse-induced warming; a middle ground, based on simulations from the Geophysical Fluid Dynamics Laboratory at Princeton University, and a high- change scenario developed at the Goddard Institute, called Business as Usual,that assumes greenhouse warming takes place without any mitigating efforts. Temperatures in the metropolitan area increase over the period by one to four degrees Fahrenheit, according to the models. None of the scenarios finds significant increases in precipitation.
But all the scenarios show local sea-level rises, ranging from four to eight inches by 2030, and maximum coastal flood heights of nearly six feet, an increase of nearly a foot from current levels. That means that any area below six feet above sea level would be vulnerable to flooding, including most of the lower Manhattan shoreline, coastal and island areas of Jamaica Bay, much of downtown Hoboken and Jersey City and south shore beaches in Staten Island and the Rockaways.
About an inch of the sea-level rise is really a ground-level fall, Dr. Gornitz said. The northeastern United States is dropping by about one millimeter a year, offsetting a rise in southern Canada, which was previously compressed by glaciers. Local geological factors elsewhere may mitigate rising sea levels.
Scientists and policymakers may quibble over details, but when all models show significant sea-level rises, it's time to pay attention, Dr. Gornitz said. "Obviously, the best mitigating action would be to reduce greenhouse gases, but that is proving to be extremely difficult, because many countries must agree to limit their emissions," she said.
State and local planners should be thinking about countermeasures now, Dr. Gornitz said. Areas that are just above sea level, including parts of lower Manhattan and New Jersey, could be protected with seawalls. Runways at Kennedy, LaGuardia and Newark airports could be raised above expected flood levels. Pumping systems may be needed to keep the New York City subways dry, and some coastal roadways, such as the West Side Highway, may need to be moved inland, she added. The Columbia scientist called for rezoning of coastal areas for parks and recreational uses, not high-density residential development.
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