NEW YORK (AP) -- Flooded subways? A tornado in Brooklyn? It was tempting to blame it all on global warming.
Photo Gallery: Wild Storm Images
Plenty of public officials were doing just that in the aftermath of a short but violent thunderstorm that overwhelmed the city's drainage system, paralyzed the nation's largest mass transit network and tore the roofs off limestone townhouses.
"We may be dealing with meteorological conditions that are unprecedented,'' Metropolitan Transportation Authority Executive Director Elliot G. Sander said as his crews pumped millions of gallons of water from submerged train tracks.
The city's top water and sewer official, Department of Environmental Protection Commissioner Emily Lloyd, said the deluge may be evidence that the region is seeing an increase in the type of intense storm cells that used to roll through only once every five or 10 years.
Plenty of Brooklynites were thinking global warming, too. What else could be to blame for an honest-to-goodness twister in a borough where, historically, the closest thing to a cyclone has been a roller coaster on Coney Island?
The reality is not quite that simple, said weather and climate experts.
The storm that gathered strength over Pennsylvania, drenched New Jersey and then pounded the city at sunrise on Wednesday was strong but not particularly rare for a hot summer day, said Jeff Warner, a meteorologist at Pennsylvania State University. A similar storm drenched Pittsburgh early Thursday, he noted.
Climate scientist James Hansen, director of NASA's Goddard Institute of Space Studies, agreed: "You cannot blame a single specific event, such as this week's storm, on climate change,'' he said.
"However,'' he added, "it is fair to ask whether the human changes have altered the likelihood of such events. There the answer seems to be 'yes.'''
Storms, he explained in an e-mail to The Associated Press, are fueled by heat and moisture, and our atmosphere is becoming warmer and more humid.
And that, other experts said, has tended to mean more rain and rain that is more intense.
Nationwide, total rainfall and snowfall increased by about 7 percent during the 20th century, and the precipitation falling in the heaviest 1 percent of storms increased by 20 percent, said Jay Lawrimore, chief of the climate monitoring branch at National Oceanic & Atmospheric Administration's National Climatic Data Center.
"It is undeniable that the heavy precipitation events that create flash flooding are becoming more common,'' Lawrimore said.
Climate scientists generally measure weather changes in decades or centuries, not years, and across vast regions, not individual cities.
But New Yorkers could be forgiven for being suspicious that something about the weather has changed recently.
On July 18, a torrential storm similar to the one that struck Wednesday flooded roads, stranded some drivers in traffic jams for hours and forced a shutdown of some parts of the subway system. There also was mild subway flooding after a winter storm that played havoc with flights at the city's airports.
"This is supposed to be a rainfall event that is a once-in-a-decade occurrence -- we've had three in the past seven months,'' Gov. Eliot Spitzer said Thursday, after the tunnels had mostly dried out from the latest deluge. "We've got a serious issue to worry about.''
The DEP's Lloyd said the city is already preparing for a day when higher global temperatures mean wetter weather. It has been investing in better storm water pipes, urging developers to think more about drainage and drafting rules that might require parking lots to have rainwater-absorbing surfaces.
Mayor Michael Bloomberg also has unveiled plans to encourage public transit use as a way of slashing the pollution that contributes to global warming.
Cynthia Rosenzweig, a researcher at Columbia University and head of the Goddard Institute's climate impacts group, said more work may be needed. Wednesday's bad weather, she said, could turn out to be just a small dose of what lies ahead.
"This is just an absolute wake-up call to the city, and cities everywhere, to get ready,'' she said.
Photo of tornado damage in Bay Ridge from 1010 WINS' Mona Rivera.
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