Melting of polar ice and glaciers from a warming climate could create a new risk of flooding for New York City in the coming century, scientists are warning. "New York has become an urban experiment in the ways that seaboard cities can adapt to climate change over the next century," the Wall Street Journal reported on September 11 (" New York City Braces for Risk of Higher Seas," by Robert Lee Holtz). "For their part," writes Holtz, "the city's long-term planners are taking action but are trying to balance the cost of re-engineering the largest city in the U.S. against the uncertainties of climate forecasts."

Meltwater could raise sea levels by several feet around the planet by the end of the century, according to climate researchers. But the rise is not uniform — it depends on various factors, including the saltiness and temperature of the water. For New York's coastal waters, a rise of 20 inches could be in the cards by mid-century. While almost all of the city would still be above sea level, critical infrastructure — subways, power lines, and water and sewer pipes — would be at increased risk of flooding in a storm.

But that danger is not just in New York's hypothetical future, notes Holtz. A major hurricane making landfall at New York's harbor could bring a 30-foot storm surge and wreak havoc with many of the city's aging systems, not to mention its newer digital infrastructure. The Wall Street Journal offers a slideshow retrospective of the last hurricane to affect the city, 1999’s Hurricane Floyd, which brought rain, wind, and flooding — but no major surge — to the region.

City planners, notes Holtz, are walking a fine line as they weigh the cost of prevention against the risk of rising water. But the lessons of Hurricane Andrew’s devastating strike on Miami, and Katrina’s destructive flooding in New Orleans, can’t be far from the minds of city planners — and while the cost of prevention may be hard to bear, the cost of repairing the city after a direct hurricane strike is hard even to imagine.