Five years ago, a report called "Nation Under Siege" illustrated the vulnerability of 31 U.S. coastal cities to flooding. But not just to any kind of flooding -- to the flooding of a permanent kind from sea level rise.

What will happen to these cities, the report asked, as sea levels continue to increase from global warming? The study provided answers in a series of 3-D maps constructed using data from federal science agencies and the United Nations' climate panel. The maps provide an uncanny prediction of what happened last week when Sandy engulfed 1,000 miles of Atlantic coastline.

Most striking is a map of New York that shows what could happen with a 9.8-foot rise in sea level: Lower Manhattan, the East Village and the FDR Drive underwater. That's exactly what Sandy's storm surge delivered. Was superstorm Sandy a preview of what sea level rise will bring -- permanently -- to New York and other coastal cities by century's end? "This was essentially what we thought of as the once-in-a-100-years event," said Radley Horton, a NASA scientist specializing in climate projections at the Center for Climate Systems Research at Columbia University. "As sea levels rise, we'll see these types of events more often."

According to figures from the U.N. Intergovernmental Panel on Climate Change, oceans have risen on average by about 7 inches since 1900. And a report by the New York State Sea Level Rise Task Force said sea levels along New York's coast have increased 9 to 11 inches in the past century. And consequences of rising seas would reach far beyond those 31 cities, climate experts have warned. More than 50 percent of the U.S. population lives in coastal areas. A 2011 University of Arizona study identified 180 U.S. cities that would be at risk from rising sea levels. Said Horton: "I hate to say there's a silver lining, but if there's any positive it's that we can use this to learn and get a better opportunity to prepare for the future."