Depending on geology, vulnerability, ocean currents and political leadership, some regions will be hit harder than others. Researchers recently discovered that the Atlantic coast between North Carolina and Massachusetts is a particular hot spot, with the sea rising three to four times faster than the global average. Among the U.S. cities most at risk:
New York City
Mayor Michael Bloomberg announced a $20 billion climate-protection plan, including the construction of Dutch-style levees and storm barriers to protect parts of the city from rising tides and higher storm surges. Bloomberg's plan is credible and far-sighted, but even if it's implemented, New York will remain massively vulnerable, especially low-lying areas of Queens and Brooklyn.
San Francisco/Silicon Valley
A recent study estimated that a three-foot sea-level rise would put $49 billion in property in the San Francisco Bay Area at risk of flooding, as well as 1,460 miles of roads, nine power plants and the region's airports. Also in trouble: headquarters of Silicon Valley icons like Facebook and Google, which sit by the edge of the bay and are protected by old levees that could easily fail.
The elaborate system of dikes and levees built to protect the city after Hurricane Katrina won't last for long. Most of New Orleans is already several feet below sea level; if a levee breaks in a hurricane, the city will be immediately flooded. In addition, the Mississippi River Delta is subsiding, making the job of protecting the city virtually impossible in the long run.
Built on the swampy shores of the Potomac River, the capital is highly vulnerable to rising tides and storm surges. Parts of Alexandria, Virginia, at the mouth of the Potomac, already flood at high tide. By the end of the century, the Atlantic may be crashing against the base of the Lincoln Memorial.
Much of Boston was created by filling in wetlands and estuaries. As the sea level rises and storm surges increase, those areas will be inundated first. Most at risk: the city's Back Bay neighborhood, Cambridge and Logan International Airport.
In 1900, 8,000 people were killed when a hurricane slammed into Galveston. The city built a sea wall to protect it, but today the land beneath Galveston is subsiding, and rising seas will inundate the city. A 2009 study estimates that with five feet of sea-level rise, 98,000 people will be displaced and $12.5 billion in property will be at risk. Gov. Rick Perry, a notorious climate denier, however, doesn't want to hear about it: In 2011, the Texas Commission on Environmental Quality, which is run by political appointees of Perry's, red-lined a report on sea-level rise in Galveston Bay, removing all mention of climate change.
Like New Orleans and Galveston, Norfolk is slowly sinking. During storms, flooding is so bad the mayor admitted parts of the city might soon be abandoned. Flooding threatens access to Naval Station Norfolk, the world's largest naval base.
Tampa/St. Pete, FL
Tampa’s problems are a lot like Miami's: a flat, low-lying city with lots of real estate along the water in hurricane country. Downtown Tampa, with its new convention center, is particularly vulnerable to rising seas.