"Our subsidized insurance market is an embarrassment to anyone who believes in free enterprise," said state Senator Alan Hays, a Republican on the Banking and Insurance Committee who lives in Umatilla, an inland city about 45 miles northwest of Orlando.

In Florida, where seven of the National Hurricane Center's 10 most expensive storms have hit, the insurance, mortgage and building industries have opposed changes to Citizens Property that would reduce the amount inland residents pay toward indemnifying their coastal neighbors.

Republican Governor Rick Scott, who owns a beachfront home in Naples, on the Gulf of Mexico, that he says the company doesn't cover, has championed the measures.

Opponents, such as Republican state Senator Mike Fasano of New Port Richey, say the measures would increase rates for his coastal constituents and damage the real-estate market.

"It's difficult for me to understand what the emergency here is," Fasano said. "If they raise premiums and there is no storm, where has that money gone? Will a homeowner see a reduction? Absolutely not."

High Water Everywhere

Climate Central's report will intensify the debate, Hunter said. The organization, started in 2008 with a Flora Family Foundation grant, also got money from Google Inc., the National Aeronautics and Space Administration and other government agencies and nonprofit groups, according to its Web site.

The study, led by Ben Strauss, is based on 2010 census data and land-elevation estimates from the U.S. Geological Survey and NASA. The study also calculated estimates for how global warming shifts the odds of high storm surges.

The conclusion is that sea level is rising at an accelerated rate that "dramatically increases" the odds of the worst floods, according to the report.

Florida, where about 2.4 million people live within four feet of the local high-tide line, has eight of the 10 U.S. cities most at risk, according to Climate Central's study.

Florida Deluged

About $30 billion in taxable property is endangered in just three southeast Florida counties, excluding Miami-Dade, which has the most homes at risk in the state and the nation, according to the report.