Nearly 4 million people across the nation live in homes more prone to flooding from rising seas fueled by global warming, according to new research in two scientific papers.

"Southeast Florida is definitely the highest density of population that's really on low coastal land that's really most at risk," said lead author Ben Strauss, a scientist at Climate Central. Climate Central is a New Jersey-based group of scientists and journalists who do research about climate change.

But Louisiana, California, New York and New Jersey are also particularly vulnerable, researchers found, and virtually the entire U.S. coastline is at some degree of risk.

The cities that have the most people living within three feet (one meter) of high tide — the projected sea level rise by the year 2100 made by many scientists and computer models — are in Florida, Louisiana, and New York. New York City, often not thought of as a city prone to flooding, has 141,000 people at risk, which is second only to New Orleans' 284,000.

Sea level has already risen about 8 inches since 1880 because warmer waters expand, Strauss said. In addition to the basic physics of ever-warming water expanding, scientist say hotter climate will cause some melting of glaciers in Greenland and western Antarctica that would then cause seas to rise even more.

Flooding from Hurricane Irene last year illustrated how vulnerable coastal places such as Manhattan are with a combination of storms and sea level rise, according to Strauss.

Using data from the latest census, Climate Central also has developed an interactive system that allows people to check their risk by entering a ZIP code.  http://sealevel.climatecentral.org/