Rising sea levels put dense cities at risk

WASHINGTON -- Nearly 4 million people across the United States, from Los Angeles to much of the East Coast, live in homes more prone to flooding from rising seas fueled by global warming, according to a new method of looking at flood risk published in two scientific papers.

The cities that have the most people living within three feet 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. The two big Southeast Florida counties, Miami-Dade and Broward, have 312,000 people at risk combined.

All told, 3.7 million people live in homes within three feet of high tide. More than 500 U.S. cities have at least 10 percent of the population at increased risk, the studies said.

"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.

The studies look at people who live in homes within three feet of high tide, whereas old studies looked just at elevation above sea level, according to work published in the peer-reviewed journal Environmental Research and an accompanying report by Climate Central. That's an important distinction because using high tide is more accurate for flooding impacts, said study co-author Jonathan Overpeck, a scientist at the University of Arizona's Institute of the Environment.

"It's shocking to see how large the impacts could be, particularly in southern Florida and Louisiana, but much of the coastal United States will share in the serious pain," Overpeck said.