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How the Seas Will Eat Coastal Cities

(Flooding in New Orleans after Hurricane Katrina, by NOAA)

The answer is: “At least two feet, and possibly as much as seven.”

That’s the estimate of how much the oceans can be expected to rise by the year 2100 if we don’t take immediate and urgent action to curb greenhouse gas emissions.

The results are from a study by Climate Central. And while we simply don’t know whether we’ll escape with just two feet or be washed away by a seven-foot increase, either way it’s really bad news for our coastal cities. According to the report:

Global warming has raised global sea level about 8 inches since 1880, and the rate of rise is accelerating. Rising seas dramatically increase the odds of damaging floods from storm surges. A Climate Central analysis finds the odds of “century” or worse floods occurring by 2030 are on track to double or more, over widespread areas of the U.S. These increases threaten an enormous amount of damage. Across the country, nearly 5 million people live in 2.6 million homes at less than 4 feet above high tide — a level lower than the century flood line for most locations analyzed.

In other words, in just a few decades from now, thousands of people who live in cities like New York, Boston, Washington DC, Miami, New Orleans could be doing what the residents of the Kiribati in the South Pacific are doing today: looking for somewhere else to live.

In this map, you see Miami with just two feet of sea-level rise. The white areas bordered in blue are what remains of dry land.

With a seven-foot rise, there’s basically nothing left:

The situation will be similar in other coast cities.

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

“It’s shocking to see how large the impacts could be, particularly in southern Florida and Louisiana, but much of the coastal U.S. will share in the serious pain,” said study co-author Jonathan Overpeck, a scientist at the University of Arizona’s Institute of the Environment.

The study by Climate Central includes interactive maps, so you can enter your own zip code and see how your home may be affected.