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20 Big U.S. Cities that Should Worry About Sea Level Rise

By Alana Range

Sea level rise — we've heard about it, but what does it actually mean, and how will it affect you, and the community where you live?

Independent research has already predicted that by 2100, sea level may rise by one meter, due to a combination of the melting of land-based ice sheets and the warming oceans (when water warms, it expands). That gives us about 89 years until high tide is lapping at the door of many residents of Virginia Beach, New Orleans, and Miami, where some may need to find new homes on higher ground. But we already knew that.

A new study published by Climate Central's Ben Strauss and the University of Arizona's Jeremy Weiss and Jonathan Overpeck, takes a closer look at the problem of sea level rise. According to their research, rising sea levels could threaten an average of nine percent of the land within 180 U.S. coastal cities by 2100.

Of the 180 cities the study examines, 20 cities have populations above 300,000, and 160 cities have populations between 50,000 and 300,000. For each city, the scientists reported the percentage of the city's land under 1-6 meters in elevation (about 3-20 feet). Only cities directly connected to the sea were included. What did they find?

"Nationally on average, approximately nine percent of the area in these coastal municipalities lies at or below one meter. This figure rises to 36 percent when considering area at or below six meters."

An interesting aspect of this paper is that it factors in the amount of sea level rise we're "committing" ourselves to this century by maintaining our current output of greenhouse gases, such as carbon dioxide (CO2). With no change in our emissions, the paper suggests that we could see oceans rise as much as six meters in the coming centuries.

In the slide show above, we've found photos to represent the 20 largest cities likely to be affected by sea level rise, according to this study. In addition to the population of each city, we've included the percentage of land under the six meter elevation point.

For more on this study, read Ben Strauss' blog entry.