By 2100, rising sea levels will threaten 9 percent of the land in coastal U.S. cities, according to a report released this month by the University of Arizona. Scientists there say the current rate of greenhouse gas emissions contributing to global warming — and increasing the earth's average temperature by 8 degrees Fahrenheit — continue to melt ice sheets, and sea levels will rise 4 to 6 feet over the next few centuries. The total population of potentially impacted cities and towns is 40 million people, and 20 of those locations hold more than 300,000 people. Nine big coastal cities, including New York and Boston, will face a potential 10 percent land loss — and so will New Orleans, according to the report.
Jeremy Weiss, senior research specialist at the university's Department of Geosciences, co-authored the study, which used U.S. Geological Survey (USGS) data to determine affected areas. The USGS data predates recent levee construction, though the city's levee systems are factored into the data. The report's maps show much of the city lying at or below 1 meter of elevation, with areas immediately along the Mississippi River (read: levee protection and higher ground) lying at or below 6 meters of elevation.
I think one of the main points that come out of our work (is) some municipalities will have a relatively large area potentially impacted, some will have a relatively small area potentially impacted," Weiss says.
The report doesn't offer any solution as to what needs to happen at the state and municipal levels to prevent those impacts, though its title ("Implications of Recent Sea Level Rise Science for Low-elevation Areas in Coastal Cities of the Conterminous U.S.A.") gives those governments a heads-up.
"Even though this is a global issue — the human cost to climate change, global sea level rise — the potential impacts from rising sea levels are very much a local phenomenon," Weiss says. "It's going to be different from location to location in the lower 48." — Alex Woodward