Sea Levels Could Rise by 23 Feet by 2100, Researcher Writes

Nearly 1,500 municipalities could find themselves mostly submerged during high tide before the end of the century if global climate emissions continue to increase, a new paper published in the Proceedings of the National Academy of Sciences argues.

The report, written by Ben Strauss, the vice president for Climate Impacts and director of the Program on Sea Level Rise at Climate Central, is an analysis of an earlier study published in the same journal in which scientists found that for every degree Fahrenheit of global warming due to carbon pollution the global average sea level will rise an estimated 4.2 feet in the long run.

This, Strauss explains, is because while current measurements indicate the sea level is currently rising by 1 inch per decade, it is accompanied by "an invisible shadow process" that "carbon emissions and warming have locked in for later years."

According to the study led by Anders Levermann, a climate scientist at the Potsdam Institute for Climate Impact Research, this "lock in" amounts to 4.2 feet per degree Fahrenheit in the long run.

"When multiplied by the current rate of carbon emissions, and the best estimate of global temperature sensitivity to pollution, this translates to a long-term sea level rise commitment that is now growing at about 1 foot per decade," Strauss said.

To start with, 4 feet of sea level rise past current levels appears to have already been locked in based on the amount of carbon pollution to date, the researcher explains -- enough to submerge more than half of today's populations in 316 coastal cities and towns in the lower 48 states.

Furthermore, should global emissions continue to increase, the world could see 23 feet of locked in sea level rise by the end of the century, putting some U.S. 1,500 communities at risk of becoming more than half submerged during high tide. 

On the other hand, in the case of a "very low emissions scenario," Strauss estimates that just 555 coastal communities, versus 1,500, will find themselves under a similar threat.

In coming to these numbers, Strauss explains that he combined his sea level debt findings with an analysis from Climate Central's Surging Seas project, a national assessment and mapping of coastal vulnerability based mostly on elevation and census data.

What this does not take into account, however, is any kind of engineering, which Strauss says could prove to increase inhabitable area despite being below sea level, as seen in New Orleans.

Most vulnerable overall, however, is southern Florida, which Strauss warns faces a sharp rise under any emissions scenario that, due to the porous bedrock underlying it, "will be very difficult to protect."

For an interactive map detailing Strauss' findings, click here.