MAPS: 3D Map | 2D Map Should a newly published sea level rise scenario come to pass, hundreds of American landmarks, neighborhoods, towns and cities would be submerged this century, at least in the absence of engineering massive, costly and unprecedented defenses and relocating major infrastructure. Ocean waters would cover land currently home to more than 12 million Americans and $2 trillion in property. See Mar A Lago below:
This extreme rise scenario, considered unlikely but increasingly plausible, was published together with other projections in a technical report by the National and Oceanic Atmospheric Administration in January. NOAA added “extreme” as a new sea level category in the publication, supplementing high, intermediate and low categories that have also been used in past reports. The new term reflects recent research suggesting that some parts of the Antarctic ice sheet may begin to collapse much sooner than scientists had previously anticipated, particularly if ongoing emissions of heat-trapping gases like carbon dioxide and methane remain high.
The extreme scenario would mean roughly 10 to 12 feet of sea level rise by 2100, depending on location, for all coastal states but Alaska — a significant departure above the global average projection (just over 8 feet). Detailed local projections are available from NOAA. http://sealevel.climatecentral.org/
Climate Central used NOAA’s localized extreme sea level projections, NOAA tidal models, and lidar-based (laser-based) land elevations to identify land that could fall below the high tide line in 2100. Low-lying areas that existing levees, ridges or other features appear to isolate from the ocean at this level were excluded. Coastal area population and property value data were overlaid against the remaining at-risk areas and totaled by city, state and nationally.
In more detail, we used the median sub-scenario of NOAA’s extreme scenario, and employed linear interpolation to create a continuous surface of projected sea level increments. We added these increments to local mean higher high water (MHHW) levels from NOAA’s VDatum model in order to map the projected high tide line in 2100. Because contemporary MHHW is evaluated across the national tidal epoch, which spans the years 1983-2001, we increased local sea level increments by roughly one inch in most cases, to account for rise from 1992 (the midpoint of the tidal epoch) to 2000 (the starting year for the NOAA scenarios). Population data came from the 2010 U.S. Census, and property value from an EPA coastal property database covering 2007-8 (Neumann et al. 2010). Strauss et al. 2012 describes the core methodology used for evaluating the exposure of density variables such as these, a methodology also employed extensively by Surging Seas Risk Finder.