First, my sympathies to the folks in the Northeast who are
suffering from the after-effects of Hurricane Sandy. Watching CNN’s
breathless coverage of the flooding in New York and New Jersey, I
got intrigued by the question of sea level rise in those regions.
After all, one of the concerns about man-made global warming is
that there will be a significant increase in sea level over the
course of this century. The National Oceanic and Atmospheric Agency
actually offers this data online. Below are the charts for the
gauges at Battery Park in Manhattan and Atlantic City in New
Jersey.

The mean sea level trend is 2.77 millimeters/year with a
95% confidence interval of +/- 0.09 mm/yr based on monthly mean sea
level data from 1856 to 2006 which is equivalent to a change of
0.91 feet in 100 years.

The mean sea level trend is 3.99 millimeters/year with a 95%
confidence interval of +/- 0.18 mm/yr based on monthly mean sea
level data from 1911 to 2006 which is equivalent to a change of
1.31 feet in 100 years.

Even as sea levels around New York City have been rising, the
actual land area has been expanding due to landfilled areas. The
1865 Viele Water Map below shows the areas that had been filled in
by that time.

And below is a map of the area that the city government of New
York ordered to be evacuated – orange and yellow mark the areas
evacuated.

Some interesting correlations, yes? Instead of retreating from
the rising sea, people in New York City built up more land. Since
sea level rise is ongoing, and may be exacerbated by man-made
global warming, more and better defenses like a
sea barrier at the Verrazano Narrows and the East River will
need to be developed. One thing for sure, the federal government
should stop
subsidizing flood insurance. Go here for a
fascinating set of intereactive maps that show how the
shoreline of lower Manhattan has expanded since 1660.