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.
A closer look at the lower Manhattan evacuation zones is below.
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.