A recent National Aeronautics and Space Administration report yet again raises alarm that New Yorkers are about to be inundated by rapidly rising seas. But a review of the data suggests that such warnings need to be taken with more than a few grains of sea salt. The record of sea level measured at the southern tip of Manhattan, known as the Battery, begins in 1856. It shows that today’s waters are 19 inches higher than they were 166 years ago, rising an average of 3.5 inches every 30 years. The geologic record shows that this rise began some 20,000 years ago as the last great glaciers melted, causing the New York coastline to move inland more than 50 miles.

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