Benjamin Strauss and Robert Kopp write: The oceans have risen and fallen throughout Earth’s history, following the planet’s natural temperature cycles. Twenty thousand years ago, what is now New York City was at the edge of a giant ice sheet, and the sea was roughly 400 feet lower. But as the last ice age thawed, the sea rose to where it is today.

Now we are in a new warming phase, and the oceans are rising again after thousands of years of stability. As scientists who study sea level change and storm surge, we fear that Hurricane Sandy gave only a modest preview of the dangers to come, as we continue to power our global economy by burning fuels that pollute the air with heat-trapping gases.

This past summer, a disconcerting new scientific study by the climate scientist Michiel Schaeffer and colleagues — published in the journal Nature Climate Change — suggested that no matter how quickly we cut this pollution, we are unlikely to keep the seas from climbing less than five feet.

More than six million Americans live on land less than five feet above the local high tide. (Searchable maps and analyses are available at SurgingSeas.org for every low-lying coastal community in the contiguous United States.) Worse, rising seas raise the launching pad for storm surge, the thick wall of water that the wind can drive ahead of a storm. In a world with oceans that are five feet higher, our calculations show that New York City would average one flood as high as Hurricane Sandy’s about every 15 years, even without accounting for the stronger storms and bigger surges that are likely to result from warming. [Continue reading…]