Sandy’s Wake

Columbia scientists have long been sounding the climate-change alarm. Will we listen now?

by Paul Hond Published Winter 2012-13
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“By the 2020s, because of sea-level rise, the defense will be good for a one-in-a-thousand-year storm. By the end of the century, it will be good for a one-hundred-year storm. So they have decided to not necessarily raise the levees, except in a few places, but to harden them, so that the water can overtop the levees and dikes without eroding them. That way, the whole ocean doesn’t come in, only the water that goes over.

“They will now rezone their terrain behind the dikes and levees to build catch basins, green parks, and soccer fields to absorb the water. Behind this they will raise their cities — they are building entire city blocks practically on barges that go up and down with the tides in those catch basins. Where there is old infrastructure and old cities, like in Rotterdam and Amsterdam, they internally secure them.

“They take a very integrated approach, and I think New Amsterdam should learn from Old Amsterdam. I want a sustainable New York City, not one that’s doomed two hundred years from now.”

A Strange Turn

It was one of the most destructive natural events in recorded history. On August 26 and 27, 1883, the fuming volcanic island of Krakatoa, located between the islands of Sumatra and Java in what is now Indonesia, erupted in earnest. The explosions were heard two thousand miles away in western Australia. Shock waves circled the globe seven times. Black ash shot fifty miles into the sky. Ash and stones rained down, killing hundreds. Chunks of the shattered island collapsed under the sea, triggering tsunamis that flooded coastal villages. The Dutch colonial government blamed the tsunamis for most of the 37,000 deaths linked to Krakatoa.

The eruption also changed the weather. Sun-blocking ash caused global temperatures to cool. There were blood-red sunsets and green moons. But weather followers noticed something else in the sky: clouds of high-altitude volcanic dust moving at high speeds. The patterns indicated previously unknown wind currents in the upper atmosphere. These winds would become known as the jet stream.

Radley Horton has his eye on that ribbon of west–east wind. A normal jet stream, he says, would have blown Sandy out to sea; instead, the jet stream was weak, with steep north–south dips. That weakness allowed the storm to stagnate over land.

In an office at the NASA Goddard Institute for Space Studies, on West 112th Street, Horton, who wrote the climate chapter of the 2011 ClimAID study, describes what made Sandy extraordinary: the nearly thousand-mile diameter of the tropical-storm-force winds that “got more of the Atlantic Ocean spinning than usual, so the surge was able to pile up”; its passing over water that was up to three to five degrees warmer than average; the timing of the surge with high tide; and the interaction with another storm passing west to east.

“New Amsterdam should learn from Old Amsterdam. I want a sustainable New York City, not one that’s doomed two hundred years from now.” — Klaus Jacob

“But the other element that’s interesting — and disturbing — is the unusual track the storm took,” Horton says. “Turning west after it was pretty far north. Normally, in late October, any storm that gets as far north as Delaware and New Jersey is generally going to get caught up in the jet stream, which by then is usually blowing strong. In this case, we had a meandering jet stream, very wavy, with a real kink in it that enabled the storm to take more of an east-to-west path.”

Horton has been investigating whether this wavier, weaker jet stream could be influenced by the loss of Arctic sea ice.

“We’ve lost about 70 percent of the volume of September sea ice compared to three decades ago,” he says. “No climate models, when you provide them the amount of greenhouse gases in the atmosphere over the last three decades, have been able to predict that rate of decline. That raises some questions: when the community does climate projections, are we capturing the full range of possible outcomes?

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