How Global Warming Made Hurricane Sandy Worse

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It makes me a little nuts when people insist because they can't draw a direct line between global warming and extreme weather, because they really don't understand how it actually works. This Mother Jones piece does an excellent job of explaining the connection:

Superstorm Sandy—and its revival of the issue of climate change, most prominently through Michael Bloomberg's sudden endorsement—probably aided President Obama's reelection victory last night. But at the same time, there has been a vast debate about the true nature of the storm's connections to global warming (as well as plenty of denialism regarding those connections). In fact, there has even been the suggestion, by cognitive linguist George Lakoff, that if we all stopped thinking about causation as something direct (I pushed him, he fell) and rather as something systemic (indirect, probabilistic), then we really could say with full accuracy that global warming caused Sandy. Systemically.

Following this debate, I've been struck by the strong impression that people are making things too complicated. Here's the simple truth: Leaving aside questions of systemic causation—and sidestepping probabilities, loaded dice, atmospheres on steroids, and so on—we can nevertheless say that global warming made Sandy directly and unmistakably worse, because of its contribution to sea level rise.

"I keep telling people the one lock you have here is sea level rise," meteorologist Scott Mandiaexplained to me recently. "It's the one thing that absolutely made the storm worse that you can't wiggle out of."

Mandia is an expert on the subject at Suffolk County Community College, and coauthor of the new book Rising Sea Levels: An Introduction to Cause and Impact.

And how do we know Mandia is right? Here's the logic.

First, according to sea level expert Ben Strauss of Climate Central, the sea level in the New York harbor today is 15 inches higher than it was in 1880. Now, to be sure, not all of that is due global warming—land has also been subsiding. Strauss estimates that climate change—which causes sea level rise both through the melting of land-based ice, and through thermal expansion of warm ocean water—is responsible for just over half, or eight inches, of the total. As it happens, the estimated sea level rise seen globally since the year 1880 is also roughly eight inches.

So how, then, did global warming directly make Sandy worse? Simple: Sandy threw the ocean at the land, and because of global warming, there were about eight inches more ocean to throw. "The footprint of the flood was bigger, based on roughly eight extra inches of depth," Strauss explains—eight inches more than there would have been in an admittedly hypothetical world in which Sandy arrived without our burning of fossil fuels or heating of the atmosphere.

[...] Consider the US Army Corps of Engineers' "depth-damage" functions, which the Corps uses to study how much flood damage grows with an increasing water level. The upshot here, says Mandia, is that "the damage is exponential, it's not linear." Or in other words, as the water level increases, the level of damage tends to rise much more steeply than the mere level of water itself.

Go read the rest.


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