Climate change didn’t come up in any of the three debates, though Candy Crowley did mention it in passing, if only to note that it wasn’t going to be discussed. In fact, it’s hardly been mentioned in the entire campaign, even though, as I wrote last week, it is one of the most important issues that will be decided by the outcome of the election. Green blogger Nathan Currier at Huffington Post has a grimly amusing take on the timing of Hurricane Sandy right at the climax of an election season that so desperately avoided talking about the climate. Here’s Currier:
In a time when climate silence trumps climate science, when the candidates seem terrified to mention the ‘C-word,’ Candy, I hope you enjoy meeting Sandy.
Currier’s main point is that man-made climate change is directly responsible for the storm. Climate scientists and writers seem to be of three schools of thought on the question. Everyone seems to agree that the magnitude of the storm results from the collision of three distinct weather events, the hurricane itself, a cold front moving down from the Arctic and an early winter storm coming from the Midwest. One school (for instance, this very cautious piece by New York Times Dot-Earth blogger Andrew Revkin) says that the unlikely coming together of the three weather events is made more likely by the documented warming of the planet and reflects the models put forward by mainstream climate science. (Recall that Hurricane Irene, one of the top 10 killer storms of the last 30 years, wandered up the coast just last year.) But, he says, you can’t categorically state direct causality. L.A. Times science writer Neela Banerjee talked to some scientists who are equally cautious.
A second school (like this piece by Science20.com contributor Robert Cooper) says that at least one or two of the three events is a direct reflection of climate change, and would have been highly unlikely in past decades before the greenhouse effect began to make itself felt. The third school argues, like Currier at HuffPost, that all three events can be directly attributed to the global warming process.
[A]ll major components of this superstorm show the signature of human-induced climate change to varying degrees, and without global warming the chance of the three occurring together like this would have a probability of about zero. So, let’s make it simple, and just say climate change caused this storm.
I’ll name the three events quickly and then explain them in greater detail.
Every observer that I’ve read, regardless of their views on climate change, agrees that the storm’s magnitude and northern reach result from a confluence of three distinct weather events. One is the unusual trajectory of this hurricane, coming late in the season and moving north and westward into the northeast coast rather than doing what most hurricanes do: either cruising due west over the Gulf of Mexico or drifting northeastward and heading out over the Atlantic. The second event is the cold front moving down from Canada, which is becoming a more frequent phenomenon of late and is a major factor behind the storm’s northwestward tilt. The third is the early winter storm moving east from the Great Lakes. The coincidence of the three running into each other is what created what’s been dubbed Frankenstorm.
The first factor, of course, is the most important. The warming of the oceans feeds the air currents with greater moisture and greater energy. There’s been quite a bit written in the last few years about the impact of warming oceans on increased storm activity in the Atlantic-Caribbean hurricane region. Average water temperatures have been moving upward, as Cooper shows with some good charts. This year the waters off New Jersey reached a record high, some 5 degrees above average.
The second, the unusual cold front, is a direct result of the melting of the Arctic ice cap. As I mentioned in my column last week, the disappearance of much of the Arctic ice cover exposes the dark ocean surface, absorbing the sun’s heat rather than reflecting it, which changes the flow of critical Northern Hemisphere air currents. I was referring to the Arctic jet stream, the cold current that normally circulates laterally in a west-to-east direction over the northern latitudes. In recent years it has been meandering southward in late summer and autumn because of the warm air rising from the Artic Ocean. It meets the northward-moving late-season hurricane and “blocks” the storm’s normal tendency to drift eastward over the Atlantic, driving it instead inland.
All this is magnified by the early winter storm moving east from the heartland. Currier and Cooper describe it pretty well. Currier thinks it too is influenced by climate change. Cooper doesn’t. Take your pick.
If the jargon is confusing, try this piece from ClimateCentral.org, which describes the various factors in fairly graphic terms—and doesn’t seem to consider the winter storm from the heartland as a separate event, but rather a byproduct of the hurricane.