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This item was posted on December 27, 2010, and it was categorized as Climate Change, meteorology.
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Winter does too

People made their way through Times Square on Sunday evening as the Northeastern blizzard pushed into New York. (Photo courtesy of asterix611 via Flickr Creative Commons)

Global warming causes an increased chance of snowstorms like the one that has been pummeling the Northeast?

That was the red meat thrown out by the New York Times today Christmas Day in an Op Ed column by Judah Cohen, director of seasonal forecasting for Atmospheric and Environmental Research. Not surprisingly, the climate contrarians are gnashing and feasting.

Cohen’s theory is actually pretty interesting. But I have no idea whether he’s right — and his theory is not the point of my post today. (If you’re interested in what other climate scientists have to say about it, check out Andy Revkin’s post today at DotEarth.)

Update 12/27/10: Deja vu all over again? Last February, there was snow in all 50 states, and frigid conditions extended all the way down to the Gulf Coast. I wrote about it in this article, and I mentioned that the Arctic Oscillation was in a particularly intense negative phase. When that happens, the Arctic tends to be warmer and lower latitudes tend to be colder than normal. Sounds familiar, doesn’t it? And guess what’s happening with the Arctic Oscillation right now? It has been in a persistent negative phase since November — and it reached quite a low level just eight days ago.

So, what is the overall point of this post? The graphic at the bottom makes it quite nicely. But first . . .

Consider Prins Christian Sund near the southern tip of Greenland, where it’s currently 34 degrees and sunny. That’s almost warm enough to go swimming!

Well, maybe not. But my guess is that the residents of Prins Christian Sund are considerably happier today than are most New Yorkers, who are enduring an epic blizzard.

And by the way, if you are a New Yorker and you’re not looking forward to the lakes of slush that will no doubt be collecting at every street corner by Wednesday, you might consider a quick get away to the southern tip of Greenland. Wednesday’s high there is forecast to top out at 40 degrees.

As I said in the headline: weather happens. And when it does, it often becomes the trigger for yet another skirmish in the climate change wars. Maybe the snowstorm was influenced by global warming. Maybe it wasn’t. That’s certainly a scientific question worth exploring.

But as always, what’s most important is the long-term trend — which is defined on a decadal time scale, not a daily, monthly or even yearly one. And on a decadal time scale the picture is quite clear: the decade that is about to draw to a close has been the warmest on record. Moreover, since 1970, each decade has gotten steadily warmer, as this graphic from NASA’s Goddard Institute for Space Studies shows:

This graphic, from a paper by James Hansen and colleagues at NASA’s Goddard Institute for Space Studies shows how the temperature of the sea and land surface departed from the 1951 to 1980 average during each decade, starting with the 1970s.

I realize that this is yet another chunk of red meat for some readers. So before you gnash and feast, please read my earlier post on how GISS and other groups determine long-term temperature trends. After you’ve had a look at that, come back here and have at it.

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This thing has 2 Comments

  1. Mauri Pelto
    Posted December 28, 2010 at 4:15 am | Permalink

    Cohen’s idea is not new about the role of Siberian Snowcover, that dates back at least 30 years, however, the his implementation of it in a forecast model is. He has taken a long standing concept and included it in a long term forecast model that has been performing well. Look back to work by Gong et al (2003) and a second Gong et al (2003) Cohen is co-author on both.

  2. Steve Bloom
    Posted December 28, 2010 at 7:17 pm | Permalink

    Cause and effect, i.e. attribution, of this stuff is tricky. A solid tele-connection like thgis can do the job for a forecast, but it doesn’t mean that the one causes the other. Causation for the increased snowfall seems straightforward, but as Trenberth says the tropics are generally the place to look for a driver for a major shift in atmospheric circulation. These are interesting times for climate theory.

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  1. Posted December 27, 2010 at 6:46 pm | Permalink

    [...] [Here's some related coverage in Forbes, the Christian Science Monitor and on Tom Yulsman's CEJournal blog.] [...]

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