Dec. 28, 1:10 p.m. | Updated
Here was the scene out our back door here in the highlands of the Hudson River Valley early Monday morning:
Countless similar scenes have been recorded early in the Northern Hemisphere winter across western Europe and big swathes of the United States.
So it wasn’t surprising to read the takeaway line in an op-ed article over the weekend by Judah Cohen, a commercial weather analyst, on the seeming paradox of unusually wintry winters in many populous parts of the Northern Hemisphere even as the world warms:
It’s all a snow job by nature. The reality is, we’re freezing not in spite of climate change but because of it. [Read the rest.]
[Dec. 28, 1:08 p.m. | Updated I’ve posted an expanded exploration of Cohen’s winter-weather analysis.]
Cohen focuses on a hypothesis that he’s been assessing for quite a few years — a relationship between retreating sea ice, expanding Siberian snows and more widespread cold outbreaks. [In a comment below, Cohen elaborates on his work, noting that he has made predictions that support his analysis.]
Below I’ve rounded up a few reactions to Cohen’s thesis by other climate scientists similarly focused on winter weather, Arctic conditions and climate change.
There are quite a few video clips out there aiming to distinguish weather from climate, but the best — to my mind — is the one that follows:
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Its humor bites in a ways that could grate on both fans and foes of action on greenhouse gases. But it slips in just the right bits of basic information amid the chuckles. I e-mailed the link to Randy Olson, the
filmmaker and author of “Don’t Be Such a Scientist,” for a review. He’s a big fan of action on climate, but approved of this clip, as well:
It’s perfect. It’s totally confusing to the average person, and simply serves the purpose to put the issue of climate in front of them. I’m sure if I watched it twice more I’d get all the specific details, but I have a fairly disconnected viewing mind, so all that comes across to me is the idea of the government forcing you to learn climate science or go to prison, which is entertainingly silly, and innocuous.
Here’s the roundup of reactions to Cohen’s piece, “Bundle Up, It’s Global Warming” (I’m posting the e-mail messages in raw form so excuse a few acronyms, etc.):
Kevin Trenberth, a National Center for Atmospheric Research scientist who has long concluded that global warming driven by accumulating greenhouse gases is substantially influencing weather patterns:
I am aware of some German work that suggests the cold outbreak pattern might somehow be stimulated by reduced Arctic Sea Ice. I have not seen the study but count me skeptical.
The cold and snow in Europe was “balanced” by very warm temperatures in Greenland: classical negative NAO [North Atlantic Oscillation]: perhaps.
The was a large so-called blocking high in North Atlantic that led to the polar outbreaks into Europe and so that is where the cold air went, making it warmer in behind. Now that is more a weather or meteorological description, not a statement of cause.
Coincidentally pressures have been much above normal in the far North Pacific, and that is typical with La Nina. The pressures were high enough to make the main branch of westerlies active to the south and led to the pineapple express and heavy rains in California. It is quite a strong La Nina, and that is a forcing of the atmosphere by the anomalous atmospheric heating patterns linked to SSTs [sea surface temperatures].
Now is it a coincidence to have such strong wave structure affecting both N Pacific and Atlantic at same time? In other words, a scientific question is what role did the La Nina play, especially if one mixes it up with a negative phase of the NAM/NAO? (NAM = Northern Annular Mode which is a much preferred term to “Arctic Oscillation”).
The atmosphere is global and I don’t really believe in coincidences. But problem not solved. Most likely a large element of natural variability. Count this commentary as thinking out loud.
David Robinson, chairman, geography department, Rutgers University, and the New Jersey state climatologist:
I share Kevin’s wait and see attitude regarding evidence for all of the “links” Judah was suggesting in his piece. Sometimes the anomalous, the rare event, occurs. For instance, should New Jersey have a 10″ plus snow event over the next 24 hours it will be the first one in the past 10 La Nina winters going back to 1970. I haven’t looked further back with a full set of observations, but the Philly/Mt. Holly National Weather Service office stated the other day that Philly has only had one such event over the past century of La Ninas (in 12/1909).
On a grander scale, I’ve heard talk of an open Hudson Bay this fall influencing [atmospheric] wave patterns across the North Atlantic into Europe. Can’t recall the source…but something else to toss into the “mix.”
As for influences of an “open” Arctic Ocean on fall and winter snow cover, there are several studies underway. I’m involved with one with colleagues at Hunter College, U. Colorado and Columbia. Clara Deser at NCAR is also cooperating with the team and looking at it on her own too. We have a recent paper out that begins to address this:
Ghatak, D., A. Frei, G. Gong, J. Stroeve & D. Robinson (2010). On the emergence of an Arctic amplification signal in terrestrial Arctic snow extent. Journal of Geophysical Research – Atmospheres 115, D24105, doi:10.1029/2010JD014007. A study in progress. As is Judah’s work, which goes back about 10 years.
As for his assertions regarding colder winters of late… I can’t speak for temperatures, I’ll leave that for others, but snow cover extent hasn’t exactly gone through the roof. Yes, Northern Hemisphere, Eurasia and N. America have had their share of above average extents in fall and winter (//climate.rutgers.edu/snowcover) (check out monthly and seasonal graphs), but not an inordinate number. However there is something to be said for fall increases in Siberian extent (check out the monthly departure maps for October and November..under “Visible Satellite Charts”). Wish we had better (and enough) info on snow depth/water equivalent from Siberia, clearly more is needed.
And then there is the issue of decreasing spring snow extent, but that’s a discussion for another time…
Anthony Broccoli, director of the Center for Environmental Prediction, Rutgers University:
Judah has been publishing on the link between Eurasian snow cover in autumn and the NAM/NAO in the following winter for quite some time. I’m open minded but not persuaded by any putative connection to climate change, however. An unusual winter in 2009-10 does not make a trend, even in light of similar conditions this month. I’m also not clear about the statement that seven of the previous nine winters were unusually snowy and cold across the Eastern United States and Eurasia. I don’t see that signal, at least in December-January-February temperature, in the NCDC “dot maps”…
The bottom line? There are surely relationships between winter conditions in different regions around northern latitudes. A delay in the spread of winter sea ice in the Arctic is generally going to produce more snow, just as late-season open water on the Great Lakes results in astounding depths of white stuff in places like Syracuse, N.Y.
But it’s still the case that weather, even brutal winter weather, is (yet again) not climate.
It’s a daunting task to try to detect any links between short-term fluctuations in extreme weather events and the rising influence of accumulating greenhouse gases on climate, given that extreme weather is, by definition, rare.
As John Michael Wallace of the University of Washington put it in an e-mail: “Secular trends in rare, imprecisely defined events like big east coast snowstorms are very difficult to pin down.”
That means this will be an arena generating plenty of research, but also scientific disagreement, for a long time to come.
What’s important, to my mind, is not to confuse this kind of normal, healthy scientific debate with more basic understanding of human contributions to, and responses to, climate change.
[Here’s some related coverage in Forbes, the Christian Science Monitor and on Tom Yulsman’s CEJournal blog.]