Streetwise Professor

January 11, 2010

Blame the MPH

Filed under: Climate Change — The Professor @ 8:37 pm

Finally coming out of the pretty intense cold that had temps in Houston down into the low-20s.  I am perfectly willing to stipulate that one cold month doesn’t say too much about the correctness of the AGW hypothesis–and I would hope (probably in vain) that those flogging that hypothesis would do the same.

The NYT felt sufficiently concerned that some out there might conclude that the cold weather refuted AGW, so it ran a piece to explain that it did no such thing:

What’s going on? Global cooling?

Nope. A mass of high pressure is sitting over Greenland like a rock in a river, deflecting the cold air of the jet stream farther to the south than usual.

This situation is caused by Arctic oscillation, in which opposing atmospheric pressure patterns at the top of the planet occasionally shift back and forth, affecting weather across much of the Northern Hemisphere.

What’s notable this year is that the pattern of high pressure over the Arctic is more pronounced than at any time since 1950.

. . . .

No one is quite sure what drives these flip-flops in air pressure.

“I tend to think of it as a random thing,” said John M. Wallace, who is a professor of atmospheric sciences at the University of Washington. “I don’t think we understand any reasons why it goes one way one year and the other way another year.”

What does seem clear is that these oscillations have nothing to do with global warming, or, for that matter, global cooling. For one, they’re not new. And this winter’s cold has not been global. Santa, by North Pole standards, has been experiencing a balmy winter.

Well, according to one climatologist, and AGW skeptic, the late Marcel Leroux, (a) this certainly doesn’t have anything to do with AGW, because it doesn’t exist, and (b) the phenomenon of varying intensity and frequency of polar high pressure events actually explains variations in temperature (temporally and spatially) far better than the AGW hypothesis.  Thus, if Leroux is correct, the current cold weather could actually provide evidence against CO2 driven climate change.

Leroux set out his ideas in a book: Global Warming: Myth or Reality: The Erring Ways of Climatology.  He focused on just the kind of phenomenon described in the NYT piece, what he dubbed “Mobile Polar Highs” (MPH).  Interestingly, these MPHs cause exactly the effect described in the NYT article: cold temperatures at medium latitudes, and warm temperature at the pole experiencing winter.  A summary of the idea can be found here.

Leroux argued that the intensity of MPHs oscillates between rapid and slow modes on a decadal scale, and that this oscillation can explain (autocorrelated) variations in temperatures, as well as glaciation and deglaciation, fluctuations in sea ice and sea level, and other climate-related phenomena.

The book doesn’t provide a very extensive or convincing explanation as to what causes the shift between rapid and slow modes, but it is provocative, and does raise some serious empirical issues that the CO2-driven models don’t handle well.  It certainly provides considerable evidence of cyclical behavior of that would necessarily complicate any effort to isolate any CO2-driven temperature trend, especially in a relatively short time series of data.

The next several years could provide some evidence relating to Leroux’s hypothesis.  He argues that the MPH cycle has been in slow mode since the late-1970s.  If the current winter is the harbinger of a return to the rapid mode, the next several winters will be cold as well.

Moral of the story: the cold weather currently being experienced in much of the northern hemisphere could indeed be germane to the debate over AGW.

Note that Leroux was not an employee of ExxonMobil.  He was, in fact, a climatologist at the Jean Moulin University in France, and the director of the Laboratoire de Climatologie, Risques, et Environment at the University.  A real climatologist, in other words, and one who lived in the world of data, rather than the world of models.

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  1. I have played around with daily temperature data dating from the 1950s. There is a definite correlated warming trend in US cities since the 1970s. I am wondering if the AGW scientists found correlated warming in both northern and southern hemispheres. Has Leroux studied southern hemisphere MPH as well?

    Comment by Surya — January 12, 2010 @ 1:08 am

  2. It’s always AGW when it is getting warmer, but some random trend when it is getting cooler. Amazing coincidence.

    Comment by Howard Roark — January 13, 2010 @ 5:08 am

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