Monday, December 27, 2010

Regional Cold Extremes and Global Warming


December 22, 2010
Climate Science

There continue to be claims that the extreme cold weather in western Europe, in southeast Australia, and elsewhere are not inconsistent with a more-or-less monotonic annual globally averaged warming. However, these reports continue to miss the point that it is the regional anomalies that matter far more in terms of effects on society and the environment.

Recent reports that seek to rationalize the recent extreme cold events include:

Biting winters driven by global warming: scientists by Marlowe Hood [h/t to Marc Morano];

How a freak diversion of the jet stream is paralysing the globe with freezing conditions by Niall Firth

This article has also the erroneous statement:

“Experts are still unsure why this is but suspect it may be related to the EL Nino weather system as well as changes in sea temperatures and solar activity”

However, we are currently not in an El Niño pattern but a strong La Niña!

and:

That snow outside is what global warming looks like by George Monboit

In this latter news article, Mr. Monbiot writes:

“So why wasn’t this predicted by climate scientists? Actually it was, and we missed it. Obsessed by possible changes to ocean circulation (the Gulf Stream grinding to a halt), we overlooked the effects on atmospheric circulation. A link between summer sea ice in the Arctic and winter temperatures in the northern hemisphere was first proposed in 1914. Close mapping of the relationship dates back to 1990, and has been strengthened by detailed modelling since 2006. “

This failure to skillfully predict any of the extreme weather patterns we have seen in the past should be a wake-up call to policymakers and the public that the climate science community is overselling the prediction skill that is possible.

Unfortunately, they also continue to miss the significance that it is the regional circulations that matter much more, not a global average anomaly, as I discussed on my post:

An Example of Why Regional Weather Patterns Are More Important Than A Global-Average Temperature Anomaly

They seem to feel that the global average temperature anomaly and long term trend is the primary determinate of the weather we experience. However, it is not a useful metric for this purpose.

Moreover, until and unless they can skillfully predict observationally documented CHANGES in the statistics (probabilities) of the different major circulation patterns, their explanations are necessarily flawed. There is no evidence that the global climate model multi-decadal predictions (and even shorter term runs on a year or less into the future) have the needed skill.

This does not mean that added CO2, and other human climate forcings [that we discuss in our EOS paper, as well as natural focrings and feedbacks, are not important, but just that we can not predict their effects on circulation features.

Even for Europe we discussed the importance of regional wind circulations in our paper:

Otterman, J., R. Atlas, S.-H. Chou, J.C. Jusem, R.A. Pielke Sr., T.N. Chase, J. Rogers, G.L. Russell, S.D. Schubert, Y.C. Sud, and J. Terry, 2002: Are stronger North-Atlantic southwesterlies the forcing to the late winter warming in Europe? Int. J. Climatol., 22, 743-750.

Among our findings we wrote:

“We envisage that changes in the circulation over the European continent are forced by changes in the surface winds over the North Atlantic……. These large-scale circulation patterns are in a large measure influenced by the North Atlantic oscillation.”

The current extreme cold weather in western Europe certainly fits with this conclusion.
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