(Current Polar Jet Stream Configuration. Note the powerful Rossby-Wave zonal flow associated with the 9 month old Pacific Blocking Pattern continuing to flood the Arctic with warmer air and disrupting/collapsing the seasonal polar vortex while shoving Arctic air south over Canada and the US. Image source: University of Washington.)
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A massive rash of human-warming induced extreme weather sweeps across the US and, not surprisingly, the mainstream media has gotten its climate change messaging somewhat wrong again..
In a rather admirable attempt to show how human caused warming is creating and influencing the recent spate of extreme weather, numerous articles have all implicated the, now much renowned, polar vortex in a massive, 20-year, cold snap gripping much of the nation.
Over and over, media reports are the same: Polar Vortex Grips Nation!
Two Sides to The Polar Vortex Story: Human Warming and A Disrupted Arctic Cyclone
In all honesty, it’s hard not to chuckle at how the media has gotten the story somewhat wrong. A polar vortex is, in essence, a semi-permanent storm or cyclone that forms in the high Arctic during winter months. The existence of a polar vortex in the high Arctic is a normal condition. And the meteorological features it creates tend to trap colder air in its swiftly circling winds. Such a condition results in very cold temperatures in the far north, while warmer conditions tend to prevail much further south. The net result is keeping Arctic cold locked in the Arctic where it belongs as, usually, the storm centers in the Arctic Ocean near the North Pole.
But this winter, as in recent winters, something a bit out of the ordinary happened. The polar vortex shifted southward as it unraveled, causing the current US cold snap. And since these powerful Arctic cyclones pack quite a punch the related effects have been extraordinary and extreme — powerful winter storms, school and business closings due to the cold, and freak freezing episodes all over the US.
All that said, the anomalous movements and impacts of the polar vortex during 2014 are only half of the story. The other half involves how human-caused warming is directly influencing the vortex, altering its course and intensity, pushing it far beyond the limits of its typical Arctic confines.
Increasing Arctic heat resulting from loss of sea ice, worldwide ocean warming, and amplifying feedbacks to human warming have opened the door to more and more warm air invasions into the high Arctic. During winter time, the net effect of these warm air invasions is to disrupt the polar vortex, resulting in its more frequent weakening and collapse all while periodically shoving its storm center south.
In the current diversion and collapse, the polar vortex was severely disrupted while being shoved into the lower latitudes crossing Canada and the Continental US. The result was a rash of extremes not seen in the US in at least 20 years.
An Evolving Scientific Awareness of Human Warming’s Devastating Impacts
As early as 2001, scientific studies had found evidence for a correlation between weakening of the polar vortex and periodic cold conditions in the temperate latitudes (see NASA study here). Meanwhile, further studies (see links below) in recent years established a link between declining Arctic sea ice and Jet Stream configurations that brought on polar vortex weakening and collapse.
(Normal Jet Stream Pattern A vs disrupted Rossby-type pattern C. During winter, C is often the result of warmer air disrupting, weakening and/or collapsing the polar vortex. Image source: Commons.)
When the polar vortex weakens or collapses, warm air is drawn into its core. This causes an unwinding of the storm system and a displacement of its cold air and energy further south. The storm, as it unwinds, flings a powerful cold front to the south, driving bone-chilling Arctic air into some temperate regions even as the High Arctic takes on an unusual degree of heat (for the Arctic during winter time).
Current heat anomaly maps clearly display this condition:
(Image source: NOAA)
Note the prevailing, much warmer than average conditions over much of the Arctic, with cooler than average conditions over the US due to collapse and anomalous movement of the polar vortex. This was the very severe winter storm and extreme weather producing pattern that we warned of earlier in December.
Disruptions of the polar vortex have been predicted by climate scientists such as Dr. Jennifer Francis, Dr. James Hansen, and Dr. Jeff Masters, among others, who have warned of more extreme weather caused by, among other things, loss of polar sea ice. Dr. Hansen, in particular, has warned of very intense storms as Arctic melt continues to ramp up and more of the Arctic’s cold is pushed episodically southward where it will inevitably confront the warming temperate and tropical zones. In the end, Hansen warns of frontal systems packing the strength of hurricanes large enough to span entire continents. These are the powerful effects of continued Arctic warming and of which the current polar vortex collapse is but a symptom.
Let us all hope we are not unwise enough to push the climate system far enough to generate the kinds of storms Hansen fears. To that dark and not so distant future, what we are seeing now is merely prelude.