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by Larry

December, 2014

Our Unhinged Polar Jet Stream

Once rare, extreme weather events are becoming common. Formerly 100-year level floods, droughts, heat waves, and Arctic winter anomalies are now occurring every few years in the temperate zones. Insurance companies and governments having to provide more regular and expensive emergency relief have taken note. Our premiums and taxes will have to go up to cover the new reality.

10,000-20,000 years ago, climatic circumstances began to alter in ways far more favorable to human civilization than before. If recent patterns are indicative, that "happy time" may be coming to an end.

Since the year 2000, the U.S., Russia, Japan, China, and Europe have endured historically unprecedented frequency and severity of weather phenomena. A 2010 heat wave in Russia led to the deaths of over 55,000 people. Drought in the U.S. in 2012 was the most harsh since the 1930s, and, despite some recent rains and flooding, it remains largely intact. CA high pressure systems, even in winter months, have created the driest period for that state on record. Meanwhile, the Great Lakes region has experienced unusually hard winters, England and Wales have had their wettest winters since the 1700s, Atlanta, normally more pleasant in the frosty months, has suffered through devastating snow and ice storms, OK in 2011 had the hottest year ever for any U.S. state, two weeks of massive winter flooding in China forced half a million out of their homes, the Arctic has had bizarre heat waves, and Norway, typically snowed in during the coldest season, has had multiple January wildfires. Are these and many other instances of recently weird weather just random developments, or are they part of a pattern?

With meteorological science, it is hard to know for sure without many years of data and careful analyses. Nonetheless, a hypothesis has been presented which appears to fit the phenomena we are seeing. Its implications, if the theory is borne out, are worrisome. Whether or not one is a believer in humankind's activities being behind global warming, evidence is already clear that polar regions are heating up at a fast rate. Year to year shifts will still occur, but the long-term trend shows lessening of polar ice and less difference in temperatures between the arctic and temperate climate zones. The normal discrepancy between northern and temperate latitude temperatures has sustained a relatively constant wave of high speed upper atmosphere winds, known as the polar jet stream, mostly within a reasonably narrow band that included the U.S.' "Lower 48."

As that temperature difference between the two regions diminishes, it may be affecting the polar jet stream, causing its waves to become much steeper and slower. The jet stream waves now more often reach up toward the polar and down toward the tropical climate zones. As they get steeper, these waves also slow down or even stop their normal westerly to easterly northern hemisphere movements. The net result for residents of temperate climate zones, according to the hypothesis, can be additional and longer periods of intense weather.

As indicated, more analysis is required to determine if the recent changes in polar jet stream configurations are becoming a new normal, perhaps in response to significant alterations in the relative polar vs. mid-latitude temperatures, or if they will later prove to have been anomalous. Since the temperature shifts, however, are confirmed and increasing, it is reasonable to expect that the climate system will shift in some fashion to compensate. A slowing of the west to east jet stream movement coupled with the stream's having heightened amplitude would be logical changes accommodating this circumstance.

Were recent jet stream adjustments and their apparently related weather phenomena to become the new normal, we can expect more droughts and hotter temperatures in central and western U.S. and Canada, more cold waves in eastern North America, droughts in Europe and central Asia, plus severely wet weather in western Asia. Not merely insurance rates but food costs would increase substantially as agriculture will be more risky and less efficient with wilder weather.

A variety of factors seem to be correlated. Together they could make for a big shift in climate as a whole as well as for human interests:

  1. Polar temperatures are rising steeply, two or three times as fast as in the temperate lower latitudes;

  2. Icecaps and sea ice are thinning and shrinking, with almost a 50% reduction since 1900, and the trend, though showing significant variation over any few years' time, may be accelerating as darker areas reflect less solar radiation and absorb additional heat;

  3. The formerly sharp difference in temperatures between regions north of the polar jet stream and ones to its south has become more mild.

  4. Since that earlier sharp difference drove the polar jet stream's rapid westerly to easterly movement and held it in a relatively stable temperate latitude band, the lower temperature differential allows the jet stream to slow down and wander more. Think of how a creek in flood flows vs. when it has become an old and slow river. A map of the latter will show much more twisting and meandering along its course.

  5. Every now and then a less powerfully driven system will entirely stop in place, bringing prolonged periods of severe weather.

  6. Compared with previous weather norms, a slowed, more amplified polar jet stream will bring abnormally hot and dry conditions to some areas and abnormally cold and wet ones to others.

  7. Humans rely on fairly stable supplies of water and food, yet both will be less available as the polar jet stream moves less rapidly west to east and has a greater tendency to flow more steeply north or south than heretofore.

  8. Utility costs will also accelerate as greater extremes of cold and heat become common.

It is the job of politicians to reflect the views and needs of competing constituencies. Similarly, it is the job of private industry to protect its interests. It is hardly surprising that petrochemical or coal industries, for instance, do all they can to avoid taking into account potential adverse effects of their activities upon the environment or the climate.

We have big brains, though, and the possibility of using them. A few generations are but a blip in geological or evolutionary time. Yet in so short a span we are seeing the greatest die-off of other species in millions of years and transformations in the chemistry of our atmosphere and oceans that rival any that naturally would occur for many hundreds of thousands. Perhaps we might consider the implications for our descendants, even if we do not accept any responsibility ourselves for what is happening, if we do nothing to hold back the currently rapid pace of adverse change.

Maybe there are yet things we could do to help assure that our "happy time" continues for awhile longer. If not, there soon might be no turning back.

Just suppose the hypothesized relationships are accurate, as they may be. Then, if there is even a 10% chance that the polar jet stream is in the process of a mammoth shift to a new state that portends ill both for our kind and for the biosphere as we know it, would it not behoove us to respond if we can? Were our astronomers to discover a giant asteroid apparently on its way to our part of space, but said they were not yet sure it would strike Earth, though there seemed at least a 10% chance it might, would we not find the means to deal with such a threat and not wait till certainty arrived moments before the impact?

Still, there is reason for optimism. In both the historical period and in our kind's prehistory we have come close to the end of our particular branch and twig of the tree of life, yet have persisted, if only barely so, and gone on to thrive. With so much shared intelligence, it is scarcely credible that we shall now be as foolish as to ignore the many signs that, if ever, the time for creative, positive solutions is at hand.

Primary sources:

Evidence Linking Arctic Amplification To Extreme Weather In Mid-Latitudes. Jennifer A. Francis and Stephen J. Vavrus in Marine Rutgers Edu; March 17, 2012;

The Jet Stream Is Getting Weird. Jeff Masters in Scientific American; December, 2014, pp. 68-75;

There's Growing Evidence That Global Warming Is Driving Crazy Winters. Chris Mooney in The Washington Post; November 20, 2014.

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