Europe Hammered by Winter, Is North America Next?   
       
   Feb 16, 2012: For the first half of this year's winter, the big news was warm   
   temperatures and lack of snow. Ski resorts were covered in bare dirt, while   
   January temperatures in southern California topped July highs.   
       
   Then, out of the blue, Europe got clobbered: Over the past two weeks,   
   temperatures in Eastern Europe have nose-dived to -30 degrees Celsius (-22   
   degrees Fahrenheit). Blizzards and the bone-chilling cold have resulted in the   
   deaths of over 550 people so far, with rooftop-high snow drifts trapping tens   
   of thousands of villagers in their homes and cutting off access to entire   
   towns. It has even snowed as far south as North Africa.   
   [...]   
   This map shows temperature anomalies for Europe and western Russia from   
   January 25 to February 1, 2012, compared to temperatures for the same dates   
   from 2001 to 2011. The anomalies are based on land surface temperatures   
   observed by the MODIS instrument on NASA's Terra satellite. [more]   
   NASA climatologist Bill Patzert of the Jet Propulsion Laboratory explains what   
   happened: "A couple of weeks ago, Mother Nature did an about face. The tight   
   polar vortex that had bottled up the cold arctic air in the beginning of   
   winter suddenly weakened. Cold air swept out of Siberia and invaded Europe and   
   the Far East."   
       
   The "tight polar vortex" is caused by the Arctic Oscillation (AO), a   
   see-sawing pressure difference between the Arctic and lower latitudes. When   
   the pressure difference is high, a whirlpool of air forms around the North   
   Pole. That's what happened earlier this winter: the whirlpool was more   
   forceful, corralling the cold air and keeping it nearer the pole.   
   [...]   
   An artist's concept of the Arctic Oscillation in its negative phase. [more]   
   [video] Now the vortex is weakening. With "the AO Index going negative," as an   
   expert or weather-nerd might put it, cold air escapes from that whirlpool and   
   heads southward, resulting in the killing extremes now plaguing the other half   
   of the planet.   
       
   However, even the breakdown of the vortex cannot completely account for the   
   severity of the winter Europe is suddenly experiencing. As strange as it   
   sounds, some climatologists, among them Judah Cohen of Atmospheric and   
   Environmental Research in Massachusetts, attribute the unusual cold to global   
   warming. Cohen contends that since sea ice is being melted by warmer   
   temperatures in the Arctic, more moisture is available for the atmosphere to   
   pick up - and drop as snow. As a result, Siberian snow cover has increased,   
   and this snow cover has a cooling effect which reaches East Asia and Europe.   
       
   "Cohen's research is cutting edge and could bring important improvements to   
   forecasting climate and weather over North America and Europe," says Patzert.   
   "Cohen and others are on the threshold of understanding of how climate change   
   affects the behavior of the Arctic Oscillation1."   
       
   Patzert adds, however, that this winter is just one of many severe winters   
   that have changed European history. "Looking back, Mother Nature has taken us   
   on some very wild rides."   
       
   He cites the winter of 1683/84, when the Thames River in England stayed frozen   
   with a thick layer of ice for nearly two months, as an example.   
       
       
   If only Napolean had a weather satellite.... [more] "And let's not forget the   
   frigid winter of 1812, when Napoleon's Grande Armee was decimated by the   
   extreme cold in Western Russia."   
       
   Patzert notes that European history would have been much different if Napoleon   
   had had a good meteorologist on his staff and some NASA satellites to warn him   
   about what he was marching into.   
       
   "And the turning point of World War II occurred in 1941, when Germany's forces   
   were nearly frozen in place," he adds.   
       
   There are many other examples2, and climate change can't be blamed for all of   
   them.   
       
   "There's always going to be some natural variability. Every episode of high   
   temperatures or extreme cold isn't climate change. Sometimes it's just   
   weather!"   
       
   The weakening Arctic Oscillation could soon bring a return of winter to North   
   America as well, although Patzert doesn't expect it to be as severe as what's   
   happening on the other side of the Atlantic.   
       
   Is there any relief in sight for Europe?   
       
   "The good news is that this crippling cold snap arrived mid-winter. With the   
   vernal equinox less than six weeks away, this AO episode will become muted -   
   hopefully."   
       
   Hang on till Spring."   
       
       
   Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   What Happened to all the Snow? -- Science@NASA ScienceCast video   
       
   The Arctic Oscillation and Arctic Weather Patterns -- from the National Snow   
   and Ice Data Center   
       
   Footnotes:   
       
   1To stress the complexity of the system, Tom Wagner, the Earth Science   
   Division's Cryosphere Program Manager at NASA headquarters, notes "a new paper   
   out by Chang in the Journal of Climate that talks about impact of the Indian   
   Ocean on North America: The warming of the Indian ocean from global warming in   
   turn causes warming of central US. There more to the story than diminished ice   
   cover. We're dealing with a complex, interconnected system, and warming has   
   unusual affects with teleconnections." Complicating matters further, there are   
   also larger cycles superimposed, but that's another story.     
       
   2More examples of extreme winters:   
       
   In 1310, a 20-year trend of cold weather was actually to blame for the Great   
   Famine that began in 1315. And it probably had a lot to do with poor nutrition   
   that made people more susceptible to the Black Death that struck in 1348.   
       
   1816 was the "Year Without a Summer" in the Northern Hemisphere. On July 4th   
   that year in Savannah, Georgia, the high temperature was 46øF! There were food   
   shortages due to crop failures and livestock deaths in the US, Canada, and   
   Western Europe.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.75   
    * Origin: NCS BBS (1:3828/7)