2015-03-12. Warming Arctic may be causing heat waves elsewhere in world.

posted Mar 14, 2015, 8:16 AM by Alan Gould

By Carolyn Gramling, Science. For GSS Climate Change chapter 8. Excerpt: Global warming is increasing temperatures twice as fast in the Arctic as elsewhere on the planet. Some scientists have suggested that this so-called Arctic amplification can alter circulation patterns that affect weather in the United States, Europe, and Asia, potentially helping cause the powerful winter storms and deep freezes that have blasted the midlatitudes over the past decade. A new study suggests Arctic warming could ultimately pack a summertime punch, too, possibly contributing to extreme events such as the deadly 2010 Russian heat wave. Melting sea ice in the Arctic has left vast expanses of dark open water available to absorb the sun’s energy. In the late autumn and early winter, when sea ice is at a minimum and temperatures begin to cool, the ocean releases that extra heat and moisture back into the atmosphere. Those fluxes help drive a positive feedback effect, further intensifying warming in the region. One result of this Arctic amplification is that there’s less of a temperature difference between the Arctic and the lower latitudes. Some scientists have suggested that the lower temperature gradient is weakening the winds that circle the globe, particularly the polar jet stream. In the wintertime, the idea goes, a weaker, wavier jet stream could promote more and longer bouts of frigid air reaching farther south, leading to extreme snowfalls such as those that struck the eastern United States in the past few years. ...The jet stream is weaker in summertime, too—and it “has been weakening over the last 36 years....  http://news.sciencemag.org/climate/2015/03/warming-arctic-may-be-causing-heat-waves-elsewhere-world.

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