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    Global climate change

    New Hypothesis may explain Short-Term Reduction in Global Warming Rate

    10/18/2013, 10:51:54 AM

    Future short-term variability in global temperatures may be more predictable than previously thought, according to a new research hypothesis from Georgia Tech.

    The decrease in the global warming rate over the past 10-15 years, which was not well predicted by climate models may be more of a product of what Georgia Tech scientists call 'stadium waves'.


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    Key excerpts from the Georgia Tech News Center story......

    The paper’s authors, Marcia Wyatt and Judith Curry, point to the so-called ‘stadium-wave’ signal that propagates like the cheer at sporting events whereby sections of sports fans seated in a stadium stand and sit as a ‘wave’ propagates through the audience. In like manner, the ‘stadium wave’ climate signal propagates across the Northern Hemisphere through a network of ocean, ice, and atmospheric circulation regimes that self-organize into a collective tempo.

    Wyatt and Curry identified two key ingredients to the propagation and maintenance of this stadium wave signal: the Atlantic Multidecadal Oscillation (AMO) and sea ice extent in the Eurasian Arctic shelf seas. The AMO sets the signal’s tempo, while the sea ice bridges communication between ocean and atmosphere. The oscillatory nature of the signal can be thought of in terms of ‘braking,’ in which positive and negative feedbacks interact to support reversals of the circulation regimes. As a result, climate regimes — multiple-decade intervals of warming or cooling — evolve in a spatially and temporally ordered manner. While not strictly periodic in occurrence, their repetition is regular — the order of quasi-oscillatory events remains consistent. Wyatt’s thesis found that the stadium wave signal has existed for at least 300 years.

    The stadium wave periodically enhances or dampens the trend of long-term rising temperatures, which may explain the recent hiatus in rising global surface temperatures.

    The new hypothesis also indicates how long the reduction in the warming rate might last.....

    “The stadium wave signal predicts that the current pause in global warming could extend into the 2030s," said Marcia Wyatt, an independent scientist after having earned her Ph.D. from the University of Colorado in 2012.

    Sea ice impacts

    The study also provides an explanation for seemingly incongruous climate trends, such as how sea ice can continue to decline during this period of stalled warming, and when the sea ice decline might reverse. After temperatures peaked in the late 1990s, hemispheric surface temperatures began to decrease, while the high latitudes of the North Atlantic Ocean continued to warm and Arctic sea ice extent continued to decline. According to the ‘stadium wave’ hypothesis, these trends mark a transition period whereby the future decades will see the North Atlantic Ocean begin to cool and sea ice in the Eurasian Arctic region begin to rebound.

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    You can read much more about this hypothesis right here.

    Link to the actual study right here.

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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    Global climate change