Ancient shellfish remains rewrite 10,000-year history of El Nino cycles The planets largest and most powerful driver of climate changes from one year to the next, the El Niño Southern Oscillation in the tropical Pacific Ocean, was widely thought to have been weaker in ancient times because of a different configuration of the Earths orbit. But scientists analyzing 25-foot piles of ancient shells have found that the El Niños 10,000 years ago were as strong and frequent as the ones we experience today. The results, from the University of Washington and University of Montpellier, question how well computer models can reproduce historical El Niño cycles, or predict how they could change under future climates. The paper is now online and will appear in an upcoming issue of Science. We thought we understood what influences the El Niño mode of climate variation, and weve been able to show that we actually dont understand it very well, said Julian Sachs, a UW professor of oceanography. The ancient shellfish feasts also upend a widely held interpretation of past climate. Our data contradicts the hypothesis that El Niño activity was very reduced 10,000 years ago, and then slowly increased since then, said first author Matthieu Carré, who did the research as a UW postdoctoral researcher and now holds a faculty position at the University of Montpellier in France. Climate models and a variety of datasets had concluded that El Niños were essentially nonexistent, did not occur, before 6,000 to 8,000 years ago, Sachs said. Our results very clearly show that this is not the case, and suggest that current understanding of the El Niño system is incomplete. sciencecodex/ancient_shellfish_remains_rewrite_10000year_history_of_el_nino_cycles-139252
Posted on: Sat, 09 Aug 2014 17:39:16 +0000
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