Understanding Climate Risk

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Posts Tagged ‘Nature Science Reports

Global warming breaks link between SAM and ENSO

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Global warming has caused SAM and ENSO to divorce according to Guojian Wang and Wenju Cai, published in Nature Science Reports on June 20. This is having major impacts on Australia and has contributed to the warm and dry conditions over the southern part of the continent since the late 1960s.

SAM is the Southern Annular Mode surrounding Antarctica, a band of wind and water that distributes hot, high pressure and cold, low pressure lobes around the Southern Ocean. This transfers atmospheric mass (pressure) between the mid and high latitudes. The positive phase is highly correlated with a positive phase of ENSO (the El Niño-Southern Oscillation), La Niña. A positive phase of SAM forces westerlies further south in autumn-winter, but in summer allows the easterly trades greater access, bringing in more moisture from the tropics and enhancing La Niña summer rainfall.

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