Monday, May 31, 2010

Climate change will make El Nino worse

Matt Cawood in Stock & Land (Australia): The severity of the El Nino-Southern Oscillation (ENSO) cycle can be expected to increase as the planet warms - but greater warmth will also boost other weather phenomena that may check that severity. That’s the nil-all finding of a review looking at how ENSO, one of the planet’s most important climate cycles, could develop under climate change.

The international science review, which involved scientists from CSIRO and the Bureau of Meterology and was recently published in Nature Geoscience, found that future ENSO cycles would be governed by countervailing influences. On one hand, warming could change ocean currents and winds in ways that could deliver El Nino conditions to eastern Australia far more often than in the past. But on the other hand, increased cloud formation could dampen tropical warming and shift the climatic balance in other directions.

Dr Wenju Cai of CSIRO’s Wealth from Oceans Flagship said that greater humidity is one phenomena certain to occur if the tropics continue to warm.

…In the tropics, observations from the past 50 years and modelling of a warmer future over the next century suggest that the winds most affected will be the east-to-west tropical trade winds. The trade winds push warmer waters to the western Pacific, off the coast of Australia and New Guinea. If the winds quieten, Dr Cai said, those warm waters are likely to disperse back to the east.

That’s not encouraging for Australia. Warm Pacific waters generate upwelling convection currents that suck in moist ocean air. When those warm waters are in the Pacific’s west, they drive what eastern Australian agriculture recognises as wet La Nina years….

Nothing says El Nino like a dismasted ship in a rough sea, by Bonaventura Peeters, from the mid-17th century

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