Aus to face stronger El Nino patterns

AUSTRALIA will face fiercer El Nino weather patterns - causing severe drought - as a result of human-induced global warming, world-first research led by Sydney scientists has shown.http://www.theland.com.au/news/agriculture/general/news/aus-to-face-stronger-el-nino-patterns/2678925.aspx

While the El Nino cycles typically trigger drought in the eastern states, so-called super El Ninos - such as those in 1982 and 1997 - have been detected since the mid-1970s.

These extraordinary events involve sea-surface temperatures warming in the west of the Pacific Basin and spreading eastwards, the reverse of more typical El Ninos.

In a study published in Nature, researchers led by authors from the University of NSW found the trigger for the unusual patterns was a weakening of westward-flowing currents along the Pacific equator.

Eastward-spreading El Ninos matter because the pool of heat over the western Pacific is likely to shift to the east during such events, taking rainfall with it and exacerbating drought conditions over Australia, said lead author Agus Santoso, a senior research associate at the university's Climate Change Research Centre.

As the world heats up, the eastern Pacific is expected to warm faster than the west. Since winds respond to pressure differences - with trade winds blowing east to west - the current flows are likely to weaken as conditions across the Pacific become more similar, Dr Santoso said.

Even with relatively modest levels of global warming in the future, the number of eastward-propagating El Ninos is expected to double.

The findings are likely to trigger further research to understand how much rainfall patterns are likely to change, he said.

The 1982 and 1997 events led to highly unusual weather events causing disruption in fisheries and agriculture costing tens of billions of dollars globally and leading to the deaths of tens of thousands of people, the university said in an accompanying statement.

During the 1982 event, US crop losses alone were estimated at as much as $26 billion in current dollars.

"While more frequent eastward-propagating El Ninos will be a symptom of a warming planet, further research is under way to determine the impact of such events in a climate that is going to be significantly warmer than today," co-author Dr Wenju Cai, a senior scientist at CSIRO, said.