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La Nina could ease Australian drought

Australia’s drought-hit farmlands may see vital summer rains from a La Nina system that could develop next year, bringing relief after a year of sweltering temperatures above the global average, scientists said on Wednesday.

Australia’s Bureau of Meteorology said farms in the wheat belt of southern Queensland and northern New South Wales states had a 60 per cent chance of above-average summer rain, while farms in southern Western Australia state had a 70 per cent possibility.

“The signs are very early to be saying that we will have a La Nina next year, but there are some positive signs,” said Andrew Watkins, senior climatologist at the bureau’s National Climate Centre.

Watkins said the early signs of a La Nina, which normally brings wet weather to the western Pacific, forming were the fact that subsurface water in the Pacific was starting to cool down surface water and that trade winds were relatively strong.

“A neutral to a La Nina is most likely given current conditions,” Watkins told reporters during a briefing on the World Meteorological Organization’s (WMO) report on global climate in 2008 released in Geneva Dec. 16.

This year, the world’s average temperature was 14.3C (57.7F), the 10th warmest year on record. But Australia saw temperatures above the global average to record its 15th warmest year on record.

The WMO said a slight slowdown in warming in 2008 was due to a moderate to strong La Nina in the Pacific in late 2007.

La Nina brings cooler temperatures and rain to the western Pacific as a result of cooler ocean water. An El Nino, on the other hand, is brought about when the heating of the western Pacific leads to drier weather and is the main factor behind the worst drought in a decade in Australia.

Watkins said the late 2007 La Nina was warmer than most La Nina years and warmer, drier conditions fuelled mid-latitude droughts across the globe, in Australia, California, Argentina and Africa.

Australian rainfall in 2008 was below average, particularly during the main cropping and pasture season from April to October.

“These conditions exacerbated severe water shortages in (Australia’s) agriculturally important Murray-Darling Basin, resulting in widespread crop failures in the area,” said the WMO report.

Australia’s 2008-09 wheat crop is forecast at 19.969 million tonnes, well down from earlier forecasts, due to a lack of rain in South Australia and parts of the eastern states of New South Wales and Victoria, said a government earlier this month.

But Australia’s overall winter crop, including barley and canola, was forecast to be about 31 million tonnes, a 36 per cent increase from 2007-08, due to above-average spring rainfall.

The bureau said Australian farmers could look forward to good rainfall during the rest of the Southern Hemisphere summer, December-February, but again warmer temperatures.

“Parts of southeast Queensland and northern NSW, which are summer cropping regions, have about a 60 per cent chance of getting above the medium rainfall, which is of course a good sign for them,” said Watkins.

“Through southwest WA there is a higher likelihood, about a 70 per cent chance of getting above-average rainfall. The rest of Australia will be drier,” he said.

“There are some good signs at the moment going into next year for Australian rainfall – as to whether that will end the drought is another thing because we need many years of rainfall to catch up in our dams.”

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