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Australian Floods Linked to Climate Change?

January 12, 2011

Scientists stated on Wednesday that global climate changes are a likely trigger of the recent intense monsoon rains that have resulted in the deadly flooding of the Australian state of Queensland.

The Queensland floods have killed 16 people since the downpours started in December, inundating towns, crippling the coal mining industry, and now swamping the state’s main city of Brisbane.

One of the strongest La Nina patterns ever recorded is being blamed for the rain.  La Nina is a cooling of ocean temperatures in the east and central Pacific, which usually leads to more rain over much of Australia, Indonesia and other parts of Southeast Asia.

La Nina weather patterns lead to stronger easterly winds in the tropics that pile up warm water in the western Pacific and around Australia. The Pacific Ocean has historically switched between La Nina phases and El Ninos, which have the opposite impact by triggering droughts in Australia and Southeast Asia.

Indonesian officials said on Wednesday that they expect prolonged rains until June. 

David Jones, head of climate monitoring and prediction at the Australia Bureau of Meteorology in Melbourne states, “The first thing we can say with La Nina and El Nino is it is now happening in a hotter world,” he told Reuters, adding “that meant more evaporation from land and oceans, more moisture in the atmosphere and stronger weather patterns.”

“So the El Nino droughts would be expected to be exacerbated and also La Nina floods because rainfall would be exacerbated,” he said, though adding “it would be some years before any climate change impact on both phenomena might become clear.”

“It’s a natural phenomena. We have no strong reason at the moment for saying this La Nina is any stronger than it would be even without humans,” said Neville Nicholls of Monash University in Melbourne and president of the Australian Meteorological and Oceanographic Society.

But he told Reuters reporter David Fogarty that global atmospheric warming of about 0.75C over the past half century had to be having some impact. “It has to be affecting the climate, regionally and globally. It has to be affecting things like La Nina. But can you find a credible argument which says it’s made it worse? I can’t at the moment.”

“The extra water vapor fuels the monsoon and thus alters the winds and the monsoon itself and so this likely increases the rainfall further,” claims prominent U.S. climate scientist Kevin Trenberth, “so it is easy to argue that 1 degree Celsius sea surface temperature anomalies gives 10 to 15 percent increase in rainfall,” he added.

Some scientists said it was still too soon to draw a definite climate change link to the floods.

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