VOA常速英语:Flooding in Australia Result of La Nina

Deadly floods in Australia and Brazil have proved devastating for both countries in recent weeks. And while Brazil's floods are being seen as a normal weather event, climatologists have determined a reason for the ones in Australia:  a regular weather phenomenon called "la Nina".  But there's a debate over whether global warming is playing a part in their intensity.

In Brazil, torrential rains take more than 600 lives.  Fourteen thousand are homeless.  The rain continues as do warnings of more deadly mudslides.

In Australia, weeks of flood waters in the northeast are receding and help is on the way. 

"Thursday morning, I woke up and I just couldnt go on and then everyone arrived," said a woman.

Now - what could end up as the worst flooding in 100 years - has moved further south.

Greg Holland is a climatologist with the U.S. National Center for Atmospheric Research. We found him attending to his vineyard in Australia, where he's in danger of losing his grapes because of mildew. He described  the floods to us via Skype.

"Literally walls of water five or 10 miles [8-16 km] wide and maybe 10 to15 feet [3-5 meters]- high, coming ripping down through places and you just have no chance when that type of water hits you,"  said Holland. "People are starting to call it an inland tsunami."

Climatologists blame the Australian flooding on a weather system called "la Nina". La Nina is a natural, cyclical event that cools the waters of the Eastern Pacific ocean and warms them in the west, near Australia.  The cycle lasts until the weather system called "el Nino" takes over and does the opposite.
Holland says global warming does play a part in the extreme rainfall.
"The intensity of it and the amount of rainfall has most definitely been contributed to by global warming," he said.
But, that's not what others say.  Rupa Kumar Kolli is the World Meteorological expert on El Nino and La Nina.  He also spoke with us on Skype.

"We do not have adequate evidence to suggest that global warming can lead to an increase or decrease in terms of intensity or frequence of el Nino or la Nina situations," he said.

Tony Barnston is the lead forecaster at Columbia University's International Research Institute for Climate and Society.  He says even if ocean temperatures warm overall, it's the range of difference between the eastern pacific and western pacific that brings on the systems.  He does not expect any global warming effects for many years.

"Changes are slower in the oceans, are much slower in terms of global warming than they are in the air over continents," said Barnston.

As for Brazil, Barnston agrees with other climatologists who say Brazil's flooding is not related to la Nina.

"It’s more of a random, smaller scale regional event," he said.

Barnston says that's because southeastern Brazil is prone to below-normal rainfall during a typical la Nina -  just the opposite of what's happening. 

Whatever the reason, climatologists expect the effects of this la Nina to continue for months, possibly even years.  Not good news to those affected.