February 10, 2011

Australia Likely To Suffer More Weather Extremes

New research reveals that weather-battered northern Australia could be in for more extreme weather events.

Researchers studied coral cores that reveal a centuries-old climate record for the region, according to a recent Reuters report

Corals can help scientists go back in time by revealing years that were unusually wet or dry.  The annual changes or variations in weather are recorded in growth rings that can be studied by drilling and extracting long cores.

"The corals are providing another piece of evidence that maybe suggests that we are seeing some consequences already of global warming," Janice Lough, a senior scientist at the Australian Institute of Marine Science in Queensland state, told Reuters from Townsville on Thursday.

Lough examined 17 corals cores taken from reefs off Queensland's northeast coast.  The rings in the cores data shows a 300-year climate record from the 17th century until when they were collected in 1981.

Northern Queensland typically gets most of its rain during the summer monsoon season and is at the mercy of the El Nino and La Nina weather patterns, which normally bring drought or floods.

The current strong La Nina is blamed for record floods that have inundated large areas of Queensland in recent months, killing dozens of people, crippling coal mines, swamping thousands of homes and damaging crops.

She said her study found that the frequency of weather extremes seems to increase in recent centuries.

"It can be difficult to detect whether any changes are happening just because of that high natural variability," she said, but added that the long-term record suggested some sort of change had occurred. "That tropical rainfall variability will become more extreme."

She said the cores come from Porites coral domes that can grow up to 26-feet high and be centuries old, growing between 1 and 1.5 cms a year.

In her research, Lough looked into slices of the coral under ultraviolet light to study the growth bands.

During wet years, rivers flush a lot of plant matter and a mix of compounds called humic acids into the ocean and these acids are absorbed by the coral and stored in its skeleton.  Growth bands with more humic acid show up more brightly than bands from drier years.

Lough said coral records were another piece of the climate jigsaw, given the lack of long-term historical weather data, particularly in the Southern Hemisphere and the tropics.

"Corals are natural history books," she added, revealing growth rates, changes through time and the amount of freshwater run-off from land.


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