Climate change to cause twice as many severe floods in Australia and Pacific
Australia and its region will probably be hit by almost twice as many severe floods this century like the ones that devastated southeast Queensland four years ago, according to new research.
An international team of scientists led by Wenju Cai, of the CSIRO, wanted to find out whether global climate change would affect the frequency of catastrophic flooding caused by extreme episodes of the La Nina weather pattern.
They found that extreme La Nina phases would occur every 13 years as the planet warmed against a past frequency of only one every 23 years.
They published their results in the British journal Nature Climate Change today.
La Nina brings floods to Australia, New Guinea, the western Pacific Islands and vast areas of Southeast Asia and China, and droughts to the USA’s southwest.
It is part of the El Nino/La Nina cycle, also known as the El Nino Southern Oscillation, or ENSO.
ENSO is a natural mode of climate variability caused by changes to atmospheric circulation triggered by a gradient in sea surface temperatures across the Pacific.
La Nina occurs when the central to eastern equatorial Pacific is colder than normal, Dr Cai said. “It inhibits the formation of rain clouds there but enhances atmospheric convection and rainfall in the western Pacific,” he said.
The scientists probed the future with 21 global climate models skilful at simulating extreme La Nina periods in the historical record. The work formed part of the big international science program, the Coupled Model Intercomparison Project phase 5.
The team compared the frequency of severe La Nina episodes between 1900 and 1999 with model projections for the frequency in the greenhouse world between 2000 and 2099.
The overall frequency of La Nina phases would remain at the current level of about one in every two to seven years over the rest of this century but the rate of extreme episodes would rise dramatically, Dr Cai said.
That was partly due to changes in atmospheric circulation because land masses including New Guinea, Indonesia, the Philippines, Singapore and Malaysia would warm more rapidly than the central Pacific waters, he said.
Another mechanism was steeper vertical ocean temperature gradients as the climate changed. And a rise in the number of extreme El Niño phases would also have an impact. El Niño, the reverse of La Nina, brings drought to our region.
“Extreme El Niño events are conducive to the development of extreme La Nina events,” Dr Cai said.
“Most extreme La Nina events occur in the year after an extreme El Niño, meaning more devastating weather events and more frequent swings between extremes from one year to the next, with profound socio-economic consequences,” he said.
SOURCE: THE AUSTRALIAN/PACNEWS
An international team of scientists led by Wenju Cai, of the CSIRO, wanted to find out whether global climate change would affect the frequency of catastrophic flooding caused by extreme episodes of the La Nina weather pattern.
They found that extreme La Nina phases would occur every 13 years as the planet warmed against a past frequency of only one every 23 years.
They published their results in the British journal Nature Climate Change today.
La Nina brings floods to Australia, New Guinea, the western Pacific Islands and vast areas of Southeast Asia and China, and droughts to the USA’s southwest.
It is part of the El Nino/La Nina cycle, also known as the El Nino Southern Oscillation, or ENSO.
ENSO is a natural mode of climate variability caused by changes to atmospheric circulation triggered by a gradient in sea surface temperatures across the Pacific.
La Nina occurs when the central to eastern equatorial Pacific is colder than normal, Dr Cai said. “It inhibits the formation of rain clouds there but enhances atmospheric convection and rainfall in the western Pacific,” he said.
The team compared the frequency of severe La Nina episodes between 1900 and 1999 with model projections for the frequency in the greenhouse world between 2000 and 2099.
The overall frequency of La Nina phases would remain at the current level of about one in every two to seven years over the rest of this century but the rate of extreme episodes would rise dramatically, Dr Cai said.
That was partly due to changes in atmospheric circulation because land masses including New Guinea, Indonesia, the Philippines, Singapore and Malaysia would warm more rapidly than the central Pacific waters, he said.
Another mechanism was steeper vertical ocean temperature gradients as the climate changed. And a rise in the number of extreme El Niño phases would also have an impact. El Niño, the reverse of La Nina, brings drought to our region.
“Extreme El Niño events are conducive to the development of extreme La Nina events,” Dr Cai said.
“Most extreme La Nina events occur in the year after an extreme El Niño, meaning more devastating weather events and more frequent swings between extremes from one year to the next, with profound socio-economic consequences,” he said.
SOURCE: THE AUSTRALIAN/PACNEWS
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