An atmospheric phenomenon in the Indian Ocean could increase under climate change tripling droughts and bushfires across the globe.
CLIMATE CHANGE IS LIKELY to almost triple the frequency of bushfires, floods and drought in Australia from one event every 17 years to one every 6 years, according to a paper published today in Nature.
The Indian Ocean Dipole is an atmospheric phenomenon that affects Australia's climate as well as those of other countries on the Indian Ocean and is a significant contributing factor to rainfall variability. Its positive phase usually results in droughts in the eastern Indian Ocean and floods in the western Indian Ocean.
The findings mean not just a rise in the number of droughts and fires in Australia and neighbouring countries in Asia, but also a rise in extreme weather events around the world, including Africa.
This is the first study of the extreme positive Indian Ocean Dipole's response to climate change, completed using an ensemble of climate models using the highest scenario of greenhouse gas emissions — equivalent to a 4.9°C temperature rise by the end of the century.
Dr Wenju Cai from CSIRO Marine and Atmospheric Research, who led the research, said it's very important to understand how an extreme positive Indian Ocean Dipole event may respond to climate change because of its global impact.
"Most of our severe bushfires were preconditioned by the Indian Ocean Dipole... When a summer season is preceded by an [extreme positive] Indian Ocean Dipole our bushfires tend to be much more severe," he said.
"Now this is in Australia, but it has global impact. [For example] in Indonesia, a positive Indian Ocean Dipole tends to cause drought. You may recall in 1997 we had a wild bushfire in Indonesia... emitting a lot of pollutants and smoke that caused health problems to many millions of people in the region and also cost lost economic activity because people couldn't go out because of the visibility problem.
"In the meantime, in eastern African countries, they experienced devastating floods, causing thousands to die... and displacement of many hundreds of thousands."
Professor Charitha Pattiaratchi studies climate change coastal effects and ocean currents at the Oceans Institute in the University of Western Australia. He didn't take part in the research but said although it focuses on one 'state' of the Indian Ocean Dipole, the paper is an important step towards understanding extreme positive Indian Ocean Dipole events.
He said one of the big challenges in climate science is predicting the behaviour of different ocean oscillations under high greenhouse gas scenarios, including El Nino Southern Oscillation (ENSO), North Atlantic Oscillation and Indian Ocean Dipole. "How [an extreme positive Indian Ocean Dipole] couples with the different ENSO phases still needs to be examined."
Dr Cai said the research, which was funded by the Australian Climate Change Science Program and the Goyder Institute in South Australia, has also raised a deeper line of inquiry around the Indian Ocean Dipole. "Our research discovered big things in how the Indian Ocean Dipole will respond to climate change but we are now looking more into regional scales, how the impact may be intensified under global warming. If you look locally, sometimes the impact is non-linear... So we are looking at that kind of non-linear prospect of the impact."
Yesterday the CSIRO announced that more than 30 jobs will be cut from their Marine and Atmospheric Research division, including eight in their Aspendale laboratory where Dr Cai is based.
