The study, conducted by the University of New South Wales (UNSW), indicates that the worst droughts all coincide with fluctuations in Indian Ocean temperature. Australia’s current post-1995 drought is the worst in 100 years.
The researchers say their findings, to be published in Geophysical Research Letters, explain why a series of La Niña weather events have failed to break the current drought. Such events usually bring Pacific rains to Australia.
Caroline Ummenhofer, who led the research, said: "We have shown that the state of the Indian Ocean is highly important for rainfall and droughts in south-east Australia, more than the variability associated with the El Niño/La Niña cycle in the Pacific Ocean. The Indian Ocean Dipole is the key factor for driving major south-east Australian droughts over the past 120 years." The IOD affects winds over the ocean and so determines whether southern Australia gets wet or dry conditions, she explained.
Traditionally, scientists have linked El Niño events in the Pacific – which leave drier weather in the western Pacific and Australia — with the country’s droughts. La Niña has the opposite effect, leaving the western Pacific warmer and increasing the chance of wet conditions over Australia.
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