VICTORIA has experienced a 40 per cent decrease in autumn rainfall since 1950 and climate change is a key factor, a report has found.
There were also seasonal rainfall declines in Western Australia's southwest and southern Queensland.
A reduction in the number of La Nina events and changes in weather systems from the Indian Ocean were also partly responsible for late rainfall across Victoria, the CSIRO's Wealth From Oceans Flagship study found.
During the past 58 years, a decrease in alternating high and low pressure systems over Victoria had led to rising sea level atmospheric pressure, report co-author Dr Wenju Cai said.
"This weakening is reinforced by a warming of the Indian Ocean which is, at least in part, due to global warming," he said.
"This suggests that a component of climate change is active in southern Victoria receiving less rainfall."