Research has shown human factors are likely to have influenced Australia's recent hot summer.
The University of Melbourne has released a study examining more than 90 climate model simulations of Australian summer temperatures over the past 100 years.
The research, published in the journal of the American Geophysical Union, shows the record-breaking summer occurred at a time of weak to neutral La Nina conditions.
Co-author, Professor David Karoly, says researchers are now more than 90 per cent sure of the link.
"The influence of increasing greenhouse gases, the influence of changes in climate due to human activity have been much more apparent as the cause of the angry summer, as it's been called, that we experienced last summer," he said.
"The extreme summer that we experienced was five time more likely than if we had just had natural factors influencing the climate."
© ABC 2013
17:37 EDT Much of western New South Wales has begun a heat wave, reaching at least five degrees above average for at least five days, averaging a maximum of 35 degrees or more.