Megadroughts that last more than two decades and are more severe than anything in recent experience could soon hit Australia, according to fresh climate modelling.
The droughts are exceptionally severe, long-lasting and widespread and can last decades or even centuries, researchers at the Australian National University and ARC Centre of Excellence for Climate Extremes say.
The ANU-led team found 20th century droughts in south-western and eastern Australia were longer on average compared to those in pre-industrial times.
The research painted a picture of future droughts in Australia that were far worse than any from recent years.
The findings do not factor in human impact on the climate and the effects of climate change since the Industrial Revolution.
"The combination of climate change on top of naturally occurring megadroughts that could last for 20 years means that, in the future, Australia could see droughts that are worse than anything in recent history," modelling co-author Georgy Falster said.
Megadroughts were part of the natural variations in Australia's climate, but human-induced changes were probably making the prospect of such an extreme event more likely, he said.
"We must consider, and prepare for, the possibility that one of these multi-decade megadroughts could occur in the near future," Dr Falster said.
"We could see a megadrought occur every 150 years or 1000 years."
As part of the modelling, researchers looked at the full range of droughts Australian could experience, while investigating how climate change was altering their characteristics.
They used multiple climate models to simulate previous droughts and predict how they might change in the future.
ANU professor Nerilie Abram, a co-author of the research, said parts of Australia already experiencing longer droughts because of climate change - including the Murray-Darling Basin - could expect future rainfall declines.
"It is likely that changes to drought intensity could still arise as climate change continues to worsen," she said.
"One example of this is the 21st-century 'Tinderbox Drought', which was only three years long but was exceptionally intense and set the conditions for the Black Summer bushfires."
