Australia should prepare for “megadroughts” that last more than 20 years and will worsen due to human-induced global heating, new research has found.
Megadroughts are exceptionally severe periods of below average rainfall that last decades. Climate modelling by the Australian National University, published in the journal of Hydrology and Earth System Sciences last week, found droughts spanning more than two decades have occurred in Australia over the past millennia and reoccur every 150 to 1,000 years, depending on the modelling used.
The study concluded that megadroughts of 20 years or more were “a natural feature of the Australian hydroclimate”, supporting previous research drawn from ice cores that found a 39-year drought hit eastern Australia about 800 years ago.
But Dr Georgy Falster, who led the research, said that a megadrought has not yet been officially recorded because Australia’s observational rainfall records have only been kept for a relatively short period of about 120 years.
“If they happen every 150 years we are due for one very soon,” Falster said. “Or we might not see one in our lifetimes.”
In the US south-west, extreme heat and declining moisture levels since 2000 have created a megadrought considered to be the driest period in 1,200 years.
Falster said the modelling highlights the need to prepare for future megadroughts that are likely be exacerbated by global heating.
“Forewarned is forearmed,” she said. “We now know that these megadroughts are a possibility which means we can be prepared for them.
“Even if the chance of a megadrought happening is lower … the potential consequences if we’re not prepared are so big that we need to prepare.”
She said Australia needed to implement robust water management plans, support measures for drought-prone rural communities and introduce environmental protection plans to mitigate the severe affects of a megadrought.
But ultimately, she said, reducing greenhouse gas emissions would be the only way to lessen the severity of future droughts.
Australia has had four major droughts since offical rainfall records began at the turn of the 20th century. The report’s modelling suggests these have not completely captured the possible range of rainfall variability in Australia, potentially causing an underestimation of drought risk in Australia’s water policy.
Falster said Australia’s last major drought, which set the conditions for the catastrophic 2019-20 black summer bushfires, was exacerbated by global heating.
The Australian government is developing a national climate change adaption plan and risk assessment. A spokesperson for the federal environment department said Australia “needs to be better prepared for and better manage increasing risks from climate change”.
The assistant minister for climate change, Jenny McAllister, said the government would “do everything we can to reduce our emissions”.
“However, we must also take steps to protect Australia’s economy, society and natural environment from the changes scientists tell are already locked in,” McAllister said.
