Australia is "staring down the barrel” of a potentially extreme El Nino and positive Indian Ocean Dipole (IOD), yet this will not necessarily bring a repeat of the record bushfires that devastated the east coast a few years ago. 

All major modelling groups are projecting a return to at least moderate El Nino this summer. For Australia, this likely means a return to drought and bushfire. 

“The obvious question being, will it be like Black Summer all over again? The simple answer is probably not – unless something unexpected happens,” Risk Frontiers Climate Risk Scientist Stuart Browning said. 

The 2019-20 Black Summer bushfires were unusual because they were preceded by an extremely rare southern hemisphere Sudden Stratospheric Warming (SSW) in September 2019. 

Mr Browning says this was the rare “black swan” that forbode the devastation to come. 

“One major driver of the Black Summer fires was completely unexpected,” he said. “The SSW could be considered the “black swan” that amplified it from dangerous to catastrophic. 

“That predicated three years of climate turmoil, including some of the most disruptive and costly natural catastrophes in Australia’s history.” 

The Black Summer fire season was “extraordinary” and occurred due protracted drought and particular tropical climate drivers – and the very rare SSW phenomena, which while commonly observed in the northern hemisphere are almost unprecedented in the southern hemisphere. 

It has only ever been observed in 2002 – and 2019 when a sudden warming of the stratosphere in September altered the path of westerly winds over the Southern Ocean, resulting in increased frontal activity over southeast Australia.  

The chance of another SSW in the near future is small, Mr Browning says. 

He cites 2021 climate model simulations showing under a warmer climate, SSW should become less frequent, to only once every 300 years – and notes the world has just experienced its hottest days ever on July 3 and 4, with global average temperature exceeding 17 degrees Celsius for the first time.  

By spring 2019 the landscape was extremely dry and the climate drivers aligned for a dangerous bushfire season. Fronts in spring and summer are one of the key drivers of dangerous bushfire weather and dust storms, Mr Browning says, and are usually proceeded by hot dry north-westerly winds which desiccate the landscape meaning bushfires are easier to start and can quickly grow to become out of control.  

The 2019/2020 bushfire season was closely followed by three consecutive La Ninas which brought extreme flooding to Australia and record insurance bills exceeding $12 billion.  

“These (climate phenomena) relationships can provide some predictability for the coming season,” Mr Browning said, adding though that "one of the main complexities of the climate system is that nothing happens in isolation.”  

Earlier this month, the World Meteorological Organisation declared El Nino conditions had developed in the tropical Pacific for the first time in seven years.  

The El Nino Southern Oscillation (ENSO) and IOD positive typically bring drought and bushfire weather to Australia’s eastern states, while La Nina and IOD negative deliver flooding rains.