Experts warn extreme bushfire weather risk growing


“Many intense fires in south-east Australia are associated with strong winds channelled ahead of powerful cold fronts, with the winds drawn from the hot continental interior,” Professor Howden said.

“It’s like the air is being forced through a narrow pipe. Furthermore, if it is an intense and deep cold front, there may be strong, gusty winds after the front has passed, which also enhance fire spread.

“The frequency of these frontal systems is projected to increase by up to a factor of four by the end of this century due to climate change.”

Professor Howden said the weather conditions experienced on Tuesday could be repeated on Saturday.

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In 2009, a joint CSIRO and Bushfire CRC study, Assessing the Impact of Climate Change on Extreme Fire Weather Events over South-Eastern Australia, warned these weather events were increasing in frequency and could occur up to four times more often by 2100 if carbon emissions and climate change were unchecked.

The study said a southerly change could bring “gusty, post-frontal winds that can greatly enhance fire spread”.

“The wind-shift associated with these fronts can cause the flank of a fire to become a much longer head-fire, and this effect is exacerbated,” it said.

Last week, the Bureau of Meteorology reported a major climactic factor contributing to eastern Australia’s severe drought was beginning to break down, but it was too early to say if or when the big dry would end. The positive Indian Ocean Dipole – when sea-surface temperatures are warmer in the western Indian Ocean and cooler in the east – has dropped over the past three months, edging closer to conditions that make decent rain more likely in eastern Australia. 

Another drought influencer, the El Niño-Southern Oscillation (ENSO), remains in neutral mode.

But Professor Howden said there was no guarantee the big dry was over.

“The Indian Ocean Dipole is breaking down, but it’s still high and coming from very high levels. And neutral ENSO conditions don’t mean it will be wet, that means anything can happen with dry or wet conditions,” he said.

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