Are our bush fires getting worse?
Almost certainly yes. Identifying the underlying causes is no simple matter, but a new study of Antarctic ice cores may shed light on the matter, while also suggesting that we may be underestimating the intensity of future fires.
The study was a collaboration between multiple organisations, led by the ARC Centre of Excellence for Climate Extremes at the University of Tasmania. It acknowledges previous research showing fire intensity increases over a quarter to almost half of global burnable land masses, with decreasing relative humidity a driver of 75+% of increases, and rising temperatures for 40% of significant trends.
The new study, which focused specifically on South-East Australia, goes further. It concludes that the intensity of the 2019/20 Black Summer fire weather was unprecedented since observations began in 1950, while the frequency of above-average fire weather leading up to and including Black Summer has only occurred once since 1950 (early 1980s).
But it also notes that our observation records are inadequate for longer-term study, with our fire observations reliably extending only back to 1950, though proxy rainfall records (based on indirect data) can stretch back 500 years. To go further, the team found a new way to use existing data from ice cores to extend the historical record of extreme bushfire weather: sea-salt concentration.
“The sea-salt aerosol records captured in Antarctica go much further back than our weather records in Australia,” says the study’s lead author Dr Danielle Udy. “The ice core data shows that at least seven times over the last 2000 years, bushfire weather in south-east Australia was as bad as or worse than during the Black Summer bushfires of 2019/20. These new findings show natural climate variability can produce even more severe bushfire weather. On top of that, climate change is further adding to the intensity and frequency of severe bushfire weather.”
The report concludes that not only is climate change fuelling larger fires, but that the new evidence of natural variability extremes over the 2000-year reconstruction indicates that massive future fires could be caused by natural events exacerbated by human-induced climate change.
The report also highlights the influence of Westernised land management decisions since white occupation of Australia and the disruption of Indigenous cultural burning practices. Indigenous knowledge is still more robust on this.
“Planned burning meant that in most places there was simply not enough fuel for killer fires, and where there was, for example in dense forest with scrub, people ringed it with open country heavily grazed or frequently burnt,” writes ANU Emeritus Professor Bill Gammage In the First Knowledges publication Country: Future Fire, Future Farming. “Fire has always been part of being Australia,” he writes in a moving chapter called ‘Poor Fella My Country’, “but what that means has been upended since 1788. Then it meant maintaining an alliance; now it means fighting an enemy. Or, to judge from some responses to Black Summer, dodging an enemy.”