Mar 4, 2020 - Energy & Environment

How climate change helped drive Australia's fires

Residents defend a property from a bushfire at Hillsville near Taree, 350km north of Sydney on November 12, 2019.

Residents defend a property from a bushfire at Hillsville near Taree, some 200 miles north of Sydney on Nov. 12, 2019. Photo: Peter Parks/AFP via Getty Images

Human-caused climate change helped fuel the weather conditions of Australia's unprecedented bushfires, an international team of climate scientists at the World Weather Attribution group found.

Why it matters: The conditions increased the chances of Australia experiencing extreme fire danger by at least 30%, an estimate researchers told a news briefing was conservative. This is the first time scientists have been able to quantify how climate change has affected the risk of fires, they said.

Driving the news: The Australian summer that ended Feb. 29 was the second-hottest on record, after the previous one, per the Australian Bureau of Meteorology (BOM). The prolonged drought continues in some parts of the country.

  • "Overall, 2019 was the hottest and driest year here in Australia, and that's since high-quality records commenced in 1910," said study co-author Dr. Sophie Lewis, from the University of New South Wales, Canberra during the briefing.
  • "In spring, 95% of Australia had forest fire danger index values in the highest 10% ever recorded. In many jurisdictions across Australia, the bushfire season commenced months early in spring ... in some places, it began in winter."

What they did: The researchers combined observed trends with climate models as they examined the Fire Weather Index, a measure of conditions including heat and drought describing bushfire risk, in the worst-hit areas of southeast Australia.

  • They compared current conditions, with over 1°C (33.8 °F) of global warming, to the climate as it was around 1900.

What they found: A week of hot temperatures, like those experienced in Australia's record heat wave last December, was found to be at least twice as likely to be caused by human influence on the climate. The recent heat waves are hotter by 1-2°C than they were around 1900, the study authors note.

  • If global temperatures rise by 2°C (35.6°F), the weather conditions behind the fires would be at least four times more common as a result of human-caused climate change. Current international plans for emission reductions would still lead to warming that substantially exceeds this level.

The big picture: At least 48 million acres of land burned in the blazes, killing 34 people and more than 1.5 billion native animals, the study notes. In New South Wales, the fires raged for 240 days — since early July last year through this Monday, per the NSW Rural Fire Service. In Victoria, the final major fire — which burned almost 400 square miles of land — was finally contained Friday.

  • The bushfires destroyed nearly 6,000 buildings — including "many thousands of homes," Lewis said.

Zoom in: Lewis directly experienced the bushfires' effects, as "thick, hazardous smoke" enveloped Canberra in the extreme heat.

  • "In January, the national park that forms a large part of our home exploded in flames," Lewis recalled. It was extinguished last week after razing an estimated 83% of native vegetation.
  • "This was an event that had an enormous ecological and human cost, and it's really because of this that it's so important to understand ... the contributing factors," she added.

Zoom out: The findings aren't unique to Australia. Professor Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute said, "We found pretty much the same thing in Europe for both the Mediterranean heat wave of 2017 and last year's heat wave in Western Europe."

  • Maarten van Aalst, of the Red Cross Red Crescent Climate Centre in the Netherlands, said an increased risk was observed in other places impacted by fire, including California.

What's next: The report will appear in the Natural Hazards and Earth Systems Science open review journal this month.

Go deeper: Australia fires: "Widespread devastation across the ecosystem"

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