Human-caused climate change increased the chances of Australia experiencing extreme fire weather by at least 30% - and possibly much higher - finds new study.
The research was led by World Weather Attribution, an international initiative co-led and hosted in the Environmental Change Institute.
In 2019, unprecedented forest fires devastated southwest Australia, forcing many to evacuate or stay inside their homes for weeks, and leading to the loss of vast swaths of Canberra's national park and the deaths of millions of animals.
To understand whether these fires were affected by climate change, researchers from Australian, European and American universities carried out a rapid attribution study, comparing current conditions (with over 1°C of global warming) to the climate as it was around 1900.
The team found that human-caused climate change increased the chances of Australia experiencing extreme fire weather by at least 30%. But, given that the climate models are known to underestimate the observed trends in extreme heat, they concluded that the real increase could be much higher.
"The fire weather risk increased to a large extent because of more intense heat waves. High temperatures draw moisture out from the foliage on the forest floor, meaning it can burn more easily," explained Dr Friederike Otto, co-lead for WWA and acting director of the Environmental Change Institute.
"But current models underestimate heat extremes, which means they are likely underestimating the impact of climate change on fire weather risk. We need to continue to test our models in the real world to improve them so we can provide higher confidence risk information at the scales where people live and make decisions."
The study used observations and climate models, and focused on changes to the Fire Weather Index—a measure of weather conditions that describes the risk of bushfires. The researchers also examined extreme heat and meteorological drought (periods of very low rainfall), which are important elements of the Fire Weather Index.
A week of hot temperatures, like that experienced in southeast Australia during December 2019, was made at least twice as likely due to human influence on the climate, and heatwaves in Australia are now 1-2°C hotter. However, the researchers were not able to directly link the recent record low annual rainfall nor the driest month of the fire season with climate change.
"The experience of living in a city smothered in smoke for weeks on end was stressful and difficult," said Dr Sophie Lewis, a study author from the University of New South Wales and based in Canberra. "Climate change is now part of Australia's landscape, and contributed to the fires and extreme heat we lived through in southeastern Australia."
Global efforts aim to limit global warming to 1.5°C above pre-industrial levels. If global temperatures rise by 2°C, the study found that the fire weather conditions experienced in 2019/20 would be at least four times more common as a result of human-caused climate change.
The study received widespread media attention, including Nature, BBC, and Scientific American. Rapid climate change attribution was recently listed as one of Tech Review's breakthrough technologies 2020.