Fire seasons are getting longer around the world – especially in Australia. A new study shows that, between 1979 and 2019, annual fire seasons have become an average of 14 days longer.
In Australia, the fire season has increased from 100 days per year to 130 days per year. There’s also been a 56% increase in extreme fire weather days.
The study is published in Reviews of Geophysics.
The researchers examined global weather records from the past 40 years to discern when, each year, different parts of the world were at risk from bushfires or forest fires. They also examined the land area burned by fires each year.
Interestingly, while fire seasons have increased in length, there’s been a decrease in the total area burned by wildfires at a global scale over the past 20 years. The area burned has decreased by roughly a quarter worldwide.
Read more: Australia’s future of fire
“That’s because over the last 40 years, we have continued to put in more and more money to fight fires,” explains co-author Dr Pep Canadell, a Chief Research Scienctist in CSIRO’s Oceans & Atmosphere division, and executive director of the Global Carbon Project.
“And, over the last 40 years, we have done a lot of deforestation, and converted a lot of grassland into cropping. So we have less forest to burn, less nature to burn in many parts of the world.”
The African savannah accounts for a huge amount of this decrease, which – until recent grazing and human management – saw fires every year.
The trend is also not true of Australia, where other research done by Canadell and colleagues shows a 350% increase in burned areas over the past 30 years.
“That’s the nature of going global – you just get the big patterns,” says Canadell.
“When it gets into details, you need to be careful.”
Read more: World is unprepared for 50% increase in global wildfires
The extension of the fire season is set to increase over coming decades, according to the researchers. If climate change is permitted to continue to 2°C of warming, boreal forests in Siberia, Canada and Alaska and temperate forests in the western US are all expected to face unprecedented fire weather, like that which contributed to the Black Summer bushfires in Australia of 2019-20.
At 3°C of warming, the researchers expect “virtually all world regions” to experience unprecedented fire weather.
“It’s an incredible frustration for many people, seeing the changes that are already happening,” says Canadell. “Not just what potentially may happen in the future, but the fact that a lot of things are happening now – and now we have high certainty that it has a very strong imprint of human-induced climate change.”