Bushfires in Australia have burned millions of acres in Australia, killing 24 people and many more livestock and wild animals. In terms of area burned, the fires have exceeded the recent fire seasons in California and the Amazon Rainforest, combined. The severity of this year’s fire season prompts the question of how these fires may be related to climate change.
The Washington Post Editorial Board writes that the severity of the fires should be a climate warning for the whole world and an example to motivate greater greenhouse gas emission reductions from Australia and the United States. Offering a different perspective in the Wall Street Journal, James Morrow says that there is more at play than just climate change, and that the “climate-change narrative grossly oversimplifies bush fires, whose causes are as complex as their recurrence is predictable.” So which is it?
Scientists have known for some time that global warming would put Australia at greater risk from bushfire. While a wildfire always need some source of ignition (e.g. lightning or human activities), bushfires and wildfires are exacerbated during hot dry weather, which transforms vegetation into particularly effective fuel for fires. So all else being equal, temperature increases associated with global warming will increase fire hazard. And in the case of Australia, scientists have already attributed increasing temperatures averages and extremes in Australia to global climate change and one recent study has identified human-caused climate change as a leading factor in worsening fire risks in Australia (ht Ron Bailey at Reason).
Below is a graphical representation of Australian temperature and precipitation averages from the 20th and 21st century, put together by Robert Rhode using data from Australian Bureau of Meteorology. The red dots represent years from 2000-2019; they all fall on the warm side of the long term average. Meanwhile, 3 of the 4 wettest years since 1910 have occurred since 2000 and 10 of the 11 hottest years on record occurred between 2000-2019 as well. 2019 is much drier and warmer than any year on record (see this 2019 update from the Bureau of Meteorology).
Though many factors contribute to wildfires, the reason the Australian wildfires are so much worse this year than other recent years is the combination of record drought and record heat. #AustraliaFires
History of national-average temperature and precipitation since 1910. pic.twitter.com/aHh3kDFIZ7
— Robert Rohde (@RARohde) January 4, 2020
In an article for Scientific American, Australian climate scientist Nerilie Abraham explains how conditions this year became so hot and so dry. The long-term temperature increase driven by global warming is part of the story, but it appears to have been exacerbated by specific long-term weather patterns (ocean temperatures in the Indian Ocean and winds around Antarctica) to make this year particularly bad, with several dry winters for the past few years and then a hot, dry, and windy summer. Research groups will look back on these fires and estimate the relative effect of human-caused changes and natural variability that created the conditions for such large fires. Until their quantitative results are available, we are left with the simple storyline that a combination of human and natural factors favored fire prone conditions this year.
The Post is right that 2019 and its fire season offer a window to the future. As warming progresses, temperatures like those in 2019 will become more common. So while, Morrow is right that fires will continue to happen, it’s obviously true, similar conditions should be expected to arise. That means that land management to reduce fire risk and better emergency response could be all the more necessary as part of adapting to climate change.
But how much climate change we need to adapt to is a matter of emissions. If current trends in greenhouse gas emissions and climate change continue, leading to about 3C of global warming, the extreme heat witnessed last year in Australia will be pretty average later this century. As that happens, years with heat like 2019 will be more common. If emissions reductions proceed in line with climate goals, then years like this one could be more the exception than the rule.
This blog post was co-authored with Zach Zobel, a scientist with the Woods Hole Research Center.
Photo credit: Pexels