The Inconvenient Facts on Australian Bushfires

  • Date: 15/01/20
  • Roger Pielke Jr, Forbes

We live in a time where every extreme weather or climate-related event is immediately associated with human caused climate change. Such associations are often not really about the science of climate, but rather a symbol used to exhort in the political battle over climate change. 

inconvenient facts Australian bushfires
A dehydrated and injured Koala receives treatment at the Port Macquarie Koala Hospital in Port … [+]AFP VIA GETTY IMAGES

For instance, on one extreme there is Michael Mann, of Penn State University, who is spending an academic sabbatical in Sydney. He claims that “The brown skies I observed in the Blue Mountains this week are a product of human-caused climate change… it’s not complicated.” Mann frequently uses the climate issue as the basis for electoral politicking – he calls for Australians to remove their Prime Minister: Australians are going “to have to vote out climate change deniers like [Scott] Morrison.”

In contrast, the Australian Academy of Science says that the causes of bushfires are actually extremely complicated: “Bushfires, along with other weather and climate challenges, pose complex and wide-ranging problems. Population growth, climate change, temperature extremes, droughts, storms, wind and floods are intersecting in ways that are difficult to untangle and address.” And rather than calling for changing out individual politicians, the Academy calls for improved policies: “Everything, including urban planning; building standards; habitat restoration; biodiversity and species preservation; and land, water and wildlife management will need careful and measured consideration.”

The climate issue is so deeply politicized that some will cheerlead the politicization of the issue, some even going so far as to even deny any connection between climate change and fires at all. Nowadays, the politicization of scientific issues is often intense, but it is not uncommon. Climate change of course is an extreme example of science that is variously hyped and denied, making it difficult for non-experts to tell the difference. And using your political preferences to sort what you think is good science from bad is never a good idea.

Their summary is not likely to make anyone happy at the political extremes of the climate debate, but it is a fair representation of the current state of the science, as found in leading assessments and the peer-reviewed literature. I encourage you to read it in full, but below are some highlights.

First, and crucially, they conclude: “The impact of anthropogenic climate change on fire weather is emerging above natural variability.” Human-caused climate change affects “fire weather” which they define as “periods with a high likelihood of fire due to a combination of high temperatures, low humidity, low rainfall and often high winds.” 

However, the emergence of that impact has only been detected in ~22% of the world’s burnable land area, according to a recent studyby John Abatzoglou and colleagues. They conclude that, “Detection and attribution of global fire activity to anthropogenic climate change is confounded by influences of other anthropogenic activities such as land‐cover change, population, and fire suppression as well as temporally limited satellite‐based fire records.”

In 2011, we contributed an early paper proposing a methodology focused on quantifying the “timescale of emergence” of a signal of human-caused climate change on tropical cyclones (hurricanes) and their impacts. The idea behind this approach is to use climate models, assuming for purposes of analysis that their projections are accurate, and ask when would we expect to detect a signal of human-caused climate change in climate variables or in their impacts. 

It will always be easier to detect the role of human-caused climate change weather and climate data (like in fire weather) than it will be to detect that role in societal impacts (like in the number of buildings burned). As we explained in an analysis of Australian bushfire losses over time: “bushfire damage is not solely a function of bushfire weather; far from it, in fact. Even given a gradual aggravation of bushfire weather due to anthropogenic climate change or other factors, a bushfire still has to be ignited. Once ignited, a bushfire then has to traverse the landscape and impact a populated area, where outcomes in terms of damage will be a function of the spatial disposition of dwellings with respect to the fire front, and especially distance of properties from the bushland boundary.”

In the Abatzoglou study, the 22% of the burnable land area where detection of the role of human-caused climate change has been achieved includes the Amazon, Mediterranean, Scandinavia and Western North America. It does not include Siberia or Australia. 

That’s right, according to the latest research looking at the issue, the role of human-caused climate change in Australian bushfires has not yet been detected. It remains to be seen if the fires of 2019/2020 will alter that conclusion, but according to the Abatzoglou study, such detection is not expected until the 2040s. And that conclusion depends upon projections based on an extreme (and implausible) scenario for future emissions (RCP8.5), so detection may take a bit longer, assuming the projections are correct.

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