Australia’s frightening bushfires, which kicked off an early fire season in September 2019, have already had cataclysmic effects, and the continent is still just in the early months of the southern hemisphere’s summer. The New South Wales Rural Fire Service has described the bushfires as unprecedented in size and scale, having burned more than 46 million acres (18.6 million hectares), killed at least 29 people, and destroyed more than 2,200 homes.*
Parts of Australia have had the worst air quality in the world. The air quality in Sydney has literally been alarming, having set off smoke alarms in buildings throughout the city’s central business district and exceeded hazardous levels for more than 30 days. Military assets have been deployed in response to the fires at a scale not seen since World War II. Researchers estimate that more than a billion animals have been killed. Several species will likely be pushed to extinction.
The conditions and climate change-wildfire connections in Australia have been strikingly similar to those amplifying California’s record 2018 wildfire season, but on a much larger scale. Scientific unknowns remain regarding some of those connections, but others are a straightforward result of physics – more heat creates more wildfire fuel.
The politics and climate policy environment down under, on the other hand, more closely bring to mind those at the national level in the U.S. than to the situation in California.
How Climate Change Exacerbated Australian and Californian Fires Despite widespread conspiracy theories about the bushfires, emerging science continues to find links between global warming and worsening wildfires, with the issue a focus of continuing investigation. As climate scientist Kevin Trenberth explained in a recent interview with videographer Peter Sinclair, global warming directly intensifies wildfires by drying out soil and vegetation, creating more fuel to burn farther and faster. That’s particularly a problem in drought-prone regions like Australia and California.
The Millennium drought in southeastern Australia from 1997 to 2009 was the driest 13-year period on record, according to a report by Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). The drought was broken by Australia’s two wettest periods on record in 2010 and 2011, but then came yet another intense drought from 2017 to the present. In fact, 2018 and 2019 were Australia’s hottest and driest years on record. On December 18, the continent had its hottest day on record, with an average high temperature of 107.4 degrees F. California experienced a similar “weather whiplash,” swinging from record-breaking drought in 2012–2016 to a very wet rainy season in 2017–2018. That combination generated growth of new plants that were subsequently dried out by record heat, creating fuel for the state’s record 2018 wildfire season.
California’s drought was made worse by a persistent high-pressure system off the coast known as the “ Ridiculously Resilient Ridge.” That high-pressure ridge diverted storm systems to California’s north, leading to years of low precipitation. Researchers have suggested that climate change may cause such blocking systems to form more frequently. A 2018 study led by UCLA’s Daniel Swain found that as temperatures continue to rise, California will see a shift to less precipitation in the spring and fall and more in the winter, lengthening the wildfire season.
The situation in Australia is again strikingly similar to that in California. Researchers have shown that global warming is expanding an atmospheric circulation pattern known as the Hadley cell. This circulation is caused by hot air at the equator rising and spreading toward the poles, where it begins to cool and descend, forming high pressure ridges. In Australia, this process creates what’s known as the subtropical ridge, which as CSIRO notes, has become more intense as a result of global warming expanding the Hadley cell circulation. A 2014 study, CSIRO’s David Post and colleagues reported that stronger high-pressure ridges have been decreasing rainfall in southeastern Australia in the autumn and winter. The significance? The lack of rainfall creates more dry fuel for fires and lengthens the bushfire season.
Based on this scientific research, the latest IPCC report found in 2014 that “fire weather is projected to increase in most of southern Australia,” with days experiencing very high and extreme fire danger increasing 5-100% by 2050. And a 2015 CSIRO report concluded, “Extreme fire weather days have increased at 24 out of 38 Australian sites from 1973-2010, due to warmer and drier conditions … [forest fire danger index] increase across southeast Australia is characterised by an extension of the fire season further into spring and autumn … partly driven by temperature increases that are attributable to climate change.” |
