Human-caused global heating made the intense heatwave that affected much of Australia in early January five times more likely, new analysis suggests.
The heatwave earlier this month was the most severe since the 2019-20 black summer, with temperatures over 40C in Melbourne and Sydney, even hotter conditions in regional Victoria and New South Wales, and extreme heat also affecting Western Australia, South Australia and Tasmania.
In Victoria, the heat preceded bushfires that burned through 400,000 hectares and destroyed almost 900 buildings.
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A report by World Weather Attribution (WWA) suggests that the effect of greenhouse gas emissions outweighed the effects of a weak La Niña, which usually means milder temperatures across most of mainland Australia.
The report’s authors suggest that the climate crisis made the extreme heat about 1.6C hotter, while the La Niña likely lowered maximum temperatures by between 0.3 and 0.5C.
“There was definitely a signal of human-induced climate change behind this event,” said report co-author Prof Sarah Perkins-Kirkpatrick, a climate scientist at the Australian National University.
Heatwaves – defined as three consecutive days where maximum temperatures are higher than average – cause more deaths in Australia than all other natural hazards combined.
“When people are affected by extreme heat, it is very insidious,” Perkins-Kirkpatrick said. “It’s not something that happens straight away … it’s something that comes to light in a number of days after the event, and may also be due to the exacerbation of underlying diseases.”
“The mentality here of ‘suck it up, she’ll be right’ does not fly any more,” she said. “[The heat] is getting worse and whether we like it or not … there’s ultimately a limit to what we can actually physically cope with.”
Perkins-Kirkpatrick added that the “temperature profile and also the driving weather system” for January’s extreme heat was reminiscent of the 2009 south-east Australian heatwave, which “exacerbated adverse bushfire weather during that time”.
In the current climate, Australians should expect heatwaves similar to the January event about once every five years, the analysis suggests. The report’s authors warn that similar heat events could be expected every second year if the world warms 2.6C above the preindustrial average, which is predicted to be reached by the end of the century based on current carbon emissions.
WWA co-founder Friederike Otto, a professor of climate science at Imperial College London, said: “As extreme heat is one of the deadliest extreme weather events that is changing very fast with global warming … it is important to highlight these rapid changes, even if the results are not surprising at all.”
WWA, an international collaboration of scientists, uses weather observations and climate models to analyse the role human-caused global heating plays in extreme weather events.
Otto noted that while the techniques the group uses are well established, “as we make the results available in the days and weeks after the event, the [heatwave] study itself is not peer reviewed yet”.
