Australia has just experienced its most severe heatwave since 2019, when extreme weather conditions helped fuel the catastrophic Black Summer bushfires. Between 7 and 9 January, maximum temperatures across southeastern Australia remained persistently above 40°C, with Melbourne recording a peak of 44.4°C on 9 January.
Scientists from the World Weather Attribution initiative examined observational data and climate model simulations to assess how rising global temperatures influenced the event. Their analysis compared current climate conditions — which are around 1.3°C warmer than the late 19th century — with a world unaffected by large-scale fossil fuel use.
The researchers found that climate change not only increased the likelihood of the heatwave but also intensified it, adding an estimated 1.6°C to the temperatures experienced during the event.
Heat extremes accelerating despite La Niña
The findings were particularly striking because the heatwave occurred during a La Niña phase, a climate pattern that typically brings cooler and wetter conditions to much of Australia.
"To see heat of this magnitude developing under La Niña conditions is remarkable," said Ben Clarke, a climate researcher at Imperial College London and one of the study's authors.
According to the analysis, heatwaves of this severity — once expected roughly once every 25 years — are now likely to occur every five years. If global temperatures rise by a further 2.6°C above pre-industrial levels, such events could become biennial.
"The evidence is overwhelming," Clarke said. "Extreme heat is shifting from an occasional extreme to a near-regular feature of the Australian summer."
A mounting threat to public health
Heatwaves are already Australia's deadliest natural hazard, responsible for more deaths since 1900 than bushfires, floods, cyclones and earthquakes combined.
Extreme heat poses the greatest risks to older people, outdoor workers, those with existing health conditions and communities facing socioeconomic disadvantage. The strain on public services is growing: one Melbourne hospital reported a 25 per cent increase in emergency admissions during the January heatwave.
Health experts also warn that prolonged heat is exacerbating mental health challenges, particularly during back-to-back extreme weather events.
Dangerous conditions spreading nationwide
The analysis comes as northern parts of Western Australia recorded temperatures as high as 50°C this week. Meanwhile, a severe heatwave is developing across central and southern regions and is forecast to move eastward, pushing temperatures beyond 40°C and significantly increasing fire danger over the weekend.
Bushfires reignited under extreme heat
The heatwave created ideal conditions for bushfires to spread rapidly across the southeastern state of Victoria, where authorities declared a state of disaster. By 14 January, fires had burned approximately 404,000 hectares — more than five times the size of Singapore — destroying over 700 structures, including 228 homes.
Australia has a long history of major bushfire disasters, including events in Canberra in 2003, Victoria in 2009, Tasmania and the Blue Mountains in 2013, and the devastating 2019–20 Black Summer fires. That season burned around 24 million hectares, destroyed thousands of buildings, killed more than 30 people and affected an estimated 3 billion animals.
Scientists have repeatedly warned that continued fossil fuel use will make such disasters more frequent and intense. Recent research has also raised concerns that future fires could increasingly threaten urban areas, echoing the destruction seen during last year's wildfires near Los Angeles.