Human-caused global warming made the intense heatwave in Australia this January five times more likely, new research shows. The early January heatwave was the harshest since the 2019-20 black summer, with temperatures soaring above 40C in Melbourne and Sydney. Regional parts of Victoria and New South Wales faced even hotter conditions. Extreme heat also affected Western Australia, South Australia, and Tasmania. In Victoria, the heat came before severe bushfires that burned 400,000 hectares and destroyed almost 900 buildings. A report from World Weather Attribution (WWA) says greenhouse gas emissions had a stronger effect on the heatwave than the weak La Niña, which typically cools mainland Australia. The study’s authors estimate climate change boosted the heat by about 1.6C, while La Niña lowered temperatures by 0.3 to 0.5C. Prof Sarah Perkins-Kirkpatrick, a climate scientist at Australian National University and report co-author, said, "There was definitely a signal of human-induced climate change behind this event." Heatwaves, defined as three days of above-average temperatures, cause more deaths in Australia than all other natural disasters combined. Perkins-Kirkpatrick added, "When people are affected by extreme heat, it is very insidious. It’s not something that happens straight away… it comes to light days after the event, often due to worsening of existing health conditions." She stressed, "The mentality here of ‘suck it up, she’ll be right’ does not fly any more. The heat is getting worse and there’s ultimately a limit to what we can physically cope with." The weather pattern of January’s heat resembled the 2009 south-east Australian heatwave, which worsened bushfire conditions then. Now, Australians can expect heatwaves like January’s about once every five years. The report warns that if global temperatures rise 2.6C from preindustrial levels by century’s end, such heatwaves may occur every second year. WWA co-founder and Imperial College London climate professor Friederike Otto said, "Extreme heat is one of the deadliest extreme weather events changing rapidly with global warming. It’s important to highlight these fast changes, even if the results are not surprising." WWA uses weather data and climate models to study human impacts on extreme weather. Otto noted that while their methods are well established, this heatwave study is yet to be peer reviewed.