evidence: The planet is well on the path to devastating climate change. In 2019, Australia’s warmest year on record, average surface temperatures were 1.1°C above the pre-industrial period. Australia has warmed on average by 1.4°C since national records began in 1910. Current global and Australian policies to reverse this trend are inadequate. We must plan to do better and prepare for the worst. Predicting how Australia will change at or beyond 3°C of global warming is challenging. However, by using multiple lines of evidence, such as computer modelling of the climate system, observed changes, and historical paleoclimate studies, we can develop an understanding of future temperatures as well as where we may reach irreversible ‘tipping points’—passing thresholds that trigger sudden and accelerating changes in larger climate systems—and how to mitigate those risks. [...] Australia’s natural resources are directly linked to our wellbeing, culture and economic prosperity. Yet our ecosystems have already been transformed due to a global increase of 1.1°C in average temperature since the late 19th century, with severe consequences for thousands of species.