Climate change could sentence Melbourne and Sydney to 50-degree days even if the world meets its Paris climate change targets, a new study warns.
Other Australian cities are also on track for unprecedented extreme heat, a new study led by the Australian National University says.
Lead researcher Dr Sophie Lewis says dramatic changes that will affect the livability of Australia are likely, even under ambitious Paris pact targets to limit global warming to well below 2 degrees Celsius.
Those changes are likely to see Australia smash summer heat records more frequently, she warns.
"One of the hottest years on record globally -- in 2015 -- could be an average year by 2025," she says.
"Major Australian cities, such as Sydney and Melbourne, may experience unprecedented temperatures of 50 degrees Celsius under 2 degrees of global warming.
"The increase in Australian summer temperatures indicates other major cities should also be prepared for unprecedented future extreme heat."
For example, the study's climate modelling projects daily temperatures of up to 3.8 degrees Celsius above existing records in Victoria and NSW, despite the Paris targets.
"Urgent action on climate change is critical - the severity of possible future temperature extremes simulated by climate models in this study poses serious challenges for our preparedness for future climate change in Australia," Dr Lewis warns.
Researchers used a combination of observations and modelling to assess how record-breaking events may change in the future.
The research, supported by the Centre of Excellence for Climate System Science, has been published in Geophysical Research Letters.
HuffPost Australia profiled Sophie Lewis for our Breaking The Ice podcast series on climate science. You can learn a little more about her fascinating personal story here, or listen to the podcast below.