Record hot years such as last year's global scorcher will become the norm before 2030 unless greenhouse gas emissions are curbed, a new study by Australian researchers has found.
The scientists, led by Sophie Lewis from the Australian National University, used different emissions projections to determine when 2015's record global surface temperatures could be considered a "new normal".
Most of the climate models analysed that, within a decade, last year's record would be average or even cooler than average, Dr Lewis said.
"The studies are quite sobering and show us what will happen if we're not prepared to make the deep cuts to emissions," she said.
At a regional level, Australia's "angry summer" of 2013 - which smashed many previous records and was notable for extreme heatwaves and widespread bushfires - could become a typical event in less than 20 years, she said.
"We're seeing a lot of extremes but that's the part of the climate system that we're vulnerable to," Dr Lewis said. Daytime temperatures of 50 degrees could be experienced during summers in Melbourne, Adelaide and Perth, while the mercury in Sydney and Canberra will nudge 45 degrees during extreme periods, she added.
'We expect land surfaces to warm up faster than the oceans - and there's a lot of interior in Australia that can warm quite quickly," she said. "We also expect polar regions to warm faster than the tropics - [so] it looks like Australia could have those extremes a little earlier than North America, Asia or Europe."
The paper came out on Monday, the day national leaders and delegations are gathering in the Moroccan city of Marrakesh to discuss the implementation of the climate agreement agreed late last year in Paris. That agreement came into force on Friday after almost 100 nations - but not yet Australia - had ratified the deal.
Australia may ratify the agreement before the Marrakesh meeting ends on November 18. The Turnbull government is likely to face stiff questions at the event over the adequacy of Australia's goal of cutting 2005-level emissions by 26 per cent to 28 per cent by 2030, and whether its policies offer a plausible path to that target.
While 2015 beat 2014 as the hottest year since reliable data records began in the 1880s, the odds strongly favour the bar being set even higher this year.
Dr Lewis noted that natural variations - such as the big El Nino event last year in the Pacific - meant the public should not expect every month or year to break new global heat records.
"We're not expecting every year to be hotter than the previous one but the trend should be for us to be experiencing more extremes," she said.
"The median time of emergence of 2015 as the new norm occurs between 2020 and 2030 under all emissions trajectories," the paper found.
(See chart below of observations and the forecast warming of four main carbon emissions scenarios, with RCP8.5 the highest.)
The paper aimed to provide a technical definition for determining the "new normal", a term regularly bobbing up in science and public discussion around extreme climate events. (See Tweet below for a recent example:)
Global temperatures are now running more than 1 degree above pre-industrial-era levels. In Paris, almost 200 nations agreed to keep temperature increases to less than 2 degrees, with an aim of even 1.5 degrees, in order to avoid dangerous climate change.
Dr Lewis was also critical of people such as Senator Malcolm Roberts who on Monday launched a report titled: "On climate, CSIRO lacks empirical proof."
"We're trying to communicate the need to pay attention and adapt," Dr Lewis said. "There's a certain amount of warming already locked in, and we should be preparing.
"But as a community we're not likely to be taking this seriously if we're hearing influential voices that it's not a problem and that it's been falsified," Dr Lewis said. "So it's really dispiriting."