New Australian research has found temperatures reached during the hottest year on record globally (2015) could be just an average year by 2025. But all hope is not lost - that's just if carbon emissions continue to rise at the same rate.
Lead researcher Dr Sophie Lewis said human activities had already locked in this new normal for future temperatures, but immediate climate action could prevent record extreme seasons year after year.
"If we continue with business-as-usual emissions, extreme seasons will inevitably be the norm within decades and Australia is the canary in the coal mine that will experience this change first," said Dr Lewis from The Australian National University (ANU) and the ARC Centre of Excellence for Climate System Science.
The idea of a new normal has been used repeatedly when talking about climate change but had never been clearly defined until Dr Lewis and colleagues developed a scientific definition for the term.
"Based on a specific starting point, we determined a new normal occurred when at least half of the years following an extreme year were cooler and half warmer. Only then can a new normal state be declared," Dr Lewis said.
This process was also used to determine new normal conditions for seasonal and regional changes to the climate, she said.
Using the National Computational Infrastructure supercomputer at ANU to run climate models, the researchers explored when new normal states would appear under the Intergovernmental Panel for Climate Change's four emissions pathways.
The research team examined seasonal temperatures from December to February across Australia, Europe, Asia and North America.
"The results revealed that while global average temperatures would inevitably enter a new normal under all emissions scenarios, this was’t the case at seasonal and regional levels," Dr Lewis.
"We found that with prompt action to reduce greenhouse gases a new normal might never occur in the 21st century at regional levels during the Southern Hemisphere summer and Northern Hemisphere winter."
The research, supported by the ARC Centre of Excellence for Climate System Science, is published in the Bulletin of the American Meterological Society.