Lisa Cox, Sydney Morning Herald
Record temperatures in Australia in 2013 were almost certainly caused by man-made climate change, five separate studies have found.
Researchers from the University of Melbourne, the Australian National University and the University of NSW have concluded it is “virtually impossible” that the heatwaves that hit Australia in 2013 would have occurred were it not for carbon emissions caused by human activity.
The reports have been published in the Bulletin of the American Meteorological Society as part of a global project examining the impact of climate change on extreme weather.
A man enters the baths at Coogee Beach on Tuesday. Photo: Kate Geraghty
The results, which are the strongest statement yet on the impact of climate change on Australia’s weather patterns, are a wake-up call for the Abbott government a week after it was criticised for failing to take beefed-up emissions reduction targets to a special summit of world leaders in New York.
Five teams of researchers examined the heat that baked Australia for much of 2013, leading to the hottest day, month, spring and summer since records began.
They concluded that the record temperatures for the whole of that year would almost certainly not have occurred without man-made climate change and that the chance of heatwaves occurring was more than 2000 times greater because of human-caused climate change.
Professor David Karoly, one of the authors, said the results mark the first time that researchers had concluded that a specific weather event couldn’t or most likely couldn’t have occurred in Australia without the increase in greenhouse gas emissions caused by human activity.
“The Prime Minister last year said that studies hadn’t been done and the CSIRO cautioned against attributing individual extreme weather events to climate change,” Professor Karoly said.
“Now the studies have been done and the results are very clear.”
The teams of researchers used a variety of computer-based simulations that modelled 20th and early 21st century temperatures.
One set of models factored in natural variations in climate and human influences on climate, while another set showed what temperatures would have looked like without man-made climate change.
Out of 12,500 simulated years, only one result in the latter group produced temperatures higher than those seen in Australia in 2005 – the hottest year before 2013 – and none as hot as 2013.
“There was an increase in the frequency of heatwaves in 2013 and the intensity of heatwaves due to climate change,” Professor Karoly said.
“It was three times the frequency and two times the intensity.”