THE rise in extreme temperatures in Australia because of climate change may not be quite as big as some feared but it will still cause grave problems for human health, infrastructure, animals and plants, a study by scientists from the University of NSW finds.
The researchers tested the accuracy of climate models used by the United Nations' peak scientific body, the Intergovernmental Panel on Climate Change, comparing them with actual climate observations.
When the poorly performing models were removed, the predicted rise in temperature extremes was between 2 and 3 degrees by the end of the century rather than 3 and 5 degrees as the modelling had predicted, according to the study published in the journal Geophysical Research Letters.
But one of the authors, Andy Pitman, said the research should not be interpreted as diminishing the climate change problem for Australia.
He said the study found the 2- to 3-degree temperature rise would generate even fiercer heatwaves than Victoria and South Australia had this year and would have a big impact on human health and the ability of societies to cope.
"The lower figures are not as bad as 3 to 5 degrees but they're still very bad and emphasise the need to aggressively cut greenhouse gases on a global scale," Professor Pitman said.
"A 2- to 3-degree rise in the mean temperature, which people have been talking about for a long time, is important.
"But a 2- to 3-degree rise in a temperature that occurs once every 20 years is really scary," he said.
Professor Pitman said the report this week by Victoria's chief health officer on the heatwave that preceded the state's bushfires pointed to the dangers of the temperature rises when they came on top of extreme events such as heatwaves.
The report found there were 374 more deaths in the state's heatwave than would normally be expected at that time of the year.
The figure is more than double the number of deaths caused by the bushfires.
State ambulance services experienced a 34-fold rise in cases with direct heat-related conditions and nearly a three-fold increase in cardiac arrest cases.
There was almost a three-fold rise in the number of patients who were dead on arrival at emergency departments, and an eight-fold increase in direct heat-related cases.
Temperatures were 12 to 15 degrees above normal for much of Victoria during the heatwave.
"What we are saying is that with global warming, those temperatures that are rare, like those in Melbourne, will be 3 degrees warmer," Dr Pitman said.
"That has really major impacts on infrastructure, power grids and human health.
"A lot of systems out there are not built to withstand a 47-degree day in Sydney."
The models used in the UNSW study were based on projections that greenhouse gases would keep rising.
Global emissions are rising faster than those projections but Dr Pitman said he hoped that trend would slow and emissions would be cut.
"If we are stupid enough as a planet, to continue to track well above this, we are going to get worse consequences," he said.
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