South Eastern capitals face 50 degree days

Climate chaos0
From the Australian

MELBOURNE, Adelaide and Sydney will blister in temperatures of more than 50C by 2050, according to the first hard look at the impact of climate change on extreme weather.

The forecast is part of a long-term prediction that temperatures on the hottest day of the year will rise dramatically in parts of southern Australia, including the southern Murray-Darling Basin, much of coastal NSW, Victoria and South Australia.

But the study did not find evidence that other parts of Australia would be so severely affected.

“No one’s ever looked at these numbers before,” said Andy Pitman, co-director of the University of NSW Climate Change Research Centre in Sydney.

Scientists with the CSIRO and the Australian Bureau of Meteorology have also assessed the nation’s future climate but they focused on average changes in extremes of temperature and rainfall due to climate change.

Along with graduate student Sarah Perkins, Professor Pitman analysed daily temperatures. “There is nothing wrong with what they did, but they missed that last bit of evidence that identified the ‘extreme’ extremes,” Professor Pitman said.

The researchers first tested the effectiveness of many climate modelling systems by “hind-casting”, testing how well they predicted past conditions.

After identifying the most reliable models, they simulated daily changes in temperature and rainfall as greenhouse gases increased in the atmosphere. They found the increase altered the pattern of warming for rare super-hot days.

To their surprise, there was also an indirect effect. Global warming led to a reduction in rainfall which, in turn, reduced evaporation. “If there’s less evaporation, the land surface becomes hotter, a process known as positive feedback,” Professor Pitman said.

That is why extreme events in places such as Darwin and Perth did not outpace those in the south: there’s no feedback there.

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