Australia’s south-east has just experienced some of the hottest September days on record, but experts say worse weather could be yet to come as the chances of a hot and dry summer increase.
Sydney’s Observatory Hill weather station set or equalled several temperature records over the past week. Olympic Park in Melbourne and West Terrace in Adelaide have also seen maximum temperatures among the top 10% ever recorded in recent weeks. All three cities have records stretching back more than 100 years.
Temperatures have eased off in parts of Adelaide and Melbourne, but forecasts predict the unseasonably hot weather will return.
The Australian Bureau of Meteorology declared on Tuesday that Australia is now in an El Niño climate pattern. El Niño has been linked with increased drought, heatwaves and bushfires in Australia.
BoM also confirmed a positive Indian Ocean Dipole – determined by differences in sea surface temperature between the eastern and western Indian Ocean – is under way. A positive IOD usually results in decreased spring rainfall for central and south-east Australia.
“Without climate change, we would still expect this summer to be hot and dry because of El Niño and the positive [Indian Ocean Dipole],” says Prof Sarah Perkins-Kirkpatrick, a climate scientist at the University of New South Wales.
“However, because Australia’s warmed by almost 1.5 degrees celsius, it’s going to be that much worse.”
Some of this increasing trend can be seen in the number of hot days and heatwaves Australia has experienced over time. Guardian Australia compared the maximum temperature at Observatory Hill each day to the long term average – one that stretches back over a hundred years.
Days with a max temperature in the top 10% of temperatures were classified as hot. A span of three or more consecutive days in the top 10% were classified as heatwave days. As average temperatures have increased, it appears more and more days surpass these thresholds.
The number of hot and heatwave days since the start of the year doesn’t come close to what was experienced during the same period in 2019. During 2019-20, Australia saw the huge black summer bushfires.
But Perkins-Kirkpatrick says what Australia is experiencing now is unlike what we saw in 2019.
“It sort of started off in a different way this summer compared to black summer. So black summer, there was that three year drought leading into summer. This summer, because we’ve had the back-to-back La Niñas, there’s a little moisture in the system.”
“But that could very well change very quickly. Because we have got an El Niño now, and a positive IOD as well.”
“So those combined will mean hot and dry conditions on top of background warming, which is a very precarious position to be in.”
