La Niña brings wet, cool shift
La Niña has broken Australia’s hot streak, delivering the wettest summer in four years and its coolest in almost a decade.
Australia’s rainfall in 2020/21 is 29 per cent above the long-term average, with the Murray-Darling Basin receiving 13 per cent above average rain
“La Niña cycles are really important in Australia for breaking droughts by bringing heavy, soaking rain,” says Australian National University climatologist Nerilie Abram.
Meanwhile, Australia's average temperature this summer was .06 degrees Celsius warmer than average, however, it was still cooler than the past eight years, which have included the four hottest summers on record.
“It was 1.8 degrees Celsius colder this summer compared to last summer,” says senior climatologist Bureau of Meteorology climatologist Simon Granger.
“That's quite a substantial change.”
The cooler temperatures were driven by the high rainfall delivered by La Niña.
“When we've got a lot of rainfall and we've got lots of vegetation growth, lots of soil moisture, what that means is firstly there's a lot of clouds, so we don't get as much solar energy,” Dr Abram said.
“Energy that does arrive to the surface is able to cause evaporation which prevents the temperatures from getting as warm as they otherwise would.
“In a La Niña year, globally, the temperature will be a bit cooler compared to an El Niño year.”
But despite the La Niña effect, January has been the sixth hottest globally since records began.
Mean temperatures in Australia were still slightly higher than the long-term average, even though the nation saw the coolest summer in nine years.
“The effect of La Niña, in terms of being able to counteract the warming of the climate system, is becoming less and less,” said Dr Abram.