02/01/2021

(AU) Australia Records Fourth-Warmest Year In 2020, Despite La Niña

The Guardian - 

Climate scientist says another top 10 year is a ‘no shit, Sherlock’ moment, as temperatures across the country were 1.15C above average

Ploughing near Gunnedah in north-west New South Wales in May. La Niña brought much-needed rain to parts of Australia in 2020, but it was still the fourth-warmest year on record.  Photograph: Mark Kolbe/Getty Images


Last year was the fourth warmest on record for Australia, continuing a run of record warm years over the past decade, according to provisional data released by the Bureau of Meteorology.

Across the country, temperatures in 2020 were 1.15C higher than average, putting the year behind 2005, 2013 and 2019, which remains the hottest year on record.

The data is gathered from the bureau’s ACORN-SAT dataset that takes readings from 112 weather stations across the country and goes back to 1910.

Eight of the 10 hottest years on record for Australia have occurred since 2013, the data shows. Climate scientists said the heat was driven by human-caused climate change.

Dr Sarah Perkins-Kirkpatrick, a climate scientist at the University of New South Wales specialising in extreme events, said human-caused climate change had reliably delivered another top 10 year.

The hottest and driest year on record remains 2019, when mean temperatures were 1.52C above the 30-year average taken between 1961 and 1990.

Australia experienced droughts, heatwaves and devastating bushfires that carried on into 2020.

In March, abnormally high sea surface temperatures across the Great Barrier Reef caused the third mass coral bleaching event in five years.

The hottest spring on record occurred in 2020, with temperatures 2.03C above average. That ended with a November 2.47C warmer than average – the hottest November on record.

The bureau will check the latest provisional data before making a formal climate statement on 8 January.

The bureau declared a La Niña event in September and in late December said its influence was likely reaching its peak, with climate models suggesting a return to neutral conditions around late summer or early autumn.

La Niña is the cooler phase of a cycle known as Enso (El Niño Southern Oscillation), with the warmer phase known as El Niño.

Blair Trewin, senior climatologist at the bureau, told Guardian Australia La Niña’s influence on temperatures tended to come the year after the phenomenon was declared.

But he said: “Clearly 2020 was significantly warmer than a normal year. But it was a return to some level of normality after an exceptional 2019.”

While November was a record hot month, Trewin said it was likely that December had been relatively cool.

Rainfall and cloud cover in the north-west and central parts of the country had brought temperatures down.

Across the year, Trewin said, the underlying warming trend expected from human activity was the main driver of the higher temperatures.

La Niñas are associated with lower ocean temperatures in the tropical Pacific and can bring higher rainfall for northern, eastern and central parts of the country, as well as cooler daytime temperatures.

The provisional data shows the previous hottest year to be associated with a La Niña was 1998, when Australian temperatures were 0.97C above average.

The most recent year that temperatures failed to get above the 1961 to 1990 average was 2011 – the middle year of a La Niña that spanned three years.

Perkins-Kirkpatrick said the record hot November had been a surprise because it was expected that La Niña would have kept temperatures lower.

She said: “2019 was in a league of its own and 2020 I think was not as extreme. The tone for the year was far more placid.

“Even with a La Niña end to the year, La Niñas now are warmer than El Niños were without climate change. We are seeing each year come into the top 10, and each year will shift ever warmer.”

She said human activity – mainly from burning fossil fuels that were loading the atmosphere with extra carbon dioxide – was generating the extra heat.

“It is absolutely us causing this warming. It couldn’t be occurring naturally.”

In December the World Meteorological Organization released a preliminary report saying 2020 was likely to be among the three hottest years globally, using an average across five global temperature datasets.

The UN agency said the warmth of 2020 would mean the past six years were likely to be the six warmest years on record.

Bureau of Meteorology Climate and Water Outlook

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