Year of extremes

In 2020, Australia’s climate had more plot twists than an episode of Tiger King.

From bushfires that ravaged the country to extreme hailstorms, scorching heatwaves and home-threatening coastal erosion events, the nation saw it all.

Now, scientists from Australia’s Bureau of Meteorology (BOM), have summarised the past year’s events in their Annual Climate Statement.

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Snapshot: report key points

• 2020 was Australia’s fourth warmest year on record with an average mean temperature of 1.15°C above the 1961–90 average
• A La Niña was declared by BOM in September and is currently around its peak
• Rainfall was slightly – 4% – above average
• The Murray-Darling Basin water storages saw significant increases, with levels rising from 36.8% in March to 68.8% at the end of November

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They report that despite being a La Niña year – which typically reduces temperatures – 2020 was Australia’s fourth-warmest year on record, with an average mean temperature of 1.15°C above the 1961–90 average.

“We know that Australia is affected by climate change,” explains Lynette Bettio, senior climatologist at the Bureau of Meteorology in an AusSMC briefing.

“Every year since 2013 has been in Australia’s ten warmest years on record. We are seeing that rise in temperatures.”

Mean annual maximum and minimum temperatures were above average in all states and the Northern Territory.

Daytime temperatures were especially warm for Sydney, Hobart and Darwin. All capital cities, excluding Adelaide, observed warmer than average annual mean minimum temperatures.

The Statement also notes that nights were particularly warm in Sydney, Darwin, Hobart, Canberra and Brisbane. 

“It’s a tricky one to call the entire year a La Niña year,” explains Andrew Watkins, Head of BOM’s Operational Climate Services.

“La Niña did start pretty late this year. The cooling influence of the La Niña arguably didn’t kick in until September, October or so.”

The national rainfall picture was more of a mixed bag. Rainfall for 2020 was close to average (just above by 4%), easing drought conditions in many areas of the nation. 

“We know how 2020 started off with those extreme bushfires,” says Bettio. “With extreme drought and heat. We did see some relief from that in those earlier months. We ended the year wet, with December being one of Australia’s wettest on record.”

In the Murray-Darling Basin, southern water storage levels increased from 36.8% in March to 68.8% by the end of November. In the northern Basin, storage levels increased from a record low of 5.4% to around 25% at the end of December.

However, Bettio highlights that some regions still received below-average rainfall, including the west of Western Australia and southeast Queensland, didn’t receive any “real relief” from the long-term drought.

“We’re really looking for more months, even years of increased rainfall to really restore the environment and help out with those water storages. But there has been some relief in 2020,” he says.

Watkins explains there are a combination of factors that led to 2020’s climate.

The development of a brief negative Indian Ocean Dipole in August saw an increased chance of rainfall from July onwards. In 2019, a positive Indian Ocean Dipole was the dominant driver that kept things dry and hot across the year. 

Down in the Southern Ocean, we saw a positive Southern Annular Mode (SAM) develop, leading to more onshore flows from the Tasman Sea, bringing moisture and more rainfall while also keeping our skies cloudier and the temperatures down.

“Of course, behind all this there’s always that factor of climate change which in the central months of the year, the cooler months in southern Australia, tends to keep things drier,” explains Watkins.

“Generally, we’ve seen that warming trend of Australia of about 1.44 degrees over the past century.”

As for this year, Watkins was cautious about forecasting 12 months in advance. However, he does explain that models are suggesting more neutral conditions by the first half of the year.

“All the models are suggesting we’re going to swing away from the La Niña event and back to something more neutral for the first half of the year,” Watkins says.

“That doesn’t mean we won’t see above average rainfall… something easing away from La Niña anyway.”

The full report is available online at the Bureau of Meteorology website.