Australia records near-record warmth during the wettest winter since 1996.

Extract from ABC News

ABC Weather

By Ben Deacon

Posted 5 hours ago

Australia's average winter temperature this year was our fourth hottest winter on record.

(Supplied: Bureau of Meteorology)

Australia has just experienced its fourth hottest winter since 1910, according to the Bureau of Meteorology (BOM).

Key points:

• Australia has recorded its fourth warmest winter on record
• It was the wettest winter since 1996
• The warm temperatures are in line with increased temperatures due to global warming 

"It has been generally warm just about everywhere," said Simon Grainger, a senior climatologist with the BOM.

"In terms of mean temperatures, it's been in the top 10 warmest winters on record for every state and territory except Western Australia."

This comes despite neither of Australia's two main climate drivers, El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) strongly favouring above-average temperatures this winter.

 

A lot of Australia saw above-average average daily temperatures this winter. 

(Supplied: BOM)

The national mean temperature for winter was 1.18 degrees Celsius above the 1961 to 1990 average — the fourth-warmest on record after 1996, 2009 and 2013.

The most pronounced warmth was in the northern tropics, where maximum temperatures were about 2C above average.

Nights were warm too

The mean minimum temperature was 1.08C above average, the ninth-highest on record, with the most pronounced warmth in the northern tropics, Tasmania and Victoria.

Much of Australia experienced warmer-than-average minimum overnight temperatures this winter.

(ABC Open: Chris Ferguson)

Mr Grainger said the warmer nights in the south-east were connected to the region experiencing a wetter winter.

"More clouds and more rain keeps more heat in at night," he said.

'The slow creep'

According to Joelle Gergis from the Australian National University, who was also a lead author of the recent Intergovernmental Panel on Climate Change (IPCC) climate change report, Australia's near-record warm winter was an example of what she described as "the slow creep of climate change". 

"We pay attention to these really dramatic weather extremes," she said.

"But meanwhile in the background, like a frog in a pot, we are starting to warm Australia in ways that are really fundamentally changing our seasonal variability."

 

ENSO has been inactive this winter, favouring neither warmer nor cooler conditions.

(Supplied: BOM)

Dr Gergis said this winter Australia had not seen the usual drivers that we would expect to be associated with above-average temperatures.

"So this is background warming that is playing out," she said. 

"The IPCC is saying it's virtually certain that we're going to see a decrease in the intensity and frequency of cold extremes throughout the 21st century, all over the world. 

"And that certainly includes Australia where we've already seen the warming up of our winters.

The BOM said Australia's climate has warmed on average by 1.44C since national records began in 1910.

Wettest winter in 25 years, still below average

Rainfall for winter was the highest since 1996, yet was still 5 per cent below the 1961 to 1990 average.

Mr Grainger said a negative IOD influenced rainfall patterns.

"We did get slightly above-average rainfall over parts of eastern Australia," he said.

"Negative IODs tend to bring increased winter and spring rainfall over eastern southern Australia."

Mr Grainger said the wet weather was greatest in June and July, but less so in August.

"There was a little bit of a weakening in the IOD conditions in August, and certainly compared to 2016, which was one of the strongest negative IODs on record and one of the wettest winters," he said.

"We just haven't seen anything anywhere near as strong nor as wet."

Rainfall for winter was 5 per cent below the 1961–1990 average, but was still the highest since 1996.

(Supplied: BOM)

Wet in the south-west

Mr Grainger said the south-west of Western Australia had a "good old-fashioned wet winter" this year, after a string of dry years. 

"July rainfall in the south-west was 50 per cent above the 1961 to 1990 year average," he said.

"And for that part of the country, it was the wettest July since 1996."

A young girl stands in a flooded backyard in Mundaring, WA after big rains in July.

(Supplied: Ash Lee)

While July's rain meant the winter rainfall for WA's south-west was slightly above average, that's actually only been the fourth time winter rain in the area has been above average since 2000.

The BOM said there has been a decline of about 16 per cent in April to October rainfall in the south-west of Australia since 1970.

Across the same region, May to July rainfall has seen the largest decrease, by about 20 per cent since 1970.