Third-warmest and fourth-coldest? Canberra’s year of extremes

Early morning trackwork on a sub-zero winter morning at canberra’s Thoroughbred Park race course. Photo by Karleen Minney.The days were warmer and the nights were colder in 2017 during a year of extremes for Canberra.

As much of eastern Australia endured record heat, the territory had its third-warmest year on record – and its lowest annual rainfall since 2009 – in what was also the third-warmest year for Australia overall.

Yet the Bureau of Meteorology’s annual report revealed last winter was actually Canberra’s coldest since 1982, and its fourth-coolest on record.

The capital shivered through 109 nights below 2 degrees in 2017, 16 more than average. That included a memorably frosty morning on July 1, when the mercury plunged to minus 8.7 degrees in the coldest temperature recorded in almost fifty years.

After a consistently wet 2016, Bureau climatologist Dr Linden Ashcroft said 2017 brought “a lot of variability” to the nation’s capital.

“It was frostier than usual this winter, even for Canberra,” she said. “But it was also very dry and very warm.”

The year kicked off to a steamy start, notching up its warmest mean temperature for January ever recorded at 32.8 degrees.

Daytime temperatures for every month except April also hit their top ten warmest, and over summer, 46 nights failed to drop below 15 degrees, compared to an average of 29 nights.

Canberra’s hottest day for 2017 came on February 11 with a high of 41.6 degrees but 56 days in total reached at least 30 degrees.

That’s more than the long-term average of 33 days, but on par with recent years, which have seen global warming trends continue to drive up temperatures around Australia.

“We also had a really interesting warming event in September where Canberra hit 30 degrees on the 23rd, that’s it’s hottest day for that [time of year] ever,” Dr Ashcroft said.

“So that was interesting. Scary but interesting.” So what was up with that winter?

A lack of rainfall in the territory meant lots of cold, cloudless nights come winter, Dr Ashcroft said, as heat from the day escaped.

“But, counter-intuitively frost can also show the fingerprints of climate change,” she said.

A recent study by researchers at the bureau linked clear winter nights to the movement of high pressure systems carrying rain further south.

“And that’s consistent with what climate models say will happen in a warming world,” Dr Ashcroft said. How did the rest of Australia fare?

For the nation, 2017 was also the third-warmest on record, with the eastern half including NSW and Queensland notching their hottest annual readings.

Only 2013 and 2005 were warmer years in records going back to 1910.

“Australia has warmed by about one degree since the middle of the 20th century,” Dr Ashcroft said.

Our unusually warm temperatures were in line with global ones. In the coming weeks, Dr Ashcroft said international agencies will likely confirm 2017 as the second or third-warmest on record based on average land and sea-surface temperatures going back to the 19th century.

The great majority of scientists attribute the rise in global temperatures to an increase in greenhouse gas emissions.

“This year is even more interesting because it’s the first we’ve seen globally without an El Nino event, which has always been linked to our warmest years,” Dr Ashcroft said. What about 2018?

As for what this year has in store for Canberra, Dr Ashcroft said more rain could be on the cards.

“There’s a La Nina system happening and that usually means slightly wetter than average and it can mean slightly cooler than average too, but the system is quite weak,” she said.

“The models are suggesting this will not kick on for much longer than early autumn.”

The year began in much the same fashion as the last with a run of hot days, climbing into 40 degrees, followed by lashing wind and rain on Tuesday afternoon.

Wednesday is expected to reach a top of 28, with more rain on the way Thursday.

with Peter Hannam

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