Australia’s posted its third-warmest year on record in 2017, with the eastern half including NSW and Queensland notching their hottest annual readings.
The Bureau of Meteorology’s annual report showed the nation’s area-averaged mean temperatures – taking in daily highs and lows – were 0.95 degrees above its 1961-90 baseline at 22.75 degrees.
Only 2013 and 2005 were warmer years in records going back to 1910.
Just two of the 17 years since 2001 have reported cooler-than-average years, a trend that reveals a clear signal of the background warming from climate change, Karl Braganza, head of climate monitoring at the bureau, said.
Average land and sea-surface temperatures have risen about 1 degree over the past century both for Australia and the globe overall.
“That means odds favour warmer-than-average temperatures more often than in the past,” Dr Braganza said.
“When conditions are favourable, such as when you have an El Nino [in the Pacific] or when rainfall is lower over the Australian continent, we won’t just get warmer than average conditions, we’ll start to push into one of the warmest years on record, or [get] record-breaking events.”
Some of that potential for heat spikes was on show over the past weekend.
Much of south-eastern Australia soared into the 40s, including 47.3 degrees in western Sydney, making it the second-hottest day in the Sydney Basin on record.
Last year was especially warm for Australia’s daytime temperatures, with average maximums hotter than any year but 2013, coming in at 1.27 degrees above the 1961-90 baseline.
Brisbane clocked up its hottest year on record for maximums, while Sydney, Canberra and Hobart all had one of their top-three warmest years.
Statewide, NSW beat its previous high – also 2013 – by 0.11 degrees with an anomaly for maximums of 1.87 degrees compared with the long-term norm.
Queensland broke its record for maximums by slightly more, beating its previous high mark set in 2013 by 0.13 degrees.
Both states beat their previous highs for mean temperatures too, although just narrowly in NSW’s case.
The heat also brought the second year in a row of mass coral bleaching on the Great Barrier Reef. The unprecedented back-to-back events resulted in the deaths of about half the region’s corals.
Victoria’s readings were less of a stand-out, with 2017 the sixth-warmest for both mean and maximums. It was, though, the 21st year in a row that both temperature measures were above average.
Waters off south-eastern Australia were exceptionally warm in 2017. Photo: Jason South
Western Australia was less remarkably warm compared with most other regions of the country.
The biggest state had only had one year in the past 16 that recorded – narrowly – a below-average year for mean temperatures.
WA was notable, though, for its rain, with 2017 coming in at its ninth-wettest on record.
Nationally, rainfall was about 8 per cent above average at 465.2 millimetres, with the east relatively dry especially in inland regions.
“The middle of the year was notably dry, with June the second-driest on record nationally, and September the driest on record for the Murray-Darling Basin,” Dr Braganza said. “The last three months of 2017 took a wetter turn, with above-average rainfall in many areas.”
For 2017, Australia’s hottest place was Tarcoola in South Australia, which recorded 48.2 degrees on February 9.
NSW had the coolest recording, with Perisher Valley’s minus 12.1 reading on August 27.
Cyclone Debbie helped deliver Queensland two unwanted extremes.
It brought the strongest wind gust of the year with 263km/h recorded at Hamilton Island on March 28, and the wettest day, with 635 millimetres dumped on Mt Jukes two days later.
East Gresford cattle farmers Peter and Rosalie Lawrence were among those battling dry conditions in parts of eastern Australia in 2017. Photo: Max Mason-Hubers
Heating up the greenhouse
Australia’s unusually warm temperatures were in line with global ones. International agencies will likely confirm 2017 as the second or third-warmest on record in coming weeks 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.
These emissions are projected to have risen 2 per cent in 2017 to almost 37 billion tonnes of carbon dioxide-equivalent, resuming their increase after a three-year pause, according to the Global Carbon Budget.
Australia’s emissions have been rising for even longer, increasing each year since 2011 to 550.2 million tonnes in the 12 months to June 2017, the government reported late last month.
The rising trajectory will make it harder for Australia to deliver on its pledge to the Paris climate summit to cut 2005-level emissions by as much as 28 per cent by 2030.
The current La Nina conditions in the Pacific – with the trade winds strengthening and shifting rainfall patterns westward – typically mean above-average rain can be expected for the start of 2018 at least.
The east coast and WA, which may be wetter than normal, face a cooler-than-normal first few months of the year, Dr Braganza said.
“But hot, warmer-than-average conditions are likely from the southern coastal regions, [such as] around Perth, Adelaide, Melbourne and Tasmania,” he said.
This year’s La Nina, though, is relatively weak, and its influence is expected to wane after summer.