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| Farmer Richard Gillham drives his truck across a dry paddock as he feeds sheep on his property at Boggabri. The Australia Institute says summer temperatures are lasting a month longer than they did in the mid-20th century. Photograph: David Gray/Getty Images |
The discussion paper, to be released on Monday, said that trend was “highly likely” to continue and would bring with it longer and hotter bushfire seasons, more heatwaves, while agricultural crops will be damaged, livestock will suffer and entire ecosystems will be placed at risk.
“If it feels like Australian summers are getting longer and hotter, that is probably because they are,” the report said. “The summers many Australians grew up with no longer exist.”
The researchers Tom Swann and Mark Ogge examined Bureau of Meteorology (BoM) temperature data from 70 weather stations across the country to compare daily average temperatures over the past two decades with an earlier mid-20th century benchmark.
They found that between 1999 and 2018 Australia experienced summer temperatures for a full 31 days longer, compared to a benchmark between 1950 and 1969, while winter temperatures lasted 23 fewer days over the same comparative periods.
Over the past two decades, summer was on average a month longer than it was in the mid-20th century. The report said temperatures that “marked the start of summer now come around two weeks earlier”, and “temperatures that marked the end of summer now come around two weeks later”.
Last month, the Bureau of Meteorology confirmed 2019 was Australia’s hottest year on record, although the Australia Institute report was unable to include 2019 data in its analysis.
The researchers also narrowed in on temperatures over the past five years, measured against that same 1950-1969 benchmark, and found that summers were now on average close to 50% longer. “These most recent summers were twice as long as the most recent winters,” the report added.
Examining the data, the discussion paper said that while in “every capital city, summers have grown longer and winters have grown shorter”, there was evidence of even larger changes in regional areas.
For example, the report said that summers were 48 days or seven weeks longer in Port Macquarie, and that the length of winter had halved in seven areas across the country.
Meanwhile, summers were now 38 days longer in Melbourne, 36 days longer in Adelaide, and 35 days longer in Hobart and Perth. In Sydney, summer was now 118 days, 28 days longer than it had been on average in the mid-20th century.
Although they say that “caution is needed extrapolating to the future from past observations, especially over short time frames”, the researchers said it is “highly likely over the medium and longer them that summers will continue to get longer and hotter”.
“These trends are likely to continue indefinitely unless greenhouse gas emissions are decisively reduced, ultimately to net-zero,” the report said.
Richie Merzian, the Australia Institute’s climate and energy program director, said longer summers and shorter winters would leave less time for authorities to enforce bushfire management strategies.
He said that Australia was currently experiencing 1C of global warming, but that the government’s current emissions reduction targets are “aligned with 3 to 4C of warming, which leaves young Australians facing ever lengthening summers with significant consequences”.
The researchers drew on data from weather stations in subtropical and temperate areas across southern Queensland and Western Australia, New South Wales, Victoria, the Australian Capital Territory, South Australia and Tasmania.
The discussion paper adds to analysis showing the impact of the climate crisis on Australia’s summers.
A Victorian CFA and BoM study released last year found that global heating was in part responsible for the increased length of bushfire seasons, while a 2017 ANU study found that even if the Paris agreement targets were met, summer heatwaves in major Australian cities were likely to reach highs of 50C by 2040.
Links
- Morrison a ‘predatory’ centrist on climate policy with no plans for meaningful emissions reduction, says Swan
- Collinsville: the Queensland town on the frontline of the coal wars
- Explainer: what are the underlying causes of Australia's shocking bushfire season?
- 2019 was Australia's hottest year on record – 1.5C above average temperature
- Too hot for humans? First Nations people fear becoming Australia's first climate refugees
- Leading scientists condemn political inaction on climate change as Australia 'literally burns'
- What are the links between climate change and bushfires? – explainer
- Stripped bare: Australia's hidden climate crisis
- 'I don't know how we come back from this': Australia's big dry sucks life from once-proud towns
- Australia's summer outlook: soaring temperatures and bushfire risk
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