Article by Nick O’Malley and Peter Hannam of the Melbourne Age 10 August 2021
The world is likely to heat to 1.5 degrees or more above preindustrial levels by 2040, exposing it to the sort of extreme weather now ravaging Europe and North America, the most comprehensive analysis yet undertaken of climate change shows.
The latest report by the United Nations Intergovernmental Panel on Climate Change (IPCC) will be central to climate negotiations to be held in Glasgow in November, and confirms the planet is warming in step with rising greenhouse gas pollution.
In 2019, carbon dioxide concentrations were higher than at any time in the past 2 million years, while warming is now occurring at a faster rate than at any time in the past two millennia, the report shows.
‘‘ The urgency is coming through exceptionally strongly in this report, much more so than the previous reports,’’ said Will Steffen, a contributing author on the five previous IPCC assessment reports.
Professor Steffen said unless the world slashed climate emissions by 50 per cent by 2030, it faced an ‘‘ impossible situation’’ .
For Australia, the projections are sobering, in a nation that has already warmed 1.4 degrees since 1910 – a pace in line with the global average for land.
‘‘ Heat extremes have increased, cold extremes have decreased and these trends are projected to continue ,’’ a summary for Australasia states. ‘‘ The frequency of extreme fire-weather days has increased and the fire season has become longer since 1950 at many locations,’’ it adds, saying there is ‘‘ medium confidence’ ’ in such findings .
Roshanka Ranasinghe was one of two Australians who worked as coordinating lead authors on the report, helped identify 33 so-called climate impact drivers (CIDs) and handled the Australasian assessment . He said 26 of the highlighted impacts were broadly relevant for Australia.
‘‘ Of these 26, we have high confidence that 11 CIDs will change in all four Australian regions by midcentury under all [emissions] scenarios but the lowest ones,’’ Professor Ranasinghe, chair in climate change impacts and coastal risk at IHE Delft/University of Twente, told The Age.
‘‘ This is consistent with the global warming level of about 2 degrees, relative to 1850-1900 .’’
These top 11 impacts included rising temperatures, extreme heat, ocean acidification and sea level rise, which were likely to get worse, while cold spells and frosts would decrease. ‘‘ We also have high confidence that snow will decrease by midcentury ,’’ he said.
Worsening bushfire weather, worsening marine heatwaves that spell danger for coral reefs, and lower winter rainfall for southern Australia are among the challenges to come. The broader report presents a picture of the current state of the world’s climate and lays out five potential scenarios for future emissions pathways.
More detail will be coming in the next two IPCC instalments.
However, regardless of what action the world takes now, warming over the coming decades is locked in due to the amount of greenhouse gas emissions already in the atmosphere and the lagging effect they have on the climate, said one of the report’s lead authors, CSIRO’s Pep Canadell.
If the world immediately makes drastic cuts to emissions, and reaches net zero or carbon neutrality before 2050, it can still stabilise the climate and see it slowly start to cool by the end of the century.
That would require curbing emissions to about 500 billion tonnes in total, or about 12 years of current pollution levels, and even then there would be only a 50-50 chance of limiting warming to 1.5 degrees compared with pre-industrial times.
‘‘ It is not too late,’’ said Dr Canadell. ‘‘ We are still in the control cabin of the planet and the climate system in determining the longterm future of climate.’’
He said climate change was already part of the personal experience of people enduring a wave of floods , heatwaves and fires , as seen recently in China, Canada and Greece and in Australia in the past two months.
‘‘ Every decimal of a degree [of warming] that we are avoiding is a win for us and a win for the climate,’’ he said.
The report says many of the impacts , particularly changes in ocean warming and acidification , sea levels and ice sheets, are locked in for hundreds if not thousands of years unless massive extractions of atmospheric carbon dioxide take place.
As well as likely scenarios, the report details climate changes that have a relatively low likelihood of occurring but could have devastating impacts, such as the sudden disintegration of ice sheets or mass forest die-back , which it says cannot be ruled out this century.
The report, formally titled Climate Change 2021: The Physical Science Basis, is the work of 234 scientists overseen by 195 governments and involves reviews of 14,000 scientific papers.
Since the first IPCC assessment report was completed in 1990, humans have emitted 1 trillion tonnes of carbon dioxide through burning fossil fuels or land clearing – about 41 per cent of all that emitted since the industrial revolution. The report has a greater focus than previous assessments on noncarbon dioxide greenhouse gasses such as methane, which it identifies as a significant contributor to warming . This could lead to increased pressure on Australia due to the government’s support of a gas-led recovery and significant agricultural methane emissions.
The federal government said climate change demanded a coordinated global response.
‘‘ The government is seeking to achieve net zero emissions as soon as possible,’’ Prime Minister Scott Morrison said in Parliament yesterday . ‘‘ We’re seeking to do that by using technologies, not taxes.’’
Labor climate change and energy spokesman Chris Bowen said the ‘‘ bare minimum’ ’ response from the federal government must be to set a deadline to reach net zero.
Greens leader Adam Bandt said a failure to lift Australia’s current goal of cutting greenhouse gas emissions to between 26 per cent and 28 per cent of 2005 levels would be ‘‘ criminal negligence’’ . The Greens are calling for net zero to be reached in 2035, or ahead of the government’s ‘‘ preference’ ’ to reach that point in 2050, and for a 75 per cent reduction by 2030.