‘Golden book’ of climate science to raise pressure for emissions action

Saudi Arabia and India are the nations making the most interventions during the final days of negotiations among the world’s top climate scientists as they finalise the latest assessment of how much the world is heating up.

The International Panel on Climate Change, a UN-backed body, is scheduled to release the first instalment of its Sixth Assessment Report – dealing with the physical sciences – on Monday evening AEST.

Buildings burn as the Dixie Fire this week tore through the Greenville community of Plumas County, California. The compounding events of weather extremes in a warming world will be part of the upcoming IPCC report.Credit:AP

Working Group I, as it is known, which has 234 scientific authors and more than 1000 contributors, is working around the clock to complete the IPCC’s first big update since 2013.

“The IPCC is really the golden book of climate sciences and how human activities are impacting [the planet],” said Pep Canadell, a co-ordinating lead author of the report and a senior CSIRO researcher.

As the scientists have been selected by 195 nations, including Australia, “governments are fundamentally owning the assessments”, Dr Canadell told a briefing by Australia’s Climate Council this week.

“A few years after one of these major reports, some major negotiation or political event has happened.”

This year, the IPCC report will help inform the upcoming climate summit planned for November in the Scottish city of Glasgow. Nations attending will be pressed to lift their carbon emission reduction efforts in order to meet the Paris Agreement of keeping warming to well below 2 degrees.

“There is a lot of interest to limiting the warming to 1.5 degrees [the lower end of the Paris target],” Dr Canadell said.

“There’s much more information that we didn’t have in the previous assessment, and that is really now at the core of the urgency and the commitments that many countries are now doing.”

Scientists involved in the process say the 30-plus page Summary for Policymakers is a painstaking affair, with each line coming under close scrutiny for accuracy and clarity.

Brad McCutcheon, a resident of St George Caravan Park, surveys the scene during flooding of the Hawkesbury River near Sydney in March 2021.Credit:Nick Moir

Saudi Arabia, the world’s largest oil exporter, is said to be the handbrake. “They are challenging every line,” said one participant who was not authorised to speak publicly.

India was providing the second-most interventions especially over placing the emphasis on historic emissions rather than future ones, as the Asian giant’s economy expands.

China was “relatively quiet” with its “major guns” absent, while Australia has been largely silent, the participant said.

Among the sticking points is when 1.5 degrees will be passed, and whether it is “crossed and lost”, with little chance of lowering temperatures back below that mark.

Of the three main Sixth Assessment reports, the physical science one typically has fewer changes than the other two, which deal with impacts and efforts to mitigate or halt climate heating.

Since the Fifth Assessment report, for instance, the IPCC has also released major studies of the science concerning melting ice and sea level rise, and whether temperature increases can be kept to 1.5 degrees. Warming since pre-industrial times is already at about 1.1 degrees.

The report is expected to say the timing of when 1.5 degrees will be crossed is likely to be sooner than previously forecast. In the IPCC’s 1.5 degree report, scientists concluded that “global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate”.

Steven Sherwood, a climate scientist at the University of NSW, and an author of previous Working Group I reports, said the report would probably provide an estimate of what greenhouse gas emission caps are needed to keep the temperature rise under 1.5 degrees, and the likelihood that it could be achieved.

“If we wait a few years [before acting], the answer will be ‘no’,” he said.

Discussion about how close earth systems are to reaching so-called tipping points, such as the destabilisation and stalling of the Gulf Stream or ice sheet disintegration, will also be examined closely.

Also of interest will be the scientists’ updated views on how extreme weather events, such as droughts and heatwaves, can have compounding effects, such as worsening bushfires.

Greater resolution of models will also provide pointers to how different regions will be affected. An interactive map is likely to show how the climate of Australia’s north, south, east and west will most likely alter in the future.

“For the first time, there’s an entire chapter on attribution science that was very, very poorly understood seven years ago [in the previous assessment reports],” Dr Canadell said.

“We’re now able to say more about why some of these extremes are happening, and to what extent, [there’s] the influence of humans.“

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