A new IPCC science assessment, coming before COP26 in November, called for immediate action and showed that this summer’s extremes are only a mild preview of the decades ahead.
By Bob Berwyn
August 9, 2021
Amidst a summer of fires, floods and heat waves, scientists on Monday delivered yet another reminder that burning more fossil fuels in the decades ahead will rapidly intensify the impacts of global warming. Only pulling the emergency brake right now on greenhouse gas emissions can stop the planet from heating to a dangerous level by the end of the century, the scientists’ report concluded.
The report, Climate Change 2021: the Physical Science Basis, is the first installment of the Intergovernmental Panel on Climate Change’s Sixth Assessment Report (AR6), which will be completed in 2022. It was approved Aug. 6 by 195 member governments of the IPCC.
The report, by the panel’s Working Group I, assesses the physical science of climate change. It found that global warming is worsening deadly extremes like droughts and tropical storms and that every part of the planet is affected. “We see this signal in all regions. No region is really spared from climate change,” said Sonia Seneviratne, a coordinating lead author of the report and a climate researcher at ETH Zürich, where she focuses on climate extremes. The report shows that “Immediate reductions of CO2 emissions would be needed to retain a chance to limit global warming close to the 2.7 degrees Fahrenheit of warming targeted by the Paris climate agreement,” she added.
Seneviratne said that it had become apparent as the scientists worked on the report that many parts of the world were vulnerable to compounded climate impacts, with “extremes of different types leading to more impacts when combined, such as the co-occurrence of heatwaves and droughts.”
Recent examples include the deadly heat wave in the Pacific Northwest that was followed by a surge of forest fires in drought-stressed, dying forests. The warmer the planet, the higher the chances of crop-killing extremes affecting different agricultural areas at the same time, she said.
The IPCC report found that, without human-caused warming, there was “a near zero probability” of some of the deadliest recent heat waves, as well as other extremes like flooding rain. “We do see we need action immediately if we want to limit warming to somewhere around 1.5 degrees Celsius,” Seneviratne added.
That global climate target, equivalent to 2.7 degrees Fahrenheit warming from pre-industrial levels, was set in 2015 as part of the Paris climate agreement, and was based on the last major climate assessment from the IPCC. The new report confirms that beyond that level of warming, parts of the climate system, like the meltdown of ice sheets that raise sea level, could spiral out of control.
IPCC vice-chairwoman Ko Barrett, a deputy administrator with the National Ocean and Atmospheric Administration, said the new report provides “unequivocal” confirmation that humans are warming the planet to a dangerous level, causing widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere in every region of the world and across the whole climate system.
It also reflects “major advances” in understanding how “climate change intensifies specific weather and climate events such as extreme heat waves and heavy rainfall events,” said IPCC Working Group I Co-Chairwoman Valérie Masson-Delmotte, a research director at the French Alternative Energies and Atomic Energy Commission.
New climate models, with more accurate data of critical climate systems like clouds, also helped make the most accurate projections to date of how the climate would respond if greenhouse gas emissions stopped. While there are still some big question marks about how much CO2 permafrost and forests will take up and release in the future, the report suggests that the climate could begin stabilizing 20 to 30 years after greenhouse gas concentrations level off.
There is also no longer any question that global warming is changing the planet’s water cycle, the report found, bringing more intense rainfalls and flooding, as well as more intense droughts in many regions. Farther north and south, in higher latitudes, precipitation is likely to increase, but expected to decline in many already dry subtropical zones.
Since 1990, the panel has released five major climate science assessments, about five to six years apart, with special reports focusing on specific subjects in between. Going into the global COP26 climate talks in Glasgow in November, the latest science assessment gives negotiators a robust scientific basis that can empower decision-makers to take critical action.
Steve Cornelius, a former climate negotiator with the United Kingdom government who is now the chief climate advisor for WWF, said the 2018 IPCC report, which focused on the consequences of planetary warming of more than 1.5 degrees Celsius, provided an example of how science can spur action.
“Policymakers take notice of reports from the IPCC,” Cornelius said. “We have a net zero (carbon dioxide emissions) target in the UK that came about as a direct response to the IPCC’s 2018 report. That came out, and the government asked the Committee on Climate Change to come up with a plan for net-zero.” That would not have happened without the report, he said.
But at a global level, the response to the IPCC reports has not measured up to the urgency of the situation, said Saleemul Huq, director of the International Center for Climate Change and Development in Dhaka, Bangladesh.
“Past IPCC reports have served as the basis for promises to tackle global warming,” he said “But the actions that have actually been taken in practice neither conform to what countries promised to do and are nowhere near where the science says we must be.” The new report, he said, shows “how bad things are getting and why the world needs to speed up actions in line with the scientific needs.”
Talk of Tipping Points
Stephan Singer, a senior climate advisor with Climate Action Network International who is based in Brussels, represented environmental and climate activist groups during recent IPCC meetings. ”It was refreshing to see the U.S. back in the caucus of civilized nations,” he said, as the scientists and government reviewers finalized the report.
He added that the participation by environmental groups helped ensure that the IPCC didn’t stray away from the 1.5C warming target.
“There was a fear that the 1.5 target might be dropped,” Singer said. “We wanted to make sure that it stays in there as an option. But it’s tough and challenging, and we’re losing time every day.”
Singer said the environmental groups wanted “to make sure the report makes clear the need for urgent action.”
“We need to do things now in order to have a chance to meet net-zero,” he said, “and that includes protecting and restoring natural carbon sinks, like forests. And people need to understand this is the only IPCC report coming out before COP26 and before the United Nations General Assembly so, the language must be really clear.”
“All scenarios investigated by the IPCC show that global warming will probably exceed 1.5 degrees Celsius in the next few decades,” Singer said, showing how close we are to dangerous thresholds.
“The IPCC is strongly talking about tipping points,” Singer said, “ We can’t rule out significant forest diebacks and ice sheets falling apart, or other things that can feed back and make the warming even worse. We’re playing Russian roulette with five bullets in the gun.”
Same Message, Fewer ‘Weasel Words’
Scott Denning, an atmospheric scientist at Colorado State University, said the new IPCC report essentially hammers home the same message as all its predecessors, dating back to 1990.
“Each report has less and less weasel words, but it’s still pretty much the same message,” he said. “Adding CO2 to the atmosphere warms up the world.”
One new element of this latest IPCC science assessment is a more regional breakdown of global warming impacts, and some of its conclusions are underlined by current conditions in the Western United States. Water supplies in the West are drying to a trickle after a 20-year drought, dangerous heat waves are lasting longer and thousands of square miles of forest have burned up in the past few years.