Only by drastically reducing greenhouse gas emissions, while removing carbon dioxide from the atmosphere, can we stop the precipitous trend.
“At the end of the day, we have zero years left to avoid dangerous climate change, because it’s here,” Michael E. Mann, one of the lead authors of the 2001 IPCC report, told CNN.
Even in the IPCC’s most optimistic scenario, in which global emissions begin to decline sharply today and are reduced to net zero by 2050, global temperature will still peak above the 1.5 degree threshold before rising. fall.
In a statement, UN Secretary General António Guterres called the report a “red code for humanity” and noted that the 1.5 degree threshold is “dangerously close”.
“The only way to avoid going beyond this threshold is to urgently step up our efforts and pursue the more ambitious path,” said Guterres.
The IPCC report comes just three months ahead of the UN-led international climate change talks, in which world leaders are expected to step up commitments to cut greenhouse gas emissions.
Although some countries have promised tougher cuts since the 2015 Paris Agreement, many have missed the deadlines to do so, and there is still a significant gap between what leaders promise and what is needed. ‘by 2030.
“From a scientific point of view, every degree, every part of a diploma, every half of a degree counts in limiting the impacts that we will see from climate change,” Ko Barrett, former vice president of the United Nations, told CNN. IPCC. “So whatever level countries decide is what they are aiming for, there are advantages and there are consequences in choosing those limits.”
Dave Reay, director of the Edinburgh Climate Change Institute, said world leaders “must have the findings of this report engraved in their minds” at the November conference and take urgent action.
“It’s not just another scientific report,” Reay said. “It’s hell and high water basically.”
As computing power increases, scientists are more confident than ever to connect the dots between the climate crisis and extreme weather conditions, which for some regions – even at 1.1 degrees of warming – are already becoming unbearable.
Michael Byrne, a climate scientist at the University of Oxford, said what was different about this report is that “the effects of global warming are no longer in the distant future or in remote corners of the world.” .
“We knew what was coming and now it’s here,” Byrne said.
The IPCC says the heavy precipitation that used to occur once every 10 years now occurs 30% more frequently.
“We’re seeing some really scary fire behavior. I don’t know how to exaggerate that,” said Chris Carlton, supervisor supervisor of the Plumas National Forest in California, who called this year’s wildfire season a “wildfire season”. unexplored territory “.
Charles Koven, one of the lead authors of the report’s chapter on global carbon cycles, said California has already reached a tipping point on wildfires.
“I don’t think we knew where that threshold was until we crossed it,” he told CNN. “What the report makes clear is that the likelihood of crossing any of these tipping points is certainly going to increase the warming that we are seeing.”
With each fraction of a degree of warming, the effects worsen. Even limiting warming to 1.5 degrees, which the Paris Agreement countries have determined is ideal for avoiding the worst impacts, the types of extreme weather conditions the world has experienced this summer will become more severe and more severe. frequent.
Beyond 1.5 degrees, scientists say the climate system might start to look unrecognizable.
Andrew Watson, a scientist at the University of Exeter, said the climate models used in the report do not capture the risk of “low probability, high impact” events that become more likely as global temperatures rise. increased.
The approximately 3,500-page report is the culmination of nearly a decade of climate research by scientists around the world. And while the IPCC is seen as the ultimate source on climate change, it tends to be cautious in its conclusions because of the way it is developed – getting hundreds of scientists to reach consensus not only on research but on the language that describes it.
Yet Monday’s report uses the strongest wording yet to describe the climate crisis. Ice caps are melting and will continue to melt; extreme flooding due to sea level rise will continue to be more frequent; and the sea level itself will continue to rise until the 22nd century, simply because of the amount of heat the oceans have already trapped.
The IPCC report makes it clear that world leaders must reduce greenhouse gas emissions now, before deadly and costly extreme weather conditions escalate. But Barrett said a key message from the report is that the most serious impacts can always be prevented.
“It really requires unprecedented transformational change, a rapid and immediate reduction of greenhouse gas emissions to net zero by 2050,” Barrett said. “The idea that there is still a way forward is something that should give us some hope.”
CNN’s Angela Dewan, Brandon Miller and John Keefe contributed to this report.
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