November 2020. In the paper, published as a commentary in the journal Nature this month, the group of researchers summarize the latest findings related to the threat of tipping points as part of effort to “identify knowledge gaps” and suggest ways to fill them. “We explore the effects of such large-scale changes,” the scientists explain, “how quickly they might unfold and whether we still have any control over them.”
Critics countered that the water vapor, methane vs. CO2 released from melting permafrost and albedo effects are too strong in the model used.
Permafrost creates the appearance of a grid in the National Petroleum Reserve-Alaska. David Houseknecht/U.S. Geological Survey
Nov. 2020
While the Intergovernmental Panel on Climate Change (IPCC) introduced the idea of tipping points two decades ago, the paper notes, it was long believed that what climatologists refer to as “large-scale discontinuities” in the planet’s natural system were “considered likely only if global warming exceeded 5°C above pre-industrial levels.” According to the researchers, however, more recent information and data—including the most recent IPCC summaries—suggest these frightening “tipping points could be exceeded even between 1 and 2 °C of warming”—that means this century, possibly within just decades.
Citing an “existential threat to civilization,” a group of top climate scientists have put out a new paper warning that the latest evidence related to climate tipping points—when natural systems reach their breaking point and cascading feedback loops accelerate collapse—could mean such dynamics are “more likely than was thought” and could come sooner as well.
In the paper, published as a commentary in the journal Nature on Wednesday, the group of researchers summarize the latest findings related to the threat of tipping points as part of effort to “identify knowledge gaps” and suggest ways to fill them. “We explore the effects of such large-scale changes,” the scientists explain, “how quickly they might unfold and whether we still have any control over them.”
“We’ll reach 1.5°C in one or two decades, and with three decades to decarbonize it’s clearly an emergency situation.” —Owen Gaffney, Stockholm Resilience Center
While the Intergovernmental Panel on Climate Change (IPCC) introduced the idea of tipping points two decades ago, the paper notes, it was long believed that what climatologists refer to as “large-scale discontinuities” in the planet’s natural system were “considered likely only if global warming exceeded 5°C above pre-industrial levels.” According to the researchers, however, more recent information and data—including the most recent IPCC summaries—suggest these frightening “tipping points could be exceeded even between 1 and 2 °C of warming”—that means this century, possibly within just decades.
“I don’t think people realize how little time we have left,” Owen Gaffney, a global sustainability analyst at the Stockholm Resilience Center at Stockholm University and a co-author of the paper, told National Geographic. “We’ll reach 1.5°C in one or two decades, and with three decades to decarbonize it’s clearly an emergency situation.”
Gaffney added, “Without emergency action our children are likely to inherit a dangerously destabilized planet.”
According to the paper:
If current national pledges to reduce greenhouse-gas emissions are implemented—and that’s a big ‘if’—they are likely to result in at least 3°C of global warming. This is despite the goal of the 2015 Paris agreement to limit warming to well below 2°C. Some economists, assuming that climate tipping points are of very low probability (even if they would be catastrophic), have suggested that 3°C warming is optimal from a cost–benefit perspective. However, if tipping points are looking more likely, then the ‘optimal policy’ recommendation of simple cost–benefit climate-economy models 4 aligns with those of the recent IPCC report 2. In other words, warming must be limited to 1.5 °C. This requires an emergency response.
Among the key evidence that tipping points are underway, the paper highlights a litany of global hot spots where runaway warming could unleash—or is already unleashing—dangerous feedback loops. They include: frequent droughts in the Amazon rainforest; Artic sea ice reductions; slowdown in Atlantic Ocean currents; fires and pests in the northern Boreal forest; large scale coral reef die-offs; ice sheet loss in Greenland; permafrost thawing in Eastern Russia; and accelerating melting in both the West and East Antarctic.
In an interview with the Guardian, Professor Tim Lenton at the University of Exeter, the lead author of the article, said: “As a scientist, I just want to tell it how it is. It is not trying to be alarmist, but trying to treat the whole climate change problem as a risk management problem. It is what I consider the common sense way.”
“This article is not meant to be a counsel of despair. If we want to avoid the worst of these bad climate tipping points, we need to activate some positive social and economic tipping points [such as renewable energy] towards what should ultimately be a happier, flourishing, sustainable future for the generations to come.” —Prof. Tim Lenton, University of Exeter
Citing campaigners around the world, including young people this year who kicked off global climate strikes, Lenton acknowledge that these people understand what world leaders seem unwilling to accept or act upon. “We might already have crossed the threshold for a cascade of interrelated tipping points,” Lenton said. “The simple version is the schoolkids are right: we are seeing potentially irreversible changes in the climate system under way, or very close.”
In their paper, the scientists write that “the consideration of tipping points helps to define that we are in a climate emergency and strengthens this year’s chorus of calls for urgent climate action—from schoolchildren to scientists, cities and countries.”
Despite the frightening warnings and the scale of the threat, the researchers are not trying to be doom-and-gloomers who say that nothing can be done.
In his comments to the Guardian, Lenton said, “This article is not meant to be a counsel of despair. If we want to avoid the worst of these bad climate tipping points, we need to activate some positive social and economic tipping points [such as renewable energy] towards what should ultimately be a happier, flourishing, sustainable future for the generations to come.”
But the paper makes clear that the climate emergency is here in very profound ways.
“In our view, the evidence from tipping points alone suggests that we are in a state of planetary emergency: both the risk and urgency of the situation are acute,” the paper states. The researchers even provide a mathematical risk equation:
The group of scientists also acknowledge that some in the scientific community believe their warnings exceed what the available evidence shows when it comes to the threat of tipping points or the timeline:
Some scientists counter that the possibility of global tipping remains highly speculative. It is our position that, given its huge impact and irreversible nature, any serious risk assessment must consider the evidence, however limited our understanding might still be. To err on the side of danger is not a responsible option.
If damaging tipping cascades can occur and a global tipping point cannot be ruled out, then this is an existential threat to civilization. No amount of economic cost–benefit analysis is going to help us. We need to change our approach to the climate problem.
The Guardian spoke to Professor Martin Siegert at Imperial College London, about the researchers’ paper and whether or not its warning comes in too heavy. “The new work is valuable,” Siegert said. “They are being a little speculative, but maybe you need to be.”
In the end, the new paper’s conclusion was twofold: more needs to be known about these crucial tipping points and that only urgent action can stave off the urgent threat an increasingly hotter world.
“We argue that the intervention time left to prevent tipping could already have shrunk towards zero, whereas the reaction time to achieve net zero emissions is 30 years at best,” the paper states. “Hence we might already have lost control of whether tipping happens. A saving grace is that the rate at which damage accumulates from tipping—and hence the risk posed—could still be under our control to some extent. ”
“The stability and resilience of our planet is in peril,” it concludes. “International action—not just words—must reflect this.”
**
Yes, there’s still hope to prevent catastrophic global warming. And yes, reducing greenhouse gas emissions to zero could still halt climate change, they said.
Doomsday climate study debunked by researchers, Chelsea Harvey, E&E News reporter, November 20, 2020
No, we haven’t reached a climate “point of no return.” That’s the overwhelming message from climate scientists in response to an alarming climate study that many experts described as flawed when it splashed across social media last week.
Yes, there’s still hope to prevent catastrophic global warming. And yes, reducing greenhouse gas emissions to zero could still halt climate change, they said.
Published in the journal Scientific Reports, the paper suggests the world has crossed an irreversible climate threshold. Even if all greenhouse gas emissions were stopped tomorrow, it concludes, the world would continue warming for hundreds of years. Indeed, the authors said that emissions would have had to stop in the 1960s to prevent runaway warming.
The paper suggests that a complicated series of feedback cycles led to unstoppable warming. Arctic ice melts away, allowing the Earth to absorb more heat. Rising temperatures cause the atmosphere to hold more water. Permafrost rapidly thaws, pouring carbon dioxide and methane into the air in the process. These extra carbon emissions drive even more warming.
It’s a striking scenario, to say the least. And it spawned a number of dire headlines last week, warning that the Earth had passed a point of no return.
But scientists say the paper has some serious problems.
Over the past week, numerous climate scientists have publicly criticized the paper. Most of their objections center on the model the study is based on.
The paper relies on simulations from a single Earth system model — and a simple one at that. The model is not among the suite of climate and Earth system models typically used by climate scientists in these kinds of studies. Rather, the model was designed by the study’s authors, Jørgen Randers and Ulrich Golüke, two business school professors in Norway.
Because the model is so simple, it relies heavily on built-in assumptions about the Earth and its climate system. And some of those key assumptions seem to conflict with what more advanced Earth system models typically suggest about the planet.
The way water vapor is held in the air as the Earth warms, for instance, is “at odds” with what other models tend to simulate, according to Zeke Hausfather, director of climate and energy at the Breakthrough Institute in Oakland, Calif.
The amount of warming it projects in response to rising methane emissions is probably too strong, as well. “There’s also some criticism of the permafrost assumptions they make and how much emissions come from that,” Hausfather said.
For instance, the simulations assume that permafrost thaws rapidly and that all the carbon it releases comes out in the form of methane, a significantly more potent greenhouse gas than carbon dioxide.
Merritt Turetsky, a permafrost expert at the University of Colorado, Boulder, pointed E&E News to a Twitter thread she posted in response to the study.
Permafrost is likely to thaw gradually in the future, she noted. And its emissions will include both carbon dioxide and methane, mostly CO2. The amount of methane assumed in this paper is “silly,” Turetsky tweeted. Furthermore, she added, some of the emissions from permafrost will likely be offset by Arctic plants that reabsorb some of that carbon.
None of this is to say that permafrost isn’t worth keeping a close eye on. Many scientists agree that thawing permafrost is a major uncertainty in projections about future climate change — scientists are still working to understand how quickly permafrost is likely to thaw as the planet warms and how much carbon it will emit.
That said, permafrost is represented “very crudely” in a lot of models, Turetsky noted. So there’s definitely room to keep improving its place in climate simulations.
But experts generally agree that the simple model used in the study last week produced unrealistic assumptions. That’s good news. It means the doomsday portrait it paints is probably bunk.
Richard Betts, a climate scientist at the University of Exeter, noted that the paper relies on a model with “major flaws” and suggested that its assumptions about water vapor and the effects of melting snow and ice on the climate are likely too strong.
Reto Knutti, a climate scientist at ETH Zurich, affirmed that the model’s assumptions about permafrost are inconsistent with more complex models and noted that other studies find that reducing greenhouse gases to zero stops global warming.
Daniel Swain, a climate scientist at UCLA, also pointed out that the study’s title contains an error — it refers to “melting” permafrost, when the accepted scientific term is “thawing.”
Following the backlash, Scientific Reports amended a press release it had previously published about the study. “The authors encourage other researchers to explore their results using alternative models,” it said.
Since the initial wave of doomsday headlines last week, the strong response from scientists has also been reported by various outlets.
There are real risks that come with amplifying an unrealistically grim climate future, Hausfather noted.
“There’s a really pernicious idea that sort of rears its head every now and then, that it’s sort of too late — we’re past the point of no return; we’re locked into some sort of runaway climate change no matter what we do,” he said. “That’s generally not supported by the science in any way, shape or form.”
This kind of messaging can imply that climate action is futile and that nothing can be done to avert the coming disaster, Hausfather warned. That’s false.
Climate change remains an existential threat to the planet, and continued warming will only worsen the consequences already playing out across the planet — rising sea levels, thawing ice, intensifying heat waves and more extreme weather events, to name a few. But research consistently indicates that curbing greenhouse gas emissions could stop global warming.
“Anything like this, that is not representative of the consensus on these matters and gives ammunition to the doomist crowd, is problematic,” Hausfather said.Twitter: @chelseaeharveyEmail: charvey@eenews.net
