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 models4 aligns with those of the recent IPCC report2. 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."