These Climate Change Tipping Points May Have Already Been Reached: 'We Now Pose a Threat to Our Current Civilization'

World leaders must take urgent action to tackle climate change, say scientists who warn "abrupt" and "irreversible" climate tipping points that threaten human civilization may have already started.

In a startling article published in the journal Nature offering a glimmer of hope, scientists highlighted tipping points— which are likely interconnected—that if met could create a domino-effect of "long-term irreversible changes" to the planet.

"Evidence that tipping points are underway has mounted in the past decade," the experts wrote.

If we reach a stage where tipping points can't be ruled out, "this is an existential threat to civilization," they warned. "No amount of economic cost-benefit analysis is going to help us. We need to change our approach to the climate problem."

Tipping points are thresholds that, once passed, can trigger rapid changes to climate systems. These were first described by the United Nations Intergovernmental Panel on Climate Change (IPCC) two decades ago. At that time it was thought they would likely happen if global warming exceeded pre-industrial levels by 5 C. But since then, new research has indicated the events could happen even with 1 C to 2 C of warming, the scientists said.

"Abrupt and irreversible changes in the climate system have become a higher risk at lower global average temperatures," they warned.

Referring to the parts of the Earth covered in ice, the scientists said: "Several cryosphere tipping points are dangerously close, but mitigating greenhouse-gas emissions could still slow down the inevitable accumulation of impacts and help us to adapt."

Evidence suggests the Amundsen Sea embayment of West Antarctica may have already hit a tipping point, as the point where the ice, ocean and bedrock meet is "retreating irreversibly," experts wrote.

If this area collapses, the remaining West Antarctic ice sheets could be destabilized, "leading to about 3 meters [9.8 feet] of sea-level rise on a timescale of centuries to millennia," according to a prediction cited by the authors. The Wilkes Basin on the East Antarctic could face a similar fate, and the Greenland ice sheet could be "doomed" at 1.5 C of warming as soon as 2030.

"We might already have committed future generations to living with sea-level rises of around 10 meters over thousands of years," the scientists wrote.

More research is needed to confirm whether ice sheets are heading towards tipping points. But action must be taken to slow sea-level rises for us to adapt to climate change regardless, they said.

Elsewhere, ocean heatwaves have caused mass coral bleaching, and the loss of half of shallow-water coral on the Great Barrier Reef in Australia. If average global temperatures spike by 2 C, 99 percent of tropical coral could be lost. "This would represent a profound loss of marine biodiversity and human livelihoods," the scientists wrote.

Meanwhile, 17 percent of the Amazon rainforest has disappeared since 1970. Scientists think a tipping point for the world's biggest forest could lie between 20 to 40 percent loss of cover.

Global warming has also affected North America's boreal forests, which could turn "some regions from a carbon sink to a carbon source," and started the irreversible process of thawing permafrost, which releases harmful greenhouse gasses. All this could erase our remaining emissions budget if we have a chance of staying within the 1.5 C warming target, the scientists warned,

"In our view, the clearest emergency would be if we were approaching a global cascade of tipping points that led to a new, less habitable, 'hothouse' climate state," the scientists said on the potential domino effect.

"Warming must be limited to 1.5 C. This requires an emergency response," they stressed. But if current national pledges to cut greenhouse-gas emissions are met, the average rise in global temperatures will still hit 3 C.

The article comes at the end of a year marked by an explosion of concern in climate change, which has prompted children to join school strikes lead by teenage activist Greta Thunberg.

Co-author Professor Tim Lenton, director of the Global Systems Institute at the U.K.'s University of Exeter, told Newsweek: "I think we now pose a threat to our current civilzation, if we let global warming continue unchecked."

"The planet will transition into a different state, possibly with some other life forms coming to dominate, or possibly with some surviving humans creating a different civilization. But no one reading this should want that outcome," he said.

Lenton and colleagues chose to write the article now "because we are facing a climate emergency but we are not acting collectively as if we were in an emergency situation."

"10 years ago my colleagues and I identified a suite of potential tipping points in the climate system," he explained. "In the last decade new evidence has shown that several of these tipping points are much closer than we thought, and some appear to have been passed in Antarctica committing future generations to significant, irreversible sea-level rise."

To avoid the tipping points, Lenton said politicians and policymakers worldwide must stop heavily subsidizing the extraction of fossil fuels, and instead increase their investment in sustainable energy sources, sustainable transport, and the associated infrastructure.

Most countries have committed to the Paris Agreement, but their actions need to match their rhetoric, urged Lenton.

Addressing the U.S., Lenton said many cities—including New York City, San Francisco, Washington and Los Angeles—and some states are showing valuable leadership on climate change but that "the U.S. as a whole is not doing anything like enough."

Earlier this month, the U.S. State Department announced it would start the formal process of withdrawing from the agreement, following an announcement by President Donald Trump in June 2017. Former President Barack Obama had previously committed to cutting emissions by 26 to 28 percent by 2025.

The U.S. "could be leading the world towards a flourishing, sustainable future—clearly having a President that doesn't take the issue seriously doesn't help, but it goes back before this presidency," according to Lenton, who said the country has a huge amount to gain from trying to solve climate change.

Lenton argued the Green New Deal is "a really positive step," and the same logic applies for other regions, such as Europe.

He also suggested far-right populist Brazilian president Jair Bolsonaro should receive global financial help to "stop incentivizing Amazon rainforest destruction and instead penalize those doing it."

At the same time, the public can help by changing diets, taking fewer long-haul flights and insulating their homes, said Lenton.

"We now need a positive social tipping point to avoid the worst climate tipping points," he said.

Lenton said we can avoid catastrophe "if we work hard to limit global warming below 2 C and reduce other pressures on our life-support system. In the process we would also be creating long-term, sustainable flourishing for our species. So this crisis is also an opportunity."

"But we cannot afford to wait for [more] bad [climate] stuff to happen because then it will be too late. We need to listen to the warning signals from climate tipping points and act now," he said.

Fridays For Future, climate change, global warming,berlin
Participants in the Fridays For Future movement protest during a nationwide climate change action day on September 20, 2019 in Berlin, Germany. Maja Hitij/Getty