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"It is clear that we are currently on a dangerous trajectory," said one University of Exeter professor.
Scientists on Wednesday released yet another study warning that humankind is at risk of triggering various climate "tipping points" absent urgent action to dramatically reduce planet-heating emissions from fossil fuels.
The new peer-reviewed paper, published Wednesday in the journal Earth System Dynamics, comes from a trio of experts at the United Kingdom's University of Exeter and the University of Hamburg in Germany.
Climate scholars use the term "tipping point" to describe a critical threshold which, when crossed, "leads to significant and long-term changes of the system," the paper notes. Debate over it "has intensified over the past two decades," prompting several studies of specific risks.
"Climate tipping points could have devastating consequences for humanity," said co-author Tim Lenton in a statement. "It is clear that we are currently on a dangerous trajectory—with tipping points likely to be triggered unless we change course rapidly."
"We need urgent global action—including the triggering of 'positive tipping points' in our societies and economies—to reach a safe and sustainable future," added the Exeter professor and Global Systems Institute director.
Lenton's team calculated the probabilities of triggering 16 tipping points. They looked at the risks of serious damage to key glaciers, ice sheets, sea ice, and permafrost; the dieback of forests such as the Amazon; the die-off of low-latitute coral reefs; and the collapse of the Atlantic Meridional Overturning Circulation (AMOC), which is part of a crucial "global conveyor belt" of ocean currents.
To assess the risk of current policies triggering climate tipping points, the researchers focused on a scenario in which median warming of 2.8°C takes place by the end of the century.
On that pathway, the study says, "our most conservative estimate of triggering probabilities averaged over all tipping points is 62%... and nine tipping points have a more than 50% probability of getting triggered."
Under scenarios with lower temperature rise, "the risk of triggering climate tipping points is reduced significantly," the study continues. "However, it also remains less constrained since the behaviour of climate tipping points in the case of a temperature overshoot is still highly uncertain."
The paper concludes that "rapid action is needed to reduce greenhouse gas emissions, since climate tipping points are already close, and it will be decided within the coming decades if they will be crossed or not."
Lead author Jakob Deutloff shared that takeaway a bit more optimistically, saying that "the good news from our study is that the power to prevent climate tipping points is still in our hands."
"By moving towards a more sustainable future with lower emissions, the risk of triggering these tipping points is significantly reduced," he added. "And it appears that breaching tipping points within the Amazon and the permafrost region should not necessarily trigger others."
▶️New paper from Jakob Deutloff, Hermann Held and Tim Lenton highlights the need for action to prevent triggering climate tipping points. More on this at The Global Tipping Points conference @exeter.ac.uk Register now! global-tipping-points.org/conference-2... esd.copernicus.org/articles/16/...
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— Global Systems Institute (@gsiexeter.bsky.social) April 23, 2025 at 4:45 AM
The paper was published during Covering Climate Now's joint week of media coverage drawing attention to the 89% of people worldwide who want their governments to do more to address the global crisis; ahead of a Global Systems Institute conference on tipping points this summer; and just over six months away from the next United Nations climate summit, COP30, in Brazil.
While some governments are trying to prevent the worst-case scenario by taking action to cut emissions, U.S. President Donald Trump has made clear since returning to office in January that he aims to deliver on his pro-fossil fuel campaign pledge to "drill, baby, drill."
On the heels of the
hottest year in human history, Trump is working to gut key agencies, ditched the Paris climate agreement, and has taken executive action to boost planet-wrecking coal, gas, and oil, including declaring a national energy emergency.
The study was published as President Donald Trump was blasted for an executive order that one critic said shows he wants to turn the Alaskan Arctic into the "the world's largest gas station."
For thousands of years, the land areas of the Arctic have served as a "carbon sink," storing potential carbon emissions in the permafrost. But according to a study published in the journal Nature Climate Change Tuesday, more than 34% of the Arctic is now a source of carbon to the atmosphere, as permafrost melts and the Arctic becomes greener.
"When emissions from fire were added, the percentage grew to 40%," according to the Woodwell Climate Research Center, which led the international team that conducted the research.
The study, which was first reported on by The Guardian, was released the day after President Donald Trump issued multiple presidential actions influencing the United States' ability to confront the climate crisis, which is primarily caused by fossil fuel emissions, including one directly impacting resource extraction in Alaska, a section of which is within the Arctic Circle.
Sue Natali, one of the researchers who worked on the study published in Nature Climate Change, toldNPR in December (in reference to similar research) that the Arctic's warming "is not an issue of what party you support."
"This is something that impacts everyone," she said.
As the permafrost—ground that remains frozen for two or more years—holds less carbon, it releases CO2 into the atmosphere that could "considerably exacerbate climate change," according to the study.
"There is a load of carbon in the Arctic soils. It's close to half of the Earth's soil carbon pool. That's much more than there is in the atmosphere. There's a huge potential reservoir that should ideally stay in the ground," said Anna Virkkala, the lead author of the study, in an interview with The Guardian.
The dire warning was released on the heels of Trump's executive order titled "Unleashing the Alaska's Extraordinary Resource Potential" that calls for expedited "permitting and leasing of energy and natural resource projects in Alaska," as well as for the prioritization of "development of Alaska's liquefied natural gas (LNG) potential, including the sale and transportation of Alaskan LNG to other regions of the United States and allied nations within the Pacific region."
The order also rolls back a number of Biden-era restrictions on drilling and extraction in Alaska, which included protecting areas within the Arctic National Wildlife Refuge from oil and gas leasing.
"Alaska is warming four times faster than the rest of the planet, a trend that is wreaking havoc on communities, ecosystems, fish, wildlife, and ways of life that depend on healthy lands and waters," said Carole Holley, managing attorney for the Alaska Office of the environmental group Earthjustice, in a statement Monday.
"Earthjustice and its clients will not stand idly by while Trump once again forces a harmful industry-driven agenda on our state for political gain and the benefit of a wealthy few," she added.
Trump wants to turn the Alaskan Arctic into the "the world's largest gas station," said Athan Manuel, director of Sierra Club's Lands Protection Program, in a statement Monday. "Make no mistake, Trump's rushed and sloppy actions today are an existential threat to these lands and waters, and the communities and wildlife that depend on them."
"Only by doing much more in this critical decade to bring emissions down and peak temperatures as low as possible, can we effectively limit damages."
Just over a month away from the next United Nations climate summit, a study out Wednesday warns that heating the planet beyond a key temperature threshold of the Paris agreement—even temporarily—could cause "irreversible impacts."
The 2015 agreement aims to limit global temperature rise this century to 1.5ºC, relative to preindustrial levels.
"For years, scientists and world leaders have pinned their hopes for the future on a hazy promise—that, even if temperatures soar far above global targets, the planet can eventually be cooled back down," The Washington Postdetailed Wednesday. "This phenomenon, known as a temperature 'overshoot,' has been baked into most climate models and plans for the future."
"The earlier we can get to net-zero, the lower peak warming will be, and the smaller the risks of irreversible impacts."
As lead author Carl-Friedrich Schleussner said in a statement, "This paper does away with any notion that overshoot would deliver a similar climate outcome to a future in which we had done more, earlier, to ensure to limit peak warming to 1.5°C."
"Only by doing much more in this critical decade to bring emissions down and peak temperatures as low as possible, can we effectively limit damages," stressed Schleussner, an expert from Climate Analytics and the International Institute of Applied Systems Analysis who partnered with 29 other scientists for the study.
The paper, published in the peer-reviewed journal Nature, states that "for a range of climate impacts, there is no expectation of immediate reversibility after an overshoot. This includes changes in the deep ocean, marine biogeochemistry and species abundance, land-based biomes, carbon stocks, and crop yields, but also biodiversity on land. An overshoot will also increase the probability of triggering potential Earth system tipping elements."
"Sea levels will continue to rise for centuries to millennia even if long-term temperatures decline," the study adds, projecting that every 100 years of overshoot could lead seas to rise nearly 16 inches by 2300, on top of more than 31 inches without overshoot.
The scientists found that "a similar pattern emerges" for the thawing of permafrost—ground that is frozen for two or more years—and northern peatland warming, which would lead to the release of planet-heating carbon dioxide and methane. They wrote that "the effect of permafrost and peatland emissions on 2300 temperatures increases by 0.02ºC per 100 years of overshoot."
"To hedge and protect against high-risk outcomes, we identify the geophysical need for a preventive carbon dioxide removal capacity of several hundred gigatonnes," the authors noted. "Yet, technical, economic, and sustainability considerations may limit the realization of carbon dioxide removal deployment at such scales. Therefore, we cannot be confident that temperature decline after overshoot is achievable within the timescales expected today. Only rapid near-term emission reductions are effective in reducing climate risks."
In other words, as co-author and Climate Analytics research analyst Gaurav Ganti, put it, "there's no way to rule out the need for large amounts of net negative emissions capabilities, so we really need to minimize our residual emissions."
"We cannot squander carbon dioxide removal on offsetting emissions we have the ability to avoid," Ganti added. "Our work reinforces the urgency of governments acting to reduce our emissions now, and not later down the line. The race to net-zero needs to be seen for what it is—a sprint."
While the paper comes ahead of COP29, the U.N. conference in Azerbaijan next month, co-author Joeri Rogelj looked toward COP30, for which governments that have signed the Paris agreement will present their updated nationally determined contributions (NDCs) to meet the climate deal's goals.
"Until we get to net-zero, warming will continue. The earlier we can get to net-zero, the lower peak warming will be, and the smaller the risks of irreversible impacts," said Rogelj, a professor and director of research for the Grantham Institute at Imperial College London. "This underscores the importance of countries submitting ambitious new reduction pledges, or so-called 'NDCs,' well ahead of next year's climate summit in Brazil."
The U.N. said last November that countries' current emissions plans would put the world on track for 2.9°C of warming by 2100, nearly double the Paris target. Since then, scientists have confirmed that 2023 was the hottest year in human history and warned that 2024 is expected to set a new record.
The study in Nature was published as Hurricane Milton—fueled by hot waters in the Gulf of Mexico—barreled toward Florida and just a day after another group of scientists wrote in BioScience that "we are on the brink of an irreversible climate disaster. This is a global emergency beyond any doubt. Much of the very fabric of life on Earth is imperiled."
Those experts emphasized that "human-caused carbon dioxide emissions and other greenhouse gases are the primary drivers of climate change. As of 2022, global fossil fuel combustion and industrial processes account for approximately 90% of these emissions, whereas land-use change, primarily deforestation, accounts for approximately 10%."