Without serious efforts to limit further warming, humanity may be on the brink of triggering planet-altering climate “tipping points” long ahead of schedule.
The climate crisis is bringing the world closer to various critical thresholds that if passed would lead to a cascade of irreversible changes to the ecosphere and impacts on society.
The timeline of when tipping points may be triggered has been inching up for years, but new research published this week in the journal Science suggests the world may have already passed a critical juncture with the current level of warming, now thought to be around 1.2° C (2.2° F) above preindustrial levels.
“These changes may lead to abrupt, irreversible, and dangerous impacts with serious implications for humanity,” the researchers wrote. “Even global warming of 1° C, a threshold that we already have passed, puts us at risk by triggering some tipping points.”
What are climate tipping points?
Warming temperatures are already starting to cause the destruction of coral reefs, thawing of high-latitude permafrost, and collapse of massive ice sheets. Each of these could lead to a spiraling and self-perpetuating cycle of more carbon released into the atmosphere, temperatures rising even faster, and more widespread loss of both human and animal life.
Previous studies estimated that these tipping points likely would not be breached until global temperatures reached somewhere between 1.5° C and 2° C, but the new research appears to pour cold water on that theory.
The international researchers behind the new study, led by David Armstrong McKay of the University of Exeter in the U.K., combed through previous evidence and studies to identify 16 potential tipping points that could have either global or regional repercussions if crossed, finding that the timeline on many has moved up.
Ahead of schedule
The researchers found that five tipping points once considered unlikely to be crossed before global temperatures hit 1.5° C could topple with current levels of warming.
Six will likely be passed after 1.5° C of warming, including the die-off of tropical coral reefs and the collapse of both the Greenland and West Antarctic ice sheets.
Crossing these tipping points would lead to severe, long-lasting effects on the Earth’s topography and societies. Collapses of the Greenland and West Antarctic ice sheets alone could lead to sea levels rising by at least 3.5 meters, more than 11 feet.
Should temperatures break past the 2° C mark—the upper limit of warming decided upon in the 2015 Paris Agreement—even more tipping points would begin to fall, including the dieback of the Amazon rain forest and the loss of most mountain glaciers.
Based on stated climate pledges and national goalposts, the world could be on track to level off warming at around the 2° C mark, according to a recent study. Based on current policies, however, the planet is likely to heat to somewhere between 2.5 and 3° C.
Such warming would lead to a larger number of climate tipping points falling, and the new research suggests some may already be locked in given the absence of more ambitious environmental policies.
“Currently the world is heading toward around 2° C to 3° C of global warming; at best, if all net-zero pledges and nationally determined contributions are implemented it could reach just below 2° C,” the authors wrote. “This would lower tipping point risks somewhat but would still be dangerous as it could trigger multiple climate tipping points.”
Sign up for the Fortune Features email list so you don’t miss our biggest features, exclusive interviews, and investigations.
