As the planet warms, the sea ice is melting and the loss of its white surface, which reflected more of the Sun’s rays than the darker ocean, is causing temperatures to rise further. Result: the pack ice melts even more.
This kind of vicious cycle, called by scientists a feedback loop, is a growing source of concern for climate experts.
Researchers published Friday in the journal One Earth the most complete list to date, according to them, of these self-reinforcing chain reactions.
And they are sounding the alarm: their effect on the planet could be underestimated by current climate models, the accuracy of which is nevertheless crucial for guiding political decision-making, particularly in terms of greenhouse gas reduction. .
The researchers therefore call for a “huge international mobilization” of the scientific community to better assess the impact of these feedback loops. In particular, they are calling for an additional report from the IPCC, the UN’s group of climate experts, dedicated to this problem.
They also call for “immediate and colossal” climate action to reduce greenhouse gas emissions, in the face of the “potential major threat” posed by these feedback loops.
Some of them are indeed associated with what scientists call climatic “tipping points”, such as the collapse of the Greenland or Antarctic ice caps, which would cause a catastrophic rise in sea levels.
” Frightening “
To better understand what a feedback loop is, Christopher Wolf, co-author of the study, draws a comparison: during a bank run, customers withdraw their money en masse, for fear that their bank will collapse. . But this behavior only increases the risk of bankruptcy, pushing even more people to go to the counters – and so on.
In total, the researchers counted 41 climate feedback loops: 27 positive, that is to say reinforcing global warming, seven negative, and seven with an effect that is still uncertain.
Some are “frightening,” said William Ripple, also a co-author of the study. Like the thawing of the permafrost in the Arctic, which releases into the atmosphere greenhouse gases hitherto trapped in the ice, in particular methane. These gases thus fuel increased warming, and therefore the continuation of the thaw.
Similarly, fires, which are increasing due to climate change, release CO2 exacerbating the rise in temperature.
To establish this list, the researchers reviewed all the scientific literature on the subject.
Some feedback loops have been discovered recently, and others may be discovered in the near future, the study notes.
Their intensity can vary over time, and if some can act over the very long term, they can also one day or another come to an end (permafrost completely thawed, sea ice completely disappeared).
“If we can get a much better understanding of feedback loops and make the necessary changes […] we may still have time to limit the damage,” the study explains.
“Conversely, if the worst risks posed by feedback loops and tipping points have been underestimated, the future of a habitable planet could be at stake.”