At more than 1.5°C of warming, points of no return will be crossed!

Experts agree. Unless we succeed in dividing our emissions of greenhouse gas halving by 2030 and achieving net zero emissions by 2050, we will only have a 50% chance of meeting the 2015 goal set by the Paris Climate Agreement of limiting anthropogenic global warming to 1.5°C above pre-industrial temperatures.

A new study today confirms how damaging this could be. A study that some do not hesitate to call a study “the most important of all time”. A study devoted to points of no return.

Tipping points, should we probably rather say. According to the Intergovernmental Panel on Climate Change (IPCC), they correspond to “critical thresholds beyond which a system reorganizes, often brutally and/or irreversibly”. Understand that when crossed, these thresholds trigger large-scale and potentially irreversible upheavals for a particular region of our Earth system. L’analogy proposed by Carbon Brief is interesting. A tipping point is a bit like when you end up removing the wrong brick from a tower in Jenga. Everything is collapsing!

Tipping points scrutinized

In 2008, Tim Lenton, a researcher at the University of Exeter (UK), was the first to assess these tipping points. He is now part of the team providing an update to this assessment. An update based on a review of hundreds of scientific works. The conclusion is clear. ” The list of tipping points has lengthened and our assessment of the risk they pose has increased significantly”entrusts the researcher to the Guardian.

The new study indeed identifies a total of sixteen tipping elements. Nine that effectively affect the entire system earth and seven with deep regional consequences. In 2008, there were only nine points. And not necessarily the same. This update should therefore make it possible to refocus efforts. Especially since it also describes the temperature thresholds for each of the switching points. As well as their timescales and impacts.

Systems on the brink

Even more worrisome than a growing number of tipping points, the fact that researchers estimate that current global warming — about 1.1°C above pre-industrial averages — may have already driven our Planet beyond a climatic state ” sure “. The first tipping points may even have been crossed. Serious warning signals have been sent out from the side of the arctic ice capof the Amazon forest or the meridian overturning circulation of the Atlantic (Amoc). Many studies suggest that the western cap Antarctic is extremely close to its tipping point. If she hasn’t passed it already…

If we were to reach the famous 1.5°C of warming predicted by the Paris Agreement, four other tipping points would be ” most likely “ crossed and five more, “possibly”. The glaciers of our mountains would be threatened, as would the boreal forests. It would be much worse, you can imagine, if the current trajectory of a warming of around 2.5°C were maintained.

However, these works should not be taken for more than they are. Namely, a “good first step” in the assessment of tipping points. Because the uncertainties remain important and the forecasts of the climate models on this subject ultimately rather unreliable.

Another phenomenon also remains to be taken into account: the failover cascade. A kind ofdomino effect considered by researchers of a tipping point that could lead to others. And thus lower the thresholds of no return. What, once again, to encourage urgent action to limit our emissions of greenhouse gas.

Climate change: half of the tipping points reached faster than expected

In matter change, scientists define tipping points as thresholds which, once exceeded, lead to significant changes in our planet. And precisely, some of them would already be exceeded, raising fears of a cascade of dramatic consequences.

Article of Nathalie Mayer published on 28/11/2019

“A decade ago we identified a series of points of no return potential in the Earth system. Politicians, economists and even some scientists refused to believe that they could ever be reached. Yet today, we have proof that more than half of them have been exceeded. » This is the sad observation shared by researchers in the journal Nature. In question, you will have understood: the global warming caused by human activities.

As is the case for the greenhouse gas emissionsthem pressures are increasing and continuing to rise beyond already unprecedented levels. “But we must also recognize that we have underestimated the risks”, emphasizes Johan Rockström, director of the Institute for Climate Impact Research in Potsdam (Germany). Those of an Earth which finally seems to “self-amplify” its warming. And to define how much, researchers will still have to work hard.

In the past, experts thought that to endanger our planet, we would have to reach a temperature 5°C above pre-industrial averages. They have since reviewed their copy. They now estimate that a warming of 1 to 2°C would be enough to cause a cascade of disasters.

Urgently limit our emissions

However, the global temperature is already 1.1°C above pre-industrial averages. And it is likely that the Earth will cross the +1.5°C mark as early as 2030. There is, obviously, no more time to waste in declaring a emergency state planetary. Because, according to researchers, global warming now threatens the very existence of human civilizations.

Listing the effects of climate change that could already be irreversible, they mention the melting of the ice cap Antarctica and the disappearance of permafrost arctic that could cause a sea ​​level rise ten meters. The disappearance of large swaths of boreal forests and the Amazon rainforest, too, which leads to an additional release of CO₂ in the air. But also the bleaching of corals or the slowing down of Gulf Stream.

“It’s not about being alarmistnotes Tim Lenton, researcher at the University of Exeter (United Kingdom). Even if it is now necessary to act urgently and that perhaps THE point of no return has already been crossed, we still have the power to limit the risks incurred… by immediately reducing our emissions”.