Climate Change | Earth at the threshold of five tipping points

Review Science has just published the conclusions of a study according to which the planet is dangerously approaching five tipping points (tipping points) which will cause significant climatic disturbances… and risk creating a domino effect.

Andre Duchesne
The Press

In the Paris Accords window

The scientific consensus indicates that the current temperature is 1.1 degrees Celsius higher than in the pre-industrial era. The Paris Agreements aim to limit the increase in global warming to 1.5°C, with an upper limit of 2°C. However, the article of Science reveals that as soon as 1.5°C is reached, or before considering the margin of error, the planet could reach five tipping points of irreversible climatic upheavals. “Our assessment provides strong scientific evidence aimed at urgent action in hopes of mitigating these changes,” the scientific summary concludes.

The five closest points…

The five climatic disturbances likely to occur at a warming of 1.5 degrees are the melting of the Greenland ice sheet, the melting of the West Antarctic ice sheet, the death of tropical corals, the thawing of northern permafrost and the loss of sea ice in the Barents Sea. These changes will not be instantaneous. They will take place over a period of a few years to a few hundred years. For example, it is estimated that once started, permafrost thaw will last for an average period of 50 years and the melting of the Greenland ice cap will last for 10,000 years.

Ah! So it’s far!

Not at all ! It’s tomorrow ! “It’s very short on the biogeochemical scale,” says Jérôme Dupras, professor at the University of Quebec in Outaouais and holder of the Research Chair in Ecological Economics. “Take the disappearance of the dinosaurs. It is attributable to the fall of a meteorite which also upset the biodiversity of the Earth over two million years. However, the rise of 1.1 degrees Celsius since the pre-industrial era dates back approximately 150 years, and we have observed significant changes in climate. The rapidity of these changes is going at an astonishing speed. »

Nine more tipping points

The study of Science identifies a total of 16 tipping points, nine globally and seven regionally. In addition to the cases mentioned above, there is thus the melting of glaciers, the loss of the Amazonian forest, the collapse of the ocean current (AMOC) which plays a role of thermostat for the planet, the retreat towards the north of the boreal forest, the end of the (providential) monsoons in the Sahel and West Africa. These tipping points will not all occur at the same time. It is estimated, for example, that four of them will occur at 4°C of warming (with a margin of error). But there is nothing to be relieved about. “Ten years ago, it was estimated that these tipping points would occur in an Earth 3°C warmer,” recalls Jérôme Dupras. In 2019, a new study in Science estimated that nine tipping points are likely to be triggered at 1.5°C. And now this new study tells us that five of them are already committed to a 1.1°C planet. »

Domino effect

The triggering of tipping points is all the more worrying as they can have a domino effect. “Overall, we can get carried away,” says Dominique Gravel, professor in the biology department at the Université de Sherbrooke and holder of the Canada Research Chair in Integrative Ecology. “We trigger the first tipping point which increases the warming which triggers the second, the third and the others in cascade. The example of the melting permafrost is, in this regard, instructive and worrying. “If the permafrost starts to melt, it will release very large amounts of methane and CO₂ stored in the soil, says Mr. Gravel. And this feedback will be permanent, even if we become carbon neutral. The melting of permafrost will continue and will release new greenhouse gases (GHGs) into the atmosphere that will keep temperatures rising. »

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