Climate change: catastrophic consequences even at 1.5°C, says study

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Climate change: catastrophic consequences even at 1.5°C, says study

Many Inuit communities in northern Canada must adapt their practices to the new realities imposed by climate change. (Archives)

Global warming beyond 1.5°C, the most ambitious goal of the Paris Agreement, could trigger several Climate “tipping points” that would trigger catastrophic chain reactions, according to a study published Thursday in the journal Science.

And current temperatures, already rising, threaten to trigger five of these tipping points, including those for the Antarctic and Greenland ice sheets, warn the study authors, who believe however that it's not too late to act.

For me, it will change the face of the world, literally, if you watch from space, with rising sea levels or the destruction of forests, explained Tim Lenton, one of the lead authors of the study.

A barrier announces that the Dettah Ice Road, which passes over Great Slave Lake in the Northwest Territories, is closed.

He signed the first major publication on this subject in 2008.

A tipping point is a critical threshold beyond which a system reorganizes, often abruptly and/or irreversibly, as defined by the UN Panel of Climate Experts (IPCC). They are phenomena that independently and ineluctably trigger other cascading consequences.

If initial analyzes estimated their trigger threshold in a range of 3 to 5°C of warming, progress in observations and climate modeling, as well as in the reconstruction of past climates, have drastically lowered this assessment.

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The study published in Science is a synthesis of more than 200 scientific publications, conducted in order to better predict the thresholds for triggering these breakpoints.< /p>

The authors identify nine major tipping points at the planetary level and seven at the regional level, 16 in total.

Of these, five could be triggered by current temperatures, which have gained almost 1.2°C on average since the pre-industrial era: the one concerning the ice sheets in Antarctica and Greenland, a sudden thaw of the permafrost , the cessation of a heat transfer phenomenon in the Labrador Sea and the extinction of coral reefs.

With a warming at 1, 5°C, four more points move from possible to probable, and five more become possible, according to the study.

For the ice caps of West Antarctica and Greenland, crossing the breaking point estimated by scientists would contribute, over hundreds of years, to a rise in sea level of 10 meters, explains Tim Lenton , from the British University of Exeter.

This aerial photo taken in 2021 shows the collapse of a section of permafrost that led to a landslide in the Yukon River near Whitehorse. This happened very close to the Alaska Highway, clearly visible at the bottom of the photo.

If the destruction of coral reefs has already begun, the rise of temperatures could make this destruction permanent, and thus affect the 500 million humans who depend on it.

In the Labrador Sea, a phenomenon of heat exchange (or convection) that brings warm air to Europe could be disrupted, resulting in colder winters, as the continent experienced them during the Little Ice Age.

Accelerated permafrost thaw would release huge amounts of greenhouse gases and profoundly alter landscapes in Russia , Canada and Scandinavia.

With a warming of 1.5°C, a major ocean current in the Atlantic (the AMOC) would be disrupted and at 2°C the monsoons in West Africa and in the Sahel and the Amazon forest which could then turn into savannah.

The permafrost in regions like the Yukon is ideal for soil samples since ancient DNA is better preserved in the cold.

These devastating effects depend on the duration of warming, explains the #x27;Study lead author David Armstrong McKay: If 1.5°C stays for 50 or 60 years, the planet will face the worst consequences.

But these tipping points will do very little to worsen the warming itself, he adds, believing that humanity can still limit the damage going forward. It is always worth reducing our emissions as quickly as possible, argues the scientist.

Tim Lenton, one of the world's experts on the subject, wants to believe that this concept of rupture can be translate more positively into the fight against the climate crisis, as a sociological tipping point that encourages action.

That's how I manage to get up in the morning, he explains. Can we change, transform our lifestyles? Thinking systemically, with this idea of ​​the breaking point, gives us a glimmer of hope.

The published study in the journal Science (in English)

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