“Bell” for climate: Consequences “of no return” if the earth’s temperature rises above 1.5° C

If the temperature on the planet rise beyond 1.5° Celsiusin other words if not observed the most ambitious goal of the Paris Agreement to the climate, there may be changes that will be “irreversible” and trigger catastrophic chain reactions, warns a study published yesterday Thursday in the scientific journal Science.

Current temperatures, already on the risethreaten to trigger five such changes, especially in the Antarctic and Greenland glaciers, warn the authors of the study, who judge, however, that it is not too late to take action.

“To me, that would change the face of the world — literally, if you look at it from space,” with rising ocean levels and deforestation, Tim Lendon, one of the study’s lead authors, told AFP.

He had signed the first major publication on the issue in 2008.

A “climate tipping point” is “the critical threshold beyond which a (climate) system is reorganized, often violently and irreversibly,” as defined by the UN Intergovernmental Panel on Climate Change. These are phenomena that trigger, in an independent and inescapable way, chain reactions.

Although initial analyzes estimated that the threshold for these effects ranged between 3 and 5°C, advances in observations, climate models, and the reconstruction of paleoclimate conditions have drastically reduced the estimate.

The study published in Science is a synthesis of more than 200 scientific publications. It was conducted to more accurately predict the boundaries of these ‘tipping points’.

The authors refer to nine major “turning points” at the planetary level and seven at the regional level, a total of 16.

Among them, five may be triggered even with today’s temperatures, which have increased by 1.2°C compared to pre-industrial times: the melting of the Antarctic and Greenland ice sheets, the rapid melting of permafrost, the disruption of effect of heat transfer in the Labrador Sea and the elimination of coral reefs.

If the temperature rise reaches 1.5°C, another four points will move from “possible” to “probable” and another five will also become “probable”, according to the study.

“Sociological turning point”

For the ice sheets in West Antarctica and Greenland, exceeding the tipping point, scientists estimate, will cause the sea level to rise by 10 metersalthough it could take hundreds of years for that to happen, according to Tim Lendon of the UK’s University of Exeter.

Although the destruction of coral reefs has already begun, rising temperatures may make it final, hitting 500 million people that depend on them.

In the Labrador Sea, the heat transfer effect, which drives warm air to Europe, can be reversed, which will mean much harsher winters on the Old Continent, as during the so-called Little Ice Age (early 14th-mid 19th century) .

If the melting of permafrost accelerates, huge amounts of greenhouse gases will be released and will dramatically change the landscapes in Russia, Canada, Scandinavia.

With a global temperature rise of 1.5°C, one of the most important ocean currents in the Atlantic (the Atlantic Meridional Overturning Circulation, or AMOC) will be disrupted, and if the temperature rises by 2°C, so will the monsoons in western Africa, the Sahel and the Amazonian forest, which can consequently transform into a savannah.

These devastating consequences depend on how long the rise in temperature will last, according to another of the study’s authors, David Armstrong Mackay: if its increase of 1.5°C lasts 50 or 60 years, the planet will live the worst.

But these “tipping points” do not in themselves affect the increase in temperature, he added, estimating that humanity can still limit the damage. However, it remains necessary to “reduce emissions” of greenhouse gases “as soon as possible”, the scientist insisted.

Mr. Lenton, one of the best-known experts on climate change internationally, wants to believe that the idea of ​​a “tipping point” can also be translated, positively in this case, into the fight against the climate crisis: he speaks of a “sociological tipping point turning point’, which will encourage the transition to action.

“This allows me to get out of bed in the morning (…). Can we change, can we transform our way of life? Looking at it systemically, this idea, of the tipping point, offers us a glimmer of hope.”

RES-EMP

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