The tipping point of climate change that worries scientists

One of the main challenges of the climate COP26 in Glasgow is to keep alive the goal of limiting the average increase in the planet’s temperature to + 1.5 ° Celsius, but scientists fear other threats: the so-called tipping points, or no return. .

There are several places on the planet that are exposed to such decisive moments, in which their ecological destiny can tilt one way or the other.

And the entire planetary ecosystem depends on those intricate knots.

In Greenland and Antarctica, the thawing of huge frozen expanses could raise the average level of the oceans by more than a dozen meters.

In the Amazon, the rainforest can undergo a process of “savanization” that would irreparably affect the planet’s ability to recycle CO2.

Siberia represents a huge deposit of CO2 that could end up in the atmosphere if the permafrost dissolution process extends.

“We have already detected several tipping points in coral reefs and polar systems, and with global warming projections in hand, there will likely be others in the short term.”, Warned a draft of the UN Intergovernmental Group of Experts on Climate Change (IPCC) to which the AFP had access.

Irreversible points

Many of those points are already irreversible.

The founder of the Potsdam Institute for Climate Research, Joachim Schellnhuber, recalls how he realized fifteen years ago those defining moments in the history of climate change.

“I realized that the machinery of the planet, be it monsoons, ocean circulation, ocean currents, have many non-linear systems. That means there are many points of no return.”, He explained.

In Antarctica, portions of frozen masses the size of Scotland and England could at some point collapse into the ocean, due to global warming, which cracks that region.

“It is like uncorking a bottle. We are uncorking them one after the other”, Explica Schellnhuber.

Climate change and deforestation have also caused a large part of the Amazon region to stop absorbing CO2 and start emitting it.

That transformation could turn one of the great allies against climate change into an enemy.

Scientists struggle to determine what temperatures cause the point of no return in an ecosystem.

But the challenge is enormously complex because prediction models are based on an ever-changing, unpredictable atmosphere.

To this is added the continuous contribution of CO2 and methane of human origin.

“Tipping points are key, existential risks, and we have to do everything we can to avoid them.”Explained Tim Lenton, director of the Institute for Global Systems at the University of Exeter and an authority on the subject.

Fifteen points

Scientists have discovered 15 significant tipping points, some regional, some global, all interconnected.

Parts of the climate system that are more resistant to rising temperatures include currents that redistribute heat through the oceans, such as the El Niño phenomenon in the Pacific, the Southeast Asian monsoon, or desertification in the African Sahel.

Although the permafrost in Siberia does not have a temperature threshold that is going to cause a dramatic change, its slow thawing would release tens of billions of tons of CO2.

The IPCC has published five major reports over three decades on climate change. And in the next, according to the draft that the AFP had access to, the turning points take an increasing role.

“Abrupt responses and tipping points of the climate system or can be ruled out”, Creates this group of experts.

The threat was always present, but it is difficult to realize it because climate models are built on long series of scientific observations.

“I’ve been saying for a decade that we need to take this risk seriously, and that the IPCC should give the tipping points more importance”Explains Lenton.

Some partial studies already address the direct physical consequences. For example, the acceleration of the thaw in Greenland will affect the circulation of currents in the Atlantic, and will push tropical rains south, weakening the monsoons in Africa and Asia, which are vital for the crops of millions of people.

Those currents could disappear, as has already happened in the past. Which would cause European winters to be much harsher, while the water level would rise substantially in the North Atlantic.

The doubts remain because, at the same time, traces of the past indicate that the Earth could be heading towards excess heat, according to the latest IPCC report.

The last time the atmosphere withstood the current levels of CO2 concentration, three million years ago, temperatures were at least 3ºC higher than they are today, and the oceans, between 5 and 25 meters higher.

That trajectory could lead the planet to a situation of no return in less than a century, explains Jan Zalasiewicz, professor of paleobiology at the University of Leicester.

According to another expert, Johan Rockstrom, “from the moment in which the Earth’s systems go from cooling, as is the case today, to heating, there we will lose control ”.