We are in 2100. The planet lives to the rhythm of cyclones, storms and heat waves.

Coastlines have been submerged, forcing entire populations to relocate.

Entire species have been wiped out.

In their latest report, published in mid-August, UN climate experts are unanimous: this disaster scenario is increasingly realistic.

The only way to avoid it?

Managing to keep global warming below the fateful threshold of +1.5 ° C. 

As the states of the world are preparing to meet for COP 26 in Glasgow, from October 31, researchers are considering another solution to "save the planet". Rather than relying on a common effort to reduce CO2 emissions, they want to use geoengineering and fix, using technology, what humans have messed up. 

"Geoengineering brings together the different techniques that aim to correct, on a large scale, the effects of human action on the environment", explains to France 24, Sofia Kabbej, researcher in the Climate, Energy and Security Pole of the Institute of International and Strategic Relations (Iris).

Science fiction or reality?

"We are now between the two", assures France 24 Roland Séférian, climatologist for Météo-France, who closely follows the related work.

Modify solar radiation 

In reality, behind geoengineering lies a myriad of projects.

Some seem totally fanciful, even dangerous.

Others, on the other hand, have already materialized. 

"Geoengineering is divided into two main categories", summarizes Roland Séférian. The first - the most controversial - brings together all the techniques aimed at "modifying solar radiation". One of them consists, for example, in injecting it with aerosols into the stratosphere. "The idea is to reproduce what happens during volcanic eruptions when clouds of dust form and form a screen between the sun and the Earth, thus cooling the atmosphere", explains the climatologist. 

For the moment, the project has not crossed the walls of the laboratories. But for several years, a team of Harvard researchers, led by scientist David Keith, has been aiming to test it in real conditions. In 2021, she hoped to launch two balloons into the stratosphere in Sweden and drop a few kilos of calcium carbonate. But faced with the disapproval of the population and the opposition of many NGOs, the project was aborted. 

Another technique is to "whiten" sea clouds by spraying salt into the atmosphere.

The objective: to slow down the warming of the oceans.

The whiter the clouds, the more they reflect the sun's rays and return heat, thus limiting the warming of the waters below.

Here too, research is still in its infancy, even if a first experiment has already been carried out at the local level, in 2020, in Australia. 

Dozens of other avenues, often presented as eccentric and totally unrealistic, are the subject of fantasies: installing mirrors in space, genetically shrinking humans, even modifying the trajectory of the Earth ... 

Capture CO2 

The second major category of geoengineering brings together "CO2 capture or storage" projects. “Unlike the modification of solar radiation, certain avenues have already been widely explored,” explains Roland Séférian. But there again, there are a multitude of techniques: using natural carbon sinks such as forests or oceans, installing CO2 vacuum cleaners everywhere or even putting filters on factories. "There is one that we already use very frequently, it is to plant trees to capture CO2," notes the climatologist. 

Two technologies are now taking a growing place in the scientific community, to the point of being taken into account in the different scenarios of the IPCC report. The first is direct air capture (CDA). The principle is simple: it is about installing kinds of CO2 vacuum cleaners. The captured carbon is then buried underground. In total, according to the International Energy Agency, around twenty projects are already in place around the world. The Swiss company Climeworks, for example, installed these sensors on the roof of a waste incineration plant in the Zurich region. 

The second is "bioenergy with carbon dioxide capture and storage" (BECSC).

In practice, this involves producing energy by burning biomass (wood, agricultural waste, etc.) while trapping the CO2 emitted and then burying it, again, in the ground. 

Here again, no technique has yet fully proved its worth.

CDA appears to be inefficient and requires a lot of energy to operate.

In addition, planting forests or resorting to BECSC raises the question of available arable land.

The myth of a quick fix 

The vast majority of environmental defense associations are upset against geoengineering but especially against the modification of solar radiation.

According to them, the idea of ​​artificially manipulating the climate is unnatural.

"The use of these techniques does indeed pose a major philosophical question. How far do men have the right to go?" Asks Sofia Kabbej.

"To use the modification of solar radiation would be to raise the human to a quasi-divine status. And that is, of course, problematic." 

Many fear, above all, that this research will fuel the myth of a miracle solution.

Why make efforts in the face of global warming, if it suffices to wait for technology to provide a solution? 

The refractories are all the more wary as these projects are, for some, financed by billionaire entrepreneurs like Bill Gates or Elon Musk, for others, by companies like Total.

“Behind the capture of CO2, there is a huge financial opportunity for oil companies,” recalls Sofia Kabbej.

"For good reason, this can only happen through the transport of carbon. A transport that requires pipelines, storage spaces ... In short, the infrastructure they already have." 

Consequences that are difficult to understand 

Moreover, if these solutions can bring their share of hope in the face of a world where climate forecasts are more and more alarming, they all remain uncertain, imperfect, with consequences that are difficult to apprehend.

"Regarding the modification of solar radiation, the techniques are very intrusive. Even with the best models, it is very difficult to know precisely what can happen," notes Roland Séférian. 

"But CO2 capture and storage projects also raise questions," he continues.

"What happens if the carbon leaks during transport? How long can it stay in the basement?" 

Not to mention that the use of geoengineering would pose another major concern, that of governance.

"All the experiments are now carried out by northern countries", notes Sofia Kabbej.

"Using geoengineering would therefore inevitably reinforce North-South inequalities. The countries of the North will be the only ones able to develop these technologies, while it is the countries of the South which will be the first to be affected by the consequences of global warming." 

"We cannot be 100% sure that we will never need it" 

So in the scientific community the debate rages on: should we or should not continue research in geoengineering?

"For me, we should not deprive ourselves of it", pleads Olivier Boucher, research director at the CNRS and specialist in the question, contacted by France 24. "We cannot be 100% sure that we are not. 'We will never need. Conversely, we will perhaps show that these techniques are not viable. In any case, it would be a shame to deprive future generations of our work. " 

"We are in debates close to those on the atomic bomb. We are faced with technologies which, if they worked, would be of unprecedented power," said Sofia Kabbej. 

For Olivier Boucher, it is in this debate that the division into two categories of geoengineering becomes essential. "Anything to do with altering solar radiation should be seen as a last resort. But CO2 capture and storage techniques could, in my opinion, really become additional tools in the fight against global warming." 

A position shared by Roland Séférian.

"To achieve carbon neutrality, it's a safe bet that you will have to use CO2 capture tools," he explains.

"And the more we fall behind in our current policies to fight against global warming, the more it will become inevitable."

And the scientist insisted: "Ideally, I would like that we never get there and that we are able to act without it." 

The need for a public debate 

Anyway today, the research continues.

“And unfortunately, no international framework governs work on geoengineering,” says Sofia Kabbej.

A convention prohibiting the use of environmental modification techniques for military purposes was adopted in 1976, but it remains very limited.

States - which are more and more numerous to release funds - and private actors can therefore develop their projects freely. 

"Today, we are still at the beginnings of geoengineering. But it is certain that the question will become central in a few years", insists Sofia Kabbej.

"It is necessary that the States get around the table of discussions." 

"It is necessary that the subject arrives in the public debate", abounds Roland Séférian.

"Because geoengineering poses a major societal question, relating to the planet. We must discuss it now to sort out what we accept and what we refuse." 

At COP26, however, the subject will not be the subject of official discussions.

"We will certainly talk about CO2 capture and elimination projects, but the subject should not be widely discussed," concludes the climatologist.

"For now, the priority remains to limit our CO2 emissions. Geoengineering may come later." 

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