Juline Garnier 11:44 am, June 17, 2023

Faced with droughts that threaten agricultural production and ecosystems on a global scale, scientists and tech entrepreneurs are thinking about creating new technologies to mitigate the effects of global warming. And in the first place is geoengineering. Miracle solution or chimera of the "techno optimists"? Elements of response.


Once feared and uncontrollable, will the weather finally be controlled by humans? If the question seems like science fiction, it is very real in the minds of scientists, worried about the speed at which the effects of global warming are being felt and the very weak action of governments. For the past ten years, the idea of geoengineering has been charting its course and is one of the solutions evoked by "optimistic technos", or in other words those who think they can solve the climate crisis through new technologies.

As early as 2014, this term appeared in the IPCC synthesis report on climate change. Geoengineering is defined as a "broad set of techniques that operate on a large scale and aim to deliberately alter the climate system" to combat warming. These methods include carbon dioxide storage, solar radiation management or cloud seeding or "artificial rain".

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The IPCC remains cautious

And since then, entrepreneurs have been scrambling to develop these technologies, especially for carbon capture. Elon Musk's XPrize Foundation, for example, allocates $100 million each year to the development of these processes. If the IPCC recalls however that there is little evidence to assess "their feasibility, cost, side effects and impact on the environment", artificial rain has a head start.

Because scientists know how to create it. Tested previously - and unofficially - in a military setting in 1962 as part of "Operation Popeye", artificial rain is achieved by injecting silver iodide into a cloud, if it has a temperature below 0 ° C. Otherwise, hygroscopic salts can be used. These effective methods have been tested several times in the Middle East and China to combat soil drought. And even in France via the National Association for the Study and Fight against Atmospheric Scourges (Anelfa), but this time to prevent heavy hail.

A miracle solution?

So, miracle solution? Not quite, because as Jean-François Berthoumieu, director of the South-West Climate Association, reminds us, "We do not make rain when the sky is blue". Interviewed by Socialter in an issue dedicated to geoengineering, he remains skeptical. Because each cloud - when there is one - is unique and the precipitation capacities are multiple. "It's impossible to say that we already know what will happen when we seed a cloud," he told Socialter.

In addition, the question of the risks of toxicity of the use of silver iodide arises. While Anelfa claims that its use for cloud seeding is not dangerous, scientists remain cautious. An English study conducted by the Centre for Ecology and Hydrology in the early 2000s reveals that silver iodide, below a certain concentration, is not toxic to the environment. But this substance is described as "extremely insoluble": the risk is therefore that it accumulates and that it can, in the end, be harmful.

With global warming and the increase in drought periods, the issue of access to water and its quality will take a central place in the coming years in government strategies. In March, the UN organized a major conference to "avert a global crisis" of water, recalling that today, two billion people do not have access to safe drinking water, and 3.6 billion lack safely managed sanitation systems.