To make it rain on command, an unchanging dream that lives on today

Manipulating clouds to induce rain or reduce hail: Against the background of global warming, many countries are increasing their interest in these techniques, with the risk of creating geopolitical tensions.

In Australia, the electric company Snowy Hydro is currently completing its traditional seeding campaign in the Snowy Mountains, the highest mountain range on the island continent.

Objective: increase snowfall using a silver iodide particle generator. Snowy Hydro will thus supply water reserves to produce more hydroelectricity, the company explained in an email to AFP.

Whether for agriculture, human consumption or electricity, the huge demands for water have been further exacerbated by global warming. According to UN data, 2.3 billion people already live in countries where water scarcity is a problem.

In such conditions, many countries are trying to change the time: India, Thailand, the United States, but also China. In 2020, Beijing issued a circular detailing its strategy: according to this document, China will have a developed weather modification system by 2025.

The United Arab Emirates is also working hard. The National Weather Center launched a research program to improve rain several years ago, with $1.5 million in grants for each selected research project.

International law

Since the rain nymph fables of antiquity, hopes of producing rain on demand have never dried up. From the late 1940s, the United States launched attempts, including for military purposes: during the Vietnam War, “Operation Popeye” launched by the US military consisted of seeding clouds in an attempt to slow down Ho Chi Minh’s troops. The effectiveness of the maneuver remains a matter of debate.

Since then, the techniques have fluctuated relatively little, although research is ongoing. They generally consist of the dispersion of particles – silver iodide, hygroscopic salt, etc. – in clouds, either by aircraft, or by ground-based generators or rockets. The mini-particles introduced into the cloud will then modify its structure and potentially cause it to settle.

But sowing has pitfalls. Especially since it is difficult to assess the actual effectiveness of the techniques. In France, the National Association for the Study and Combat of Atmospheric Pests (Anelfa), founded at the turn of the 1950s, practices this technique to try to reduce hail that damages agricultural crops. “Effectiveness is still difficult to assess because there is great variability in this natural phenomenon,” admits Claude Berthet, its director.

“But our readings show a correlation between the areas that received silver iodide and those that received the least amount of hail.” Snowy Hydro, for its part, is talking about 14% more snow in the Snowy Mountains during the seeding campaigns.

This is only part of the problem. “The main idea in the context of climate change is that we are moving towards scarcity of water resources, which will produce more and more conflicts over these resources,” warns Marine de Guglielmo Weber, a researcher at the Institute for International and Strategic Relations, who devoted his thesis to the topic.

In this context, “techniques that are presented as being able to force a cloud to settle when it would otherwise take hours will become increasingly suitable for conflict.” In 2018, a senior Iranian official, for example, accused Israel of stealing Iran’s clouds.

However, laments author and former lawyer Mathieu Simonet, who just published a story on the subject, there is no international cloud law. “Clouds correspond to the commons, so we need common rules to share them,” he argues.

“Above all, these common rules must not be determined by the geographical position in which we are: clouds circulate everywhere. Likewise, they must not be determined by the technical capabilities and wealth of this or that country.”

Meanwhile, the author scours France to campaign for International Cloud Day.

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