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Several planes cut through the storm clouds when a downpour hit the United Arab Emirates earlier this summer. They had been sent by the authorities in the drought-stricken desert country and brought with them salt which was supposed to significantly increase the amount of much-needed rain.
The rain in the UAE ended up being unusually heavy, but it is unclear how much of it was related to the salt released from the planes. Nevertheless, several other countries have in recent years started working on experiments with technology that can create artificial rain.
These are primarily other countries on the Arabian Peninsula, but the technology has also attracted interest in several U.S. states. In Idaho, which also suffers from drought, two million U.S. dollars per year have been set aside for a program that will create artificial rain. And in the neighbouring state of Utah, there is hope that the technology can save The Great Salt Lake from shrinking.
The most ambitious plans are probably to be found in China. The Chinese government has started a program that aims to be able to manipulate the weather in an area spanning 5.5 million square kilometres. In doing that, the government hopes to be able to prevent water shortages, forest fires, and droughts. According to CNN, the country has invested over a billion U.S. dollars into the technology.
The technology for creating artificial rain is called cloud seeding and is actually about 75 years old. It was, among other things, used during the 2008 Olympic Games in China, where it caused quite a stir.
Traditionally, cloud seeding consists of spreading chemicals such as silver iodide over rain clouds. This is done using aircraft or rockets. In order for it to rain, the water particles in the cloud need a so-called ice nucleus around which they can gather. The chemicals that are sent up act as an artificial ice nucleus, which should be able to induce rain.
This method is still used today in many places, but there are also newer versions of cloud seeding technology. For example, Dubai uses drones that emit electric shocks to the clouds. This should cause the formation of large raindrops and thus reduce evaporation.
Although scientists and engineers in several countries are putting serious work into the technology for creating artificial rain, weather modification is associated with some fundamental problems.
First of all, the effectiveness of cloud seeding is somewhat questionable, according to Eigil Kaas, professor and scientific leader of the National Centre for Climate Research at DMI. He has not directly worked on cloud seeding—in fact, no one in Denmark has—but he is familiar with the technology through his work as a meteorologist.
“It may work in some cases, but it’s often very difficult to document an effect. The fact is that the weather also changes naturally. Therefore, statistically speaking, it’s difficult to prove that it is the technology that has produced the rain,” he says.
Even if the technology actually has an effect, it depends on the atmospheric conditions. There are several elements that play a decisive role in this. Among other things, the water vapor in the atmosphere must condense and form clouds. In simple terms, we can say that the technology can only induce rain if there is already a potential for it in the atmosphere.
“There may be situations where it’s close to raining, but it doesn’t actually happen. One could perhaps use cloud seeding to induce rain in such situations, at a time when water is really sparse,” Eigil Kaas says.
However, if the technology succeeds in producing rainfall, another problem arises. Cloud seeding does not create water in itself but can at best force rain from the water that has already evaporated into the atmosphere.
“If one steals water in a specific area with this method, there is another area that doesn't get the rain. It could potentially be an area where that rain would have been highly appreciated,” Eigil Kaas says.
The artificial rain can, of course, also fall over an area where water is needed to grow crops or be triggered before a violent cloudburst hits a big city. But if drought problems become more widespread in the future as a result of climate change, it is far from unthinkable that rain theft could pose a problem.
Even so, Eigil Kaas is not surprised that some countries are experimenting with the technology.
“If it works, there’s a lot of money in it. If you can make an area wetter than it would otherwise have been, it can really benefit agriculture a lot. But as I said, I’m quite sceptical of how well it really works,” he says.
