What if we told you that humans have been controlling the weather — or at least trying to — for decades? This isn’t sci-fi, and it’s not just some conspiracy theory, either. Cloud seeding is a real technology with a long and colorful history, and it’s making headlines again as people speculate on its role in today’s increasingly bizarre weather patterns.

First, what is cloud seeding? Cloud seeding is used to augment or suppress weather events, most notably precipitation. It is important to understand that this process is, for better or worse, human intervention in the weather. Moreover, this intervention can be accomplished with planes or drones, but this is only one method of cloud seeding developed in the history of this process.

Several questions and uncertainties surround the long-term effects and unpredictability of weather manipulation, not to mention the historical abuses for which this technology has already been used.

Scientifically speaking, cloud seeding introduces compounds or particles to a storm system to induce precipitation. Per Earth.org, the compound that is most commonly used is silver iodide (AgI), but others include sodium chloride (NaCl), calcium chloride (CaCl2), potassium iodide (KI), dry ice (solid CO2), sulfur dioxide (SO2), bismuth tri-iodide (BiI3), and propane (C3H8). Regardless of the compound, the released particles imitate the formation of ice crystals in the clouds, allowing for moisture to "latch onto" these artificial compounds. The weight of these “nuclei” then induces rain to fall from the clouds.

Silver iodide is the preferred chemical because its structure is quite similar to that of natural ice crystals. Furthermore, a single gram of silver iodide can induce trillions of artificial ice crystals. This is naturally a favorite compound because not only is it structurally very similar to the ice crystals, but it is also very cost-effective.

Cloudy origins

The official discovery of cloud seeding methods is credited to Vincent Schaefer and Bernard Vonnegut (yes, the older brother of Kurt Vonnegut). They separately discovered two different methods around the same time: one using dry ice to alter the heat of the cloud system and the other involving the chemical manipulation of the clouds to simulate the formation of ice crystals. In the end, however, cloud seeding is accomplished in both ways, seeking to manipulate the ice crystals in the clouds. General Electric discovered and developed these methods in 1946. Both methods are still used to this day, usually using dry ice and silver iodide, respectively.

Many of the purported mainstream uses for cloud seeding are banal, although the fact that this technology exists and has been utilized for decades is not. According to Earth.org, cloud seeding is used by governments to supplement the water supply in drought-stricken areas, suppress extreme heat, control wildfires, and improve agricultural productivity. On the other hand, ski resorts, insurance companies, and airports sometimes employ this technology to increase snowfall, mitigate hailstorms, or disperse fog, respectively.

Interestingly, not all applications of cloud seeding technology have been so benign. For example, the United States military used cloud seeding technology in the Vietnam War from 1967 to 1972 in a project known as Operation Popeye. According to a New York Times article published in 1972, this project sought to extend the monsoon season in North Vietnam to affect military operations during the war, especially along the Ho Chi Minh Trail. It was hoped that the increased rainfall during monsoon season would cause landslides and destroy roads, disrupting North Vietnam’s military supply chains and troop/arms movements.

What’s more, the report indicated that “many usually well‐informed members of the Nixon Administration had been kept in the dark.” According to a “well-placed government official,” this operation was kept under wraps even within the government itself: “This kind of thing was a bomb, and Henry [Kissinger] restricted information about it to those who had to know.” The article suggests that Henry Kissinger played a direct role in this project and its concealment within the government.

According to Earth.org, cloud seeding for military use was suspended in a 1977 international treaty, yet this historical example demonstrates this technology's wide range of applications.

Making it rain

New innovations have seemingly streamlined the cloud seeding process in some experiments. For example, it was reported that the “United Arab Emirates began to experiment with the use of aerial drones for cloud seeding.” As the article explains, “The new twist on the old concept uses drones to cast an electric charge. This ‘zaps’ clouds with a laser beam, which causes water droplets to combine and leads to rainfall.” While the science behind this particular experiment is not as clear, this does show that the technology is improving and that many countries are attempting to refine this process. More broadly, we can conclude that this technology has existed for a long time, is explainable, and is certainly not "magic." In true "Jurassic Park" fashion, however, there is, of course, an ethical debate that should supersede the scientific inquiry.

Cloud seeding can produce many positive effects. It can bring more water to arid lands, like the Western United States or some parts of China. It can also shape weather events for less utilitarian purposes. For example, China used this technology during the 2016 Beijing Olympics and claims that it “cleared the skies for the Beijing Olympics by forcing the rain to come early.” It can ostensibly stop or shrink the size of hail. It can also potentially mitigate harmful weather events such as hurricanes or monsoons.

However, cloud seeding could have some negative consequences. First, weather is evidently unpredictable, so even if we can influence the weather, we cannot fully control it. According to a government official familiar with Operation Popeye at the time, there was a large margin of error in the experimental phase of the project: “We used to go out flying around and looking for a certain cloud formation,” the official said. “And we made a lot of mistakes. Once we dumped seven inches of rain in two hours on one of our Special Forces camps.”

Second, silver iodide, the popular compound used in the cloud seeding process, is mildly toxic to humans over long periods of time: “Ingestion of silver iodide can lead to nausea, vomiting, and diarrhea. Prolonged exposure to silver iodide can cause argyria, a condition where silver deposits in the tissues, causing them to turn blue or gray.” Most sources claim that the concentration of silver iodide in water produced through this process is negligible. Taking these sources in good faith, it should nonetheless be noted that our evidence is likely to reflect small areas of land over a shorter period than would be preferable. That is to say, we do not know the long-term effects of silver iodide in the water for a larger population, like the United States.

It is astounding that this technology exists and seems to be somewhat effective. It is a true feat of human ingenuity. This technology has many potential benefits, and it is hoped that entities equipped with these capabilities will use them well. We should also be more informed about developments of this technology in the future. Several questions and uncertainties surround the long-term effects and unpredictability of weather manipulation, not to mention the historical abuses for which this technology has already been used. These questions should be answered before this tech is expedited or expanded to a larger scale of operation. Let’s hope that, as more people learn about this reality, there is a stronger push for an ethical debate to develop alongside this incredible feat of science. If scientists must “play God,” as some critics say, we should at least proceed very cautiously.