Cloud seeding is an unfamiliar topic to many U.S. citizens, especially those outside of drought-stricken regions of America.
Beyond the image of a factory producing puffs of cloud, cloud seeding is a mystery to most. When I asked my colleagues about what they knew about cloud seeding, they either had no idea what I was talking about or compared it to the practice of “crystal seeding,” where chemists seeking to make a solid crystal of product out of a liquid product will place a grain of ideal crystal (called the seed) into the solution, inducing the formation of a larger crystal of that same structure.
This crystal seeding explanation is closer to reality than puffs of clouds from a factory, but there is more to know about the process of cloud seeding than simply throwing a molecule into the sky.
What is Cloud Seeding? 
Cloud seeding is quite similar to the concept of chemical crystal seeding — DRI, the Desert Research Institute based in Nevada, defines it as “a weather modification technique that improves a cloud’s ability to produce rain or snow by introducing tiny ice nuclei into certain types of subfreezing clouds.”
A typical cloud will start precipitating rain or snow when, as the U.S. Geological Survey informs, “tiny water droplets condense on even tinier dust, salt, or smoke particles, which act as a nucleus, binding them together…If enough collisions occur to produce a droplet with a fall velocity which exceeds the cloud updraft speed, then it will fall out of the cloud as precipitation.”
There are millions and millions of droplets of water molecules in a cloud, and when they interact with an outside particle, they are able to condense and attract other droplets to themself, forming bigger and bigger water drops until they can leave the cloud and fall to the Earth’s surface.
For clouds to actually start precipitating, they need certain ingredients. They need enough moisture in the cloud to facilitate precipitation in the first place, and warm clouds typically require a nucleus particle (smoke, dust, or salt naturally) while cold clouds typically require an ice crystal to start the precipitation.
The great promise of cloud seeding is to improve snowpack on mountains, assuage drought in desert states of the U.S., and lessen hail size and impact. While this solution sounds idyllic, and potentially necessary as shifting precipitation trends leave some areas particularly affected by drought, scientists still don’t have a clear theory about why clouds can precipitate in the first place.
With that lack of base knowledge about the ins-and-outs of clouds, it seems prudent to explore the “paradigmatic” solution proposed by cloud seeders.
Cloud seeding typically involves either flying a plane, launching a rocket, or powering ground-based generators to drop silver iodide as nuclei for precipitation into eligible clouds. The most eligible clouds are the ones with the most moisture content available that simply lacks the “on-switch” of a nucleus to gather raindrops.
Cloud seeding is done by many governments around the world, including big global powers like the U.S., China, the United Arab Emirates, and Russia (formerly the Soviet Union). The practice is largely managed by governmental systems through funding provided to research laboratories at universities, but some in the U.S. is done by nonprofits that partner with universities and depend on donations and grants for their work.
For example, the DRI operates as a sister research facility to the University of Nevada, but has received funding for cloud seeding programs both through private donations made to the DRI itself and through funding from the U.S. Bureau of Reclamation and the National Oceanic and Atmospheric Administration.
How Does Cloud Seeding Work?
Cloud seeding, as discussed before, is a theoretical measure to boost rainfall and precipitation while preventing destructive hail from forming.
It starts on the ground, where scientists and operators will either prepare ground-based generators, rockets, or planes for the mission — to launch silver iodide into potential target clouds and hopefully induce that cloud to rain or snow all the precipitation it possibly can.
The Wyoming Weather Development Office speaks to the ground-based generators, which they use to target clouds passing over the mountains. “The ground-based generators kind of look like small weather stations, are like 20 feet tall, and they aerosolize into the atmosphere. But you have to wait for the right atmospheric conditions so that the plume goes over the mountain range.” The method of ground-based generators is that a desired reagent (like silver iodide) is burnt in combustible mixtures and is taken into clouds by updrafts. This method is purportedly useful because an organization doesn’t have to launch a rocket or fuel a plane to fly through the clouds, but the efficacy of this distribution is questionable.
A 2021 study conducted in east Cuba showed that at two different emission rates, silver iodide from ground-based generators launched either too far under eligible clouds or didn’t actually cause any effective increase in rainfall. Many published papers (like this 2019 paper from Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia) suggest potential efficacy of ground-based generators in terms of comparative cost to other weather management systems, but don’t implement and test their ground-based theories.
The DRI in Nevada claims to use ground-based generators for the majority of their operations, which would certainly save money as opposed to flying over every cloud that they decide to inject with silver iodide or salt, but they also do not go into the details of ground-based generator efficacy.
In terms of rockets launched to seed clouds, the main players are former USSR nations like Georgia, Uzbekistan, and Moldova, with additional evidence of Chinese missile weather control operations (as of 2017). Rockets follow a similar principle, allowing flares or combustible mixtures of cloud seeding particles to be launched directly into clouds. China was reported to use rockets before the 2008 Beijing Olympics to ensure there was a clear sky before the event, and the People’s Daily (a news site from the People’s Republic of China) reported the China Meteorological Administration using “116,000 rain bombs and 25,000 rain enhancement rockets” within a span of less than a month in 2022.
The U.S. doesn’t seem too keen on using rockets, but that makes sense considering the only vague data about their efficacy is coming from the former USSR and the tightly-controlled news system in China, both likely to claim no environmental harm or negative results from cloud seeding practices.
And lastly, there is also plane-mediated distribution of silver iodide into clouds, which tends to be the more frequently used method of cloud seeding in the U.S.. In this method, planes will fly to assigned altitudes and either light flares of silver iodide above susceptible clouds or light flares as they “punch through” clouds.
While this method is theoretically the most effective way to seed clouds because it enables targeted distribution of ice or rain drop forming nuclei, the long-term efficacy of this method (not even considering the price, fossil fuel usage per cloud seeded, and potential intensification of extreme weather events due to global warming patterns) remains difficult to prove worthy.
How can you determine accurately what the projected rainfall from a cloud formation would be if you have no indication if a cloud formation will produce precipitation at all?
And then, how could you predict the projected rainfall versus the actual rainfall with cloud seeding techniques implemented?
Questions about the technicalities of cloud seeding are often left unanswered.
Who Initiates Cloud Seeding?
In the U.S., cloud seeding operations are unregulated by the federal government.
While this may suggest a general disinterest or lack of belief in cloud seeding’s efficacy from the U.S. government, I would posit that U.S. officials still facilitate funding towards this end.
The U.S. Bureau of Reclamation spent $2.4 million on cloud seeding along the Colorado River in 2023. In the West region of America, states like California, Colorado, Idaho, Nevada, New Mexico, Oklahoma, Texas, Utah, and Wyoming use cloud seeding to theoretically assist in filling up reservoirs and rivers.
The DRI, one main source of U.S. experimentation, is funded in part by the U.S. Bureau of Reclamation and the National Oceanic and Atmospheric Administration. The rest are donations from private entities, which could be any company that either maintains purely altruistic motivations to further research, or could be from Big Tech companies that seek the development of such technology to further business interests.
According to Fortune Business Insights, these are a sample of companies (as of 2023) outside of governmental organizations that expressed interest or owned shares in the cloud seeding industry: Weather Modification Inc. (U.S.), RHS Consulting Inc. (U.S.), North America Weather Consultants Inc. (U.S.), Snowy Hydro Limited (Australia), Mettech S.P.A (Chile), 3D S.A. (India), Cloud Technologies GmbH (Germany), Seeding Operations and Atmospheric Research (SOAR) (U.S.), Ice Crystal Engineering (ICS), LLC (U.S.), Charter Flights Aviation (India).
In terms of the countries that are actively using cloud seeding techniques, according to the World Meteorological Organization, 52 or more countries have cloud seeding programs, performed by 34 private weather modification companies. These include the U.S., Canada, some South-American countries, the Middle-east, China, Indonesia, Russia and some EU countries.
Does Cloud Seeding Actually Work?
In summary, we have no idea. It’s likely we will have no idea of the efficacy of cloud seeding until we can monitor drops and cloud patterns with much more sophisticated technology.
Since the start of U.S. cloud seeding in the 1940’s by General Electric, several questions have been raised about the basis and efficacy of cloud seeding in general. In the midst of a push for awareness of climate change, it is important to consider the materials, effects, and consequences of cloud seeding.
- First things first, silver iodide may not be the best choice for cloud seeding.
While silver iodide, a salt compound, was the first choice of scientists Irving Langmuir, Vincent Schaefer, and Bernard Vonnegut (brother of famed science fiction author Kurt Vonnegut), silver iodide may not be the best choice for future weather modification endeavors.
Silver iodide was originally used because of its natural mimicry of the surface of an ice crystal and the ability to nucleate water droplets at -10 to -5 degrees C. Water droplets will typically form pure ice crystals with no nucleus around -40 degrees C, so providing a nucleating molecule can help facilitate a “push” for water to form droplets and ice crystals.
Yet, Dr. Angelos Michaelides, a theoretical chemist at University College London, suggests silver iodide might not even be necessary. After all, if natural clouds nucleate around dust particles and pollen, maybe we don’t need something with a purportedly “identical” structure to crystal ice. He discovered that “there was no simple correlation between the similarity of a surface to ice and its ability to nucleate ice.”
Additionally, in a paper he published in 2009, Dr. Michaelides proved that the formerly elusive crystalline structure of ice was not the hexagonal crystal Schaefer and Vonnegut once imagined — instead, one dimensional ice crystals were strongest in pentagons.
Some scientists have proposed using cells of certain harmless bacteria, whose surface proteins can also freeze water into ice crystals, which may propose less cost than using silver iodide salts or dry ice compounds.
- There are potential long-term environmental risks of large scale cloud seeding.
We cannot promise our kids and grandkids that the use of silver iodide would not cause long-term environmental risks. I’m sure that the folks who first put lead in paint didn’t anticipate it to be the cause of neurotoxicity for their children and grandchildren, and there is a fear that this may be the unanticipated consequence of large-scale use of silver-containing compounds.
Although a compelling argument may be made at this point to suggest that silver iodide present in the soil and water formations under which clouds have been seeded is not at a harmful level, there are also significant risks of silver present as the levels build up over time.
Bioaccumulation is the buildup of material in the environment, especially one in which the material is not easily removed from such an ecosystem. At some point, the material builds up to toxic levels and can seriously harm the environment.
One of the risks of large-scale cloud seeding is the bioaccumulation of silver and silver iodide in the environment. Although silver iodide can be broken down into silver and iodide through the action of ammonia present in the soil, silver iodide is regulated as a “hazardous substance, a priority pollutant, and a toxic pollutant” under the Clean Water Act by the U.S. Environmental Protection Agency.
Bioaccumulation would particularly affect the microbiome of the environment upon which repeated cloud seeding treatment would occur. In a study from 2016, researchers discovered that the effect of repeated treatment with silver iodide could be very harmful to both terrestrial and aquatic bacteria, which could throw the entire microbiome of fragile environments out of normal ranges.
Additionally, there is limited research on the effect of long-term silver iodide exposure to the human body, whether in free silver ions or in the salt form.
- Cloud seeding requires ideal cloud conditions, which are not often present in areas that need it most and may take water from former predicted precipitation regions.
Cloud seeding has been touted as a fix for drought-stricken areas, the savior of deserts that desperately need water for continued survival.
Dr. Heather Holmes, an Assistant Professor in the Department of Physics and Atmospheric Sciences Program at the University of Nevada, notes that “meteorological drought is defined as a shortfall in precipitation over a certain time period, typically over a long period of time like months…because moisture is the first ingredient for cloud seeding to produce rain, cloud seeing cannot be used as a solution to create rain during drought conditions.”
Without moisture and clouds to seed, cloud seeding obviously will struggle to solve major drought in an area. Drought means no moisture. No moisture means no clouds.
Additionally, the phenomena of “robbing Peter to pay Paul” is widely debated. This phenomena argues that the redistribution and modification of weather systems may benefit some individuals in need, but takes precious and expected resources away from another population.
Some experts suggest that cloud seeding doesn’t actually move the distribution of water deposition, but simply optimizes the deposition of water from clouds that may not have been able to naturally produce droplets anyhow. Other experts suggest that there is no way to prove that the water is not “stolen” from target precipitation areas and that water-dependent regions may be disproportionately affected by the effects of cloud seeding.
Water distribution may be affected, and although this may help regions in need of more water supplies, cloud seeding may throw off expected precipitation in regions infrastructurally prepared for smaller or larger amounts of rainfall than they receive.
For example, the U.A.E.’s pattern of cloud seeding to beat their regional desert and drought conditions may have contributed to their recent flood patterns and their inability to rectify large amounts of rainfall. A study published in 2021 notes the U.A.E.’s “cloud-seeding provides water security benefits, [but] its impact on urban flooding should also be carefully considered in the context of urban development plans.”
Additionally, considering the recent extreme flooding in Dubai in April 2024, there are speculations that a changing precipitation climate and cloud seeding efforts alike made the flooding much more dramatic than predicted. Although the U.A.E. released a statement saying they cloud seeded on the preceding Sunday and Monday (not on the Tuesday of the quasi-monsoons), there is speculation if the changing of the precipitation weather patterns could have amplified the effects.
- There is no consensus that cloud seeding is effective…at all.
In all the rigamarole and debacle about cloud seeding, from its genesis to present day, there is no solid scientific evidence that cloud seeding works. It largely operates as a method to allow Big Technology, corporations, and governments to “play God” with unmeasurable efficacy.
From the start, cloud seeding mainly worked in the General Electric laboratory, where Shaefer and Vonnegut played with plane wings. Notably, inside a laboratory context.
In a paper published in 1967, scientists from UC Berkeley noted, “in most American experiments it was hoped to demonstrate that the seeding will increase precipitation. Contrary to this, there is evidence that, if anything, the precipitation was decreased. The purpose of the Swiss experiment Grossversuch III was to demonstrate that hail may be suppressed by seeding. Contrary to this, Paul Schmid produces evidence that the frequency of days with hail was increased by seeding.”
In a publication by the Proceedings in the National Academy of Sciences in 1972, scientists reviewing Arizona cloud seeding experiments determined questionable efficacy. They noted that “the population of experimental days includes two categories with opposite responses to seeding: augmentations of rain in one case and losses in the other.”
With a determined government and a vested corporate interest in changing weather patterns, techno-optimism (the thought that technology can resolve natural problems) reigns supreme.
In 2016, the American Chemical Society published a piece in the Chemical and Engineering News section about cloud seeding, and argued that “it seems odd then that cloud seeding, so heavily touted, hasn’t actually been statistically proven to work..the studies lacked statistical rigor. And running control experiments in cloud-seeding studies is a challenge: Once a cloud is treated, you can’t measure how much it would have rained or snowed if left unseeded. Even the basic mechanics underlying the crystallization of water molecules on seeding agents remains mysterious.”
The American Meteorological Society published a bulletin on the advances of precipitation enhancement research in 2019, saying that “the uncertainties that limit the scientific foundation for cloud seeding, especially for mixed-phase convective clouds, will be reduced through international analysis and model intercomparison workshops, promotion of best practices, and the publication of the data and results of relevant research in the international scientific literature.”
In 2022, the Bulletin of the Atomic Scientists (the researchers that calculate the “doomsday clock” and how close the human race is to global calamity) wrote a report on how cloud seeding could go wrong, including unknown human health and safety concerns, following a system based on the empty promises of lacking research, and redistributing drought and flood risks.
There are many more statements from American scientists that include a lack of confidence in cloud seeding and the efficacy held therein.
If someone is looking for a bandage solution to climate change, this is certainly not the solution to choose. Millions of U.S. dollars have already been carefully poured into the clouds above us, which may have rained without our intervention anyhow.
In no uncertain terms, that means that we are still acting upon a guess, a guess that cannot be founded in its basest assumptions even after almost 80 years of research.
References
Almheiri, K. B., Rustum, R., Wright, G., & Adeloye, A. J. (2021). Study of Impact of Cloud-Seeding on Intensity-Duration-Frequency (IDF) curves of Sharjah City, the United Arab Emirates. Water, 13(23), 3363. https://doi.org/10.3390/w13233363
Benisek, A. (2024, April 11). What to know about Cloud Seeding. WebMD. https://www.webmd.com/a-to-z-guides/cloud-seeding
C&Amp;EN, J. P. S. T. (2022, October 18). Firm footing for cloud seeding. Chemical & Engineering News. https://cen.acs.org/articles/94/i22/Does-cloud-seeding-really-work.html
Carrasco, J., Michaelides, A., Forster, M., Haq, S., Raval, R., & Hodgson, A. (2009). A one-dimensional ice structure built from pentagons. Nature Materials, 8(5), 427–431. https://doi.org/10.1038/nmat2403
Climate change mitigation through weather modification: cloud seeding as a global case study. (2023, December 1). World Meteorological Organization. https://wmo.int/events/cop-event-science-climate-action-pavilion/climate-change-mitigation-through-weather-modification-cloud-seeding-global-case-study
Communication Navigation & Surveillance: Cloud Seeding Market. (2024, August 12). Fortune Business Insights. https://www.fortunebusinessinsights.com/cloud-seeding-market-104073
DeFelice, T., Golden, J., Griffith, D., Woodley, W., Rosenfeld, D., Breed, D., Solak, M., & Boe, B. (2014). Extra area effects of cloud seeding — An updated assessment. Atmospheric Research, 135–136, 193–203. https://doi.org/10.1016/j.atmosres.2013.08.014
Desert Research Institute. (2022, September 19). What is Cloud Seeding? – DRI. DRI. https://www.dri.edu/cloud-seeding-program/what-is-cloud-seeding/
Everts, S. (2016, April 21). Making ice microbe-style. Chemical & Engineering News. https://cen.acs.org/articles/94/i17/Making-ice-microbe-style.html
F. (n.d.). At least 10 Chinese provinces use cloud-seeding to combat heat wave; ‘no effect’ on climate change, ecosystem – People’s Daily Online. http://en.people.cn/n3/2022/0827/c90000-10140421.html
Fajardo, C., Costa, G., Ortiz, L., Nande, M., Rodríguez-Membibre, M., Martín, M., & Sánchez-Fortún, S. (2016). Potential risk of acute toxicity induced by AgI cloud seeding on soil and freshwater biota. Ecotoxicology and Environmental Safety, 133, 433–441. https://doi.org/10.1016/j.ecoenv.2016.06.028
Flossman, A., Manton, M., Abshaev, A., Bruintjes, R., Murakami, M., Prabhakaran, T., & Yao, Z. (2019). Review of Advances in Precipitation Enhancement Research. American Meteorolgical Society, 100(8), 1465–1480. https://doi.org/10.1175/BAMS-D-18-0160.1
Gray, J., & Ramirez, R. (2022, March 4). Scientists in the US are flying planes into clouds to make it snow more. CNN. https://www.cnn.com/2022/03/14/weather/cloud-seeding-weather-modification-wxn/
Ice-Nine’s Concept. (2023, March 27). Chemical & Engineering News. https://cen.acs.org/articles/85/i25/Ice-Nines-Concept.html
King, M. W. (2024, March 21). What if every dark cloud had a silver iodide lining? Clark University. https://clarknow.clarku.edu/2024/03/21/what-if-every-dark-cloud-had-a-silver-iodide-lining/
Korneev, V. P., Potapov, E. I., & Shchukin, G. G. (2017). Environmental aspects of cloud seeding. Russian Meteorology and Hydrology, 42(7), 477–483. https://doi.org/10.3103/s106837391707007x
Kuhl, L. (2022, August 11). Dodging Silver Bullets: How cloud seeding could go wrong. Bulletin of the Atomic Scientists. https://thebulletin.org/2022/08/dodging-silver-bullets-how-cloud-seeding-could-go-wrong/
León, A., Borrajero, I., & Martínez, D. (2020). Study of the dispersion of AGI emitted from ground-based generators using the WRF-Chem model. Atmósfera. https://doi.org/10.20937/atm.52624
Mettler-Toledo International Inc. all rights reserved. (2023, September 20). Seeding studies for crystallization. Mettler-Toledo International Inc. All Rights Reserved. https://www.mt.com/us/en/home/applications/L1_AutoChem_Applications/L2_Crystallization/seeding-cryz.html
Neyman, J., Osborn, H. B., Scott, E. L., & Wells, M. A. (1972). Re-Evaluation of the Arizona Cloud-Seeding Experiment. Proceedings of the National Academy of Sciences, 69(6), 1348–1352. https://doi.org/10.1073/pnas.69.6.1348
Neyman, J., & Scott, E. L. (1967, January 1). Appendix. Planning an experiment with cloud seeding. Project Euclid. https://projecteuclid.org/proceedings/berkeley-symposium-on-mathematical-statistics-and-probability/Proceedings-of-the-Fifth-Berkeley-Symposium-on-Mathematical-Statistics-and/Chapter/Appendix-Planning-an-experiment-with-cloud-seeding/bsmsp/1200514002
Prasetio, A., Widjiantoro, B. L., Nasution, A. M., & Department of Physics Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia. (2019). Overview of ground-based generator towers as cloud seeding facilities to optimize water resources in the Larona Basin. In MATEC Web of Conferences (Vol. 276, pp. 60–25). https://www.matec-conferences.org/articles/matecconf/pdf/2019/25/matecconf_icancee2019_06025.pdf
Precipitation and the water cycle | U.S. Geological Survey. (n.d.). https://www.usgs.gov/special-topics/water-science-school/science/precipitation-and-water-cycle
Silva, B. M. P. &. M. (2024, April 17). What is cloud seeding and did it cause Dubai flooding? https://www.bbc.com/news/science-environment-68839043
University of Nevada, Reno. (2017, March 24). Why isn’t cloud seeding a viable answer to drought? University of Nevada, Reno. https://www.unr.edu/nevada-today/news/2017/atp-cloud-seeding
Wei, L. (2023, August 14). Make it rain: Cloud seeding, the controversial weather modification technique. Le Monde.fr. https://www.lemonde.fr/en/environment/article/2023/08/14/make-it-rain-cloud-seeding-the-controversial-weather-modification-technique_6093144_114.html#
Wyoming Water Development Commission. (n.d.). https://wwdc.state.wy.us/weathermod/