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Cloud seeding is a controversial topic. While advocates supporting it cite studies that show a 10-15% increase in rainfall due to it, those who oppose it cite hazards that come along with it, such as damage to our safety and environment. Getting to the bottom of the debate would require studying the phenomenon in detail. Only then would we be able to make an informed judgment.
What is Cloud Seeding?
The Desert Research Institute, a well-known leader in basic and applied environmental research worldwide, defines Cloud Seeding 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.”
Clouds consist of tiny water droplets or ice crystals. These droplets or crystals form when water vapor in the atmosphere cools and condenses. The dust or salt particle, randomly floating in the atmosphere, around which these crystals form, is the ice nuclei.
It is these ice nuclei that are introduced to the sky during cloud seeding. They help snowflakes to form by providing a base. Eventually, these snowflakes fall back from the clouds to the earth's surface.
Cloud Seeding Techniques
Cloud seeding happens through two broad techniques. The first one is hygroscopic for warm clouds, and the second one is glaciogenic for supercooled clouds. Seeding of warm clouds could further have two routes:
(i) Water drop technique
(ii) common salt technique.
The seeding of cold clouds can be achieved by dry ice seeding and silver iodide seeding.
Warm Cloud Seeding: Water Drop technique
This technique operates on the principle of coalescence. It aims to introduce sizable water droplets or hygroscopic particles into warm clouds. Typically, this involves dispersing water droplets, each measuring about 25 mm, from an aircraft. The application rate for this process is approximately 30 gallons per seeding event, targeting warm cloud formations.
Warm Cloud Seeding: Common Salt Technique
Common salt is used as a common seeding material in this process in the form of a 10% solution or solid. For practical applications, the salt is used as part of a salt and soap mixture. To facilitate the dispersion of this mixture, tools such as power sprayers, air compressors, or ground generators are used.
Another technique of carrying out this process involves the balloon burst technique, where gunpowder and sodium chloride are arranged to explode near the cloud base to disperse the salt particles.
Cold Cloud Seeding: Dry Ice Technique
Dry ice is nothing but carbon dioxide in solid form. It maintains a temperature of -80 degrees centigrades and is evaporative at this temperature but does not melt. And since it is heavy, it falls rapidly from the top of the cloud.
This process of cold cloud seeding is carried out through aircraft flying across the top of a cloud to release dry ice pellets of size between 0.5-1.0 cm in a steady stream. When these ice pellets fall through the cloud, they form a sheet of ice crystals. As a result of this formation, raindrops fall from these ice crystals.
Cold Cloud Seeding: Silver Iodide Technique
This technique utilizes minute crystals of silver iodide produced in the form of smoke. These crystals, maintaining a temperature of -5 degrees centigrades, act as ice-forming nuclei.
Ejected from ground generators, these fine particles diffuse with air currents. However, proponents of this technology feel that the appropriate procedure for seeding cold clouds would be to release silver iodide smoke into supercooled clouds from an aircraft. This technique is more efficient than the dry ice technique because the requirement of silver iodide is far less.
These techniques of cloud seeding have emerged over the years. However, the first experiment with cloud seeding dates back to more than 75 years.
A Brief History of Cloud Seeding
American chemist and meteorologist Vincent J. Schaefer conducted the first cloud-seeding experiment in 1946. In this landmark experiment, Schaefer dropped six pounds of crushed dry ice into a cloud in the Adirondack Mountains of New York.
Immediately one year later, in 1947, Project Cirrus came along as a collaboration between GE and the United States military as science's first attempt to modify a hurricane. The project dropped nearly 200 pounds of dry ice into a cyclone that hit and passed through the coast of Florida.
The next one came un the early 1960s, named Project Skywater, a series of cloud-seeding experiments funded by the Bureau of Reclamation. The aim was to boost water resources in the western part of the United States.
In Australia, the Commonwealth Scientific and Industrial Research Organization (CSIRO) conducted major cloud seeding trials between 1947 and the early 1960s. In these experiments, the scientists dropped dry ice into the tops of cumulus clouds, used both ground-based and airborne silver iodide generators, etc.
The United States Military carried out further cloud seeding experiments in the late 1960s and early 1970s. The goal was to use weather modification as a weapon of war. The military reportedly planned Operation Popeye to generate enough rainfall to disrupt enemy supply routes in Vietnam. These sorts of military maneuverings came to a halt in 1977 when an international treaty banned the use of weather modification for military purposes.
However, the research around it did not stop. It has been adopted and tried out in many forms on almost all continents across the world.
As recently as late November 2023, the government of Delhi, India, decided to proceed with cloud seeding-induced artificial rain to combat the air pollution in the capital city. The plan was to spray a mix of potassium iodide, silver iodide, and dry ice on clouds via aircraft.
The Directorate General of Civil Aviation approved the aircraft and flares for this specific purpose. Following this approval, a six-seater Cessna plane was chosen to fly over Delhi's sky, responsible for introducing the mentioned chemicals into the clouds.
However, according to Jai Dhar Gupta, a clean air activist and Wharton School alumnus who also has a degree in Environmental Science from the University of Pennsylvania:
“Cloud seeding is a smoking mirror tactic and makes no sense. Post-rainfall, due to an increase in the humidity in the air, the pollution will increase because everything [fuel, biomass, etc.] will release more pollutants.”
And with this skepticism around cloud seeding comes the need to weigh its benefits and drawbacks.
The Benefits of Cloud Seeding
The primary purpose that cloud seeding serves globally is enhancing winter snowfall and increasing mountain snowpack, thereby supplementing the natural water supply available to communities in the surrounding areas.
To evaluate the effectiveness of this approach, scientists have carried out multiple studies on the effect of cloud seeding. While different projects yield varying results, there are numerous instances of notable success. Illustrating this, long-term cloud seeding projects over the mountains of Nevada and other parts of the world have demonstrated an increase in the overall snowpack in targeted areas by 10% or more per year.
The Desert Research Institute designed a five-year cloud seeding project in the Snowy Mountains of New South Wales, Australia. The result was a 14% increase in snowfall across the project area.
Another cloud-seeding experiment carried out in Wyoming lasted for ten years. It took place in the Snowy Range and Sierra Madre Range.
According to data presented by the Wyoming Water Development Office, the experiment showed results by increasing the snowpack from winter storms by five to 15 percent. Another high altitude controlled generator-induced cloud seeding experiment showed snowfall increases of up to 15 percent in the bridger range of Western Montana.
Despite these successes, cloud seeding has gone and been going through its fair share of controversies.
Why is Cloud Seeding Controversial?
The Risk of Contamination
Cloud seeding comes with the risk of contamination that can stem from mishandling silver iodide and other chemicals. They have the potential to set off a chain reaction of environmental pollution, with its harmful consequences taking a toll on our ecosystem and health. The mitigation of these risks requires strategic and structural efforts, which often become financially untenable.
Redistribution of Risk and Not Removal
Cloud seeding is often about moving rain from one location to another. It condenses water that is already present in cloud formations. It could, therefore, imply rain deprivation or drought in one area while externally generated rain in another. It could also become political ammunition to deprive certain regions of water or to claim more water than a specific region requires.
Ecological and Environmental Hazards
Silver iodide-induced bioaccumulation may be potentially harmful to aquatic life. It may also lead to urban flooding.
The scientific community believes that inadequate policymaking has the potential to make cloud seeding harmful. This concern particularly applies when cloud seeding is planned for multiple neighboring regions; in such cases, it has to be conducted according to a well-thought-out schedule. To mitigate risks, there should be limits imposed on when it can be conducted, ensuring there is no risk of flooding.
Lack of Provable Result
Despite being in use for more than 75 years now, cloud seeding lacks enough empirical evidence, especially compared to the volume and scale of studies that have been done on other geoengineering techniques relating to solar energy or carbon removal.
Overall, there is a need to study it holistically. Studies have to go beyond assessing its efficacy by looking not only at its immediate impact but also finding out what cloud seeding may mean to the neighboring regions, their ecology, biodiversity, and more.
Irrespective of the controversies and skepticism surrounding it, one of the foremost purposes of cloud seeding has been to cause rain to cure the earth of pollution, smog, and more. There are commercial enterprises that have taken up the job of curing the earth of these maladies.
Companies With Tested Solutions to Fight Pollution
#1. Tetra Tech
Tetra Tech offers solutions to complex environmental challenges, including solutions relating to air quality enhancement, addressing noise pollution challenges, water quality improvement, solid waste management, and more. If we look at its air quality solutions specifically, they involve computerized databases and reporting software to help clients efficiently and effectively meet their compliance obligations. Services cater to creating emission inventories, dispersion modeling, control technology framework analysis, ambient and emissions monitoring and reporting, and more.
In the fiscal year that ended on October 2nd, 2022, Tetra Tech earned an annual revenue of more than US$3.5 billion, which was an increase from its fiscal year 2021 revenue of over US$3.2 billion. In FY 2022, Tetra Tech reported a net income of more than US$263 million, an increase compared to over US$232 million earned in FY 2021. Tetra Tech shares registered diluted earnings per share of US$4.86 in 2022, compared to US$4.26 in 2021.
Arcadis is another global player that helps organizations better manage air emissions amid climate change, with air pollution being high on the public agenda. It supports clients run according to sustainable business principles across their operations and offers comprehensive industrial hygiene and health & safety services to meet OSHA compliance at industrial facilities.
According to Arcadis' annual integrated report 2022, the company earned more than 3 billion Euros in revenue in 2022, with an operating EBITDA margin (as a percentage of revenues) of 9.8% and 54% return on net working capital. The company earned a revenue of more than 2.5 billion Euros in 2021, with an operating EBITDA margin of 9.6%.
The Future Roadmap for Cloud Seeding
While these large-scale enterprises keep working on ways to keep pollution and environmental hazards away, cloud seeding still stands the chance of emerging as a solution to help the world's most polluted cities. Cloud seeding operations take place in at least eight states across the western United States. These are relatively small-scale operations in terms of the investments involved. Cloud seeding programs in the upper Colorado River Basin, for instance, cost around $1.5 million each year.
Official reports admit that “very little has been documented in determining the impact of small increases in seeded precipitation and increases in seasonal runoff. Because it has been difficult to quantify the seeding impacts, these secondary studies can only be considered speculative.”
Therefore, it is necessary to conduct more studies before we get to know the real efficacy of cloud seeding as a solution to getting rid of pollution.