Mint Explainer: Why cloud seeding is easy to propose but hard to implement

IIT-Kanpur has been working on cloud seeding for over five years but the technology is yet to go mainstream (Photo: Hindustan Times)
IIT-Kanpur has been working on cloud seeding for over five years but the technology is yet to go mainstream (Photo: Hindustan Times)

Summary

  • Many countries use this technology, including India and China, but implementing it is far from straightforward and risks damaging the environment

On Wednesday the Delhi government said it would attempt to induce artificial rain through cloud seeding in a bid to tackle the city's worsening air pollution. It has asked a team of scientists from the Indian Institute of Technology (IIT) at Kanpur to prepare a proposal for cloud seeding, which will be submitted to the Supreme Court for approval.

Cloud seeding to produce artificial rain is not new. It was first used by the late Vincent Joseph Schaefer, an American chemist and meteorologist, in November 1947, when he flew over Mount Greylock in Massachusetts in a plane and successfully seeded clouds with pellets of dry ice (solid carbon dioxide) to produce the first artificial snowstorm. This was among his first field experiments, following his work a year earlier at the General Electric Laboratory in Schenectady, New York. 

In India, a paper titled 'Cloud Seeding Experiment using Common Salt' was published in January 1967 in the Journal of Applied Meteorology. According to the paper, "an experiment on artificial stimulation of rain using a warm cloud seeding technique was undertaken in three nearby climatologically similar regions, Delhi, Agra and Jaipur in northwest India".

Many countries now use this technology, including India and China, but implementation is easier said than done. It has certain limitations, not to mention a likely adverse impact on the environment.

IIT-Kanpur has been working on cloud seeding for over five years but the technology is yet to go mainstream. The institute successfully conducted a test flight (with a Cessna aircraft) for cloud seeding on 22 June. However, it was raining that day, and "the intent was to check the systems and collect data, not to seed the cloud and make it rain", according to an article in Vox Populi.

Cloud seeding involves the introduction of certain substances into the atmosphere such as silver iodide, potassium iodide, or even liquid propane (which expands into a gas), that act as a core around which water vapour can condense, forming droplets or ice crystals. As these particles combine and grow bigger, they eventually fall to the earth as rain or snow. 

Techniques include silver iodide seeding, which involves dispersing silver iodide into clouds, promoting the formation of ice crystals. Potassium iodide and potassium chloride seeding similarly encourages ice-crystal formation in clouds. Silver iodide, which the Chinese use, is effective because its form is similar to that of ice crystals. Calcium chloride is often used in warmer regions, and researchers have also used sodium chloride (common salt) for cloud seeding. 

Other techniques involve hygroscopic flares that contain materials which introduce moisture into clouds. Carbon-dioxide seeding makes use of solid carbon dioxide, or dry ice, to cool the air and stimulate the formation of ice crystals. In acoustic cloud seeding, specialised aircraft emit soundwaves to encourage cloud droplets to coalesce. Electrically charged particles can also be used to influence charged-particle distribution in clouds and potentially promote precipitation.

Cloud seeding is commonly used in places where water is scarce. However, its effectiveness depends on various factors such as cloud type, atmospheric conditions, and the method used. For instance, according to a 28 December 2021 article in the Times of India, a document from the Central Pollution Control Board obtained through the Right to Information (RTI) Act, revealed that weather conditions such as low moisture in New Delhi during the winter are "unsupportive of cloud seeding", following which the project was abandoned.

Several countries have successfully used cloud seeding techniques. The US has implemented cloud-seeding programs in states such as California, Texas and Colorado. China, known for having one of the world’s most extensive cloud-seeding programs, uses various techniques to alleviate water scarcity. Russia has also used cloud seeding, notably for events such as the Moscow Victory Day Parade. The UAE also invests in cloud seeding technology to combat water shortages. Australia has conducted cloud-seeding operations in various states to increase rainfall in drought-affected areas. Israel and Thailand have used cloud seeding to augment water resources and address drought challenges. Indonesia, too, has explored cloud seeding methods to boost rainfall, particularly in agricultural regions.

The global cloud-seeding market was valued at $120.2 million in 2021 and is expected to be worth about $189 million by 2030, according to Polaris Market Research. It helps alleviate the impact of droughts, assists in the effective management of water reservoirs, and reduces the risk of wildfires in dry regions. 

Cloud seeding also has the potential to improve air quality by washing away particulate matter and pollutants from the atmosphere with precipitation, which explains why New Delhi is keen on implementing the technology. Moreover, it can augment snowpack in mountainous areas, acting as a natural reservoir that gradually releases water during the warmer months. This snowpack enhancement is vital for downstream water supply and management. Cloud-seeding experiments also provide valuable data for weather-modification research, enhancing our understanding of weather patterns, cloud behavior and atmospheric processes.

That being said, a major concern is the environmental impact of cloud seeding, as manipulating precipitation patterns could disrupt natural ecosystems and create imbalances in plant and animal habitats. There are also concerns about unintended consequences such as altered wind patterns and unexpected weather events in nearby regions.

There are also ethical considerations regarding human intervention in natural processes, raising questions about the rights of different communities to natural resources. Additionally, artificial rain may lead to water-quality issues by driving pollutants from the atmosphere into water bodies.

Another challenge is the limited effectiveness of cloud seeding. Its success depends on various factors and is not guaranteed. Cloud-seeding programs also require substantial and costly resources, including aircraft, seeding materials and skilled personnel. Legal and regulatory challenges, such as issues related to water rights and environmental impact, often arise around cloud-seeding activities.

Cloud seeding could also be used as a "weapon". According to a 3 July, 1972 article in The New York Times, "The United States has been secretly seeding clouds over North Vietnam, Laos and South Vietnam to increase and control the rainfall for military purposes".

Considering these factors, a careful and comprehensive approach that includes thorough environmental and ethical assessments, is necessary when contemplating cloud-seeding initiatives.

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