As Delhi’s air quality slipped once again into the ‘very poor’ category, the city government on Tuesday turned to a long-debated idea to clean the air — cloud seeding.
The exercise, carried out in collaboration with the Indian Institute of Technology (IIT) Kanpur, was Delhi’s first cloud-seeding attempt in over five decades. Aircraft flew over Burari, Mayur Vihar, Karol Bagh and Badli in an effort to trigger rain clouds that could wash away pollutants.
Despite the anticipation, the India Meteorological Department (IMD) confirmed that no measurable rainfall occurred in Delhi. Only traces were recorded — 0.1 mm in Noida and 0.2 mm in Greater Noida.
Government calls it a scientific step
Delhi’s Environment Minister Manjinder Singh Sirsa, who supervised the operation, called it a “scientific step” in the fight against pollution.
“This is a huge step taken by the government to mitigate pollution. If these trials are successful, we will prepare a long-term plan till February,” Sirsa said. He described it as “a first-of-its-kind scientific effort to clean Delhi’s air.”
Sirsa added that this was not a one-off experiment but part of a broader plan that could lead to regular cloud-seeding operations if results prove encouraging.
A government report noted that particulate matter levels temporarily dropped in the trial areas. “Before cloud seeding, the PM2.5 level was 221 in Mayur Vihar, 230 in Karol Bagh and 229 in Burari. After the first seeding, they reduced to 207, 206 and 203, respectively,” it said. PM10 levels fell from 209 to 177 in Burari and from 206 to 163 in Karol Bagh.
Officials clarified that humidity during the trials was only 15–20%, far below the ideal 50% needed for effective seeding. “Rain could occur within 15 minutes to four hours of the operation, depending on moisture and temperature,” the minister said.
Each Cessna aircraft carried eight silver iodide and sodium chloride flares, weighing between 2 and 2.5 kilograms, released from altitudes of 4,000 to 6,000 feet. The flares were fired for around 17 minutes each, in hopes that microscopic silver particles would trigger condensation and rainfall.
Two trials were carried out on October 28— one at 2 PM and another at 4 PM — coordinated between Delhi and Meerut airspace. Officials said nine to ten more trials are planned over the next few days, focusing on northern Delhi, where wind direction is expected to be favourable.
Revival after five decades
This was the capital’s third recorded cloud-seeding effort. Climate scientist Roxy Mathew Koll from the Indian Institute of Tropical Meteorology (IITM) said the first trial took place in 1957, followed by another in the early 1970s.
In those early experiments, silver iodide was released from ground-based generators to encourage raindrop formation. Both attempts failed due to low humidity and weak cloud systems — the same conditions now hampering Delhi’s efforts.
This history has led many experts to question whether the latest experiment, though more data-driven, was scientifically justified given the current weather.
Weather too dry for results
Meteorologists stress that cloud seeding cannot create rain from clear skies. It requires existing clouds with enough moisture and favourable temperature profiles for condensation.
“Cloud seeding can only work when clouds are already present; it cannot generate rain from clear skies,” said a senior IMD scientist, requesting anonymity. “Delhi’s atmosphere between October and December is typically too dry for such operations. Low humidity, weak convection and stagnant winds limit the potential success rate.”
IMD data showed moisture content at only 10–15% during the trial — far below the required threshold.
Similar challenges have hindered other countries. Pakistan cancelled a planned operation in Rawalpindi and Islamabad in early 2024 due to a lack of clouds. Even in China, where cloud seeding is common, operations are usually conducted in humid months when a cloud base already exists.
“No technology, however advanced, can overcome nature’s basic requirement. You cannot make rain without clouds,” the IMD scientist said.
A short-lived and costly fix
Even when conditions are ideal, cloud seeding has only a modest and short-lived impact. Studies worldwide, including Israel’s six-decade experiment, show that rainfall typically increases by just 1–2% and lasts only a few hours.
Israel, once a global pioneer in weather modification, discontinued its national programme in 2021, concluding that the benefits were negligible compared to the costs.
In Delhi, each round of cloud seeding costs about Rs 3.21 crore, including Rs 2.75 crore for the trials (Rs 55 lakh per round) and Rs 66 lakh for calibration, logistics and support.
“Even if successful, artificial rain would only temporarily suppress dust and pollutants, which would resurface within hours once vehicles hit the roads again,” said a senior IIT Delhi professor involved in air-quality monitoring.
Environmental activist Bhavreen Kandhari called it another “band-aid” measure. “The impact of cloud seeding will fade within hours, which is a complete waste of public money. It’s like the smog towers — high-cost experiments that make for good optics but fail to address the root problem,” she said.
The Delhi Pollution Control Committee (DPCC) has also warned that short-term measures like artificial rain do little to address deeper, long-term pollution sources such as industrial emissions, construction dust and vehicular exhaust.
Silver iodide under scrutiny
The main chemical used in seeding — silver iodide (AgI) — has long raised environmental concerns. The U.S. Environmental Protection Agency (EPA) classifies it as a hazardous substance that can persist in soil and water, harm aquatic life and enter the food chain.
Pushkar Pawar, a town planner with the Municipal Corporation of Delhi (MCD), warned that “while silver iodide is effective in forming condensation nuclei, it remains toxic in large quantities.”
“Repeated use could lead to accumulation in soil and water bodies, degrading soil quality, harming aquatic ecosystems and affecting biodiversity,” he said. “Chronic exposure to silver can cause respiratory problems, skin irritation and, in rare cases, a condition called argyria — where the skin turns bluish-grey due to silver buildup in tissues.”
Several countries have reported side effects from large-scale seeding. In China’s Hunan province, post-operation soil tests found trace contamination from silver residues. In Russia, similar experiments reduced soil fertility in certain regions.
Kandhari said such risks make Delhi’s move even more questionable. “The environmental footprint of silver iodide could linger far longer than its impact. Adding more chemicals to a city already burdened with toxic air and water is the last thing we need.”
Unpredictable skies and safety concerns
Weather modification is inherently unpredictable. Small changes in temperature, wind direction or cloud structure can cause disproportionate results, including excessive rainfall or localised flooding.
In 2009, a cloud-seeding operation in Henan, China, unexpectedly intensified and caused flash floods that displaced hundreds. In Thailand in 2011, artificial rain trials worsened flooding in nearby provinces.
Given Delhi’s chronic waterlogging problems, such scenarios raise valid safety concerns. The city’s clogged drains, dense sprawl and low-lying settlements could worsen any unexpected downpour.
“Who will be responsible if artificial rain causes excessive rainfall or flooding?” asked a senior environmental scientist from IIT Kanpur. He noted that India currently has no legal framework defining liability for weather-modification outcomes.
Kandhari added, “Before turning to such costly and uncertain interventions, we must ask who will bear responsibility if artificial rain leads to unintended consequences. The focus should remain on tackling real pollution sources — vehicles, industries and construction dust — since only addressing these can deliver lasting clean air.”
Politics and public perception
While the Aam Aadmi Party (AAP) mocked the exercise as a “publicity stunt”, joking that the government was trying to “steal Lord Indra’s credit”, the BJP defended it as a “bold and innovative step”.
A government official from the Environment Department countered the criticism, saying, “The goal is to explore every possible scientific tool. No one claims this is a silver bullet, but we need to test and verify how such interventions perform in Indian conditions before rejecting them.”
Fixing what lies on the ground
Experts agree that Delhi’s pollution crisis cannot be solved by looking skyward. The city’s toxic air stems mainly from ground-level emissions — vehicular exhaust, industrial discharge, construction dust and crop residue burning in neighbouring states.
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Redirecting funds from costly sky experiments to public transport, stricter emission control and renewable energy could yield more lasting results.
“We keep looking upward for solutions — drones, rain, clouds — when the real problem lies on the ground,” said Kandhari. “Pollution will not vanish until we change how we move, build and breathe.”
Looking ahead
Despite scepticism, officials say the ongoing trials will continue. Data from each flight will be analysed jointly by IIT Kanpur and the DPCC, and a detailed report is expected next month.
Sirsa said the government would take a “science-based decision” on whether to expand the operation. “We are not doing this blindly. Every result will be scientifically validated. If this helps even marginally in bringing down particulate levels, we will refine and scale it,” he said.
Yet, with Delhi’s Air Quality Index hovering above 350 in many areas — triggering Stage II of the Graded Response Action Plan (GRAP) — critics argue that the city’s focus should be on immediate emission control, not experimental fixes.
