New Delhi wants to seed clouds to bring rain and drive away the toxic fog that suffocates it every fall, a controversial technique that environmentalists say does not address the root causes of the problem.
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The municipalities’ idea is to spray common salt or a salt mixture into the clouds to trigger condensation in the form of rain.
“Even very moderate rainfall is effective in reducing environmental pollution,” says Sachchida Nand Tripathi, professor of sustainable energy engineering at the Indian Institute of Technology (IIT) in Kanpur (North), who initiated the project.
The megalopolis of 30 million people is regularly ranked as the world’s most polluted capital, with levels of PM2.5 – microparticles that enter the blood system through the lungs – regularly more than 30 times higher than the organization’s limits . World Health Organization (WHO). ).
But breathing in toxic air has catastrophic health consequences. According to the WHO, prolonged exposure can trigger strokes, heart disease, lung cancer and respiratory diseases.
A New Delhi resident loses an average of 12 years of life due to air pollution, according to a study published in August by the Energy Policy Institute at the University of Chicago.
During recent air pollution spikes, authorities had to temporarily close schools in the capital, ban construction sites and ban diesel vehicles.
Unnecessary effort?
However, since these measures had no effect, the government asked the Kanpur Institute of Technology to prepare for cloud seeding by plane or cannon.
According to Mr. Tripathi, this technique is effective and “has shown no ill effects wherever it has been tried.”
But the high price and doubts about the effectiveness of the method make observers frown.
Although the exact cost has not been published, Indian media reports a sum of 10 million rupees (about 120,000 dollars or 110,000 euros) for an area of 100 square kilometers.
For environmental expert Bhavreen Kandhari, this is an “ineffective approach” to combat pollution. “We risk spending public money unnecessarily and wasting valuable time,” she told AFP.
Pollution in New Delhi is caused by a mix of factory and vehicle exhaust, compounded by seasonal fires set by farmers in surrounding areas.
The phenomenon becomes even worse in autumn and winter, when colder air traps pollutants. Residents of the capital are therefore advised to wear masks at all times outdoors.
“Ephemeral respite”
India is not the first country to use this technique.
China regularly spends billions of dollars to change weather patterns to protect agricultural regions or improve air quality before major events.
Scientists in western India have also successfully tested it, achieving a 20% increase in rainfall, says Mr Tripathi.
However, Sunil Dahiya, an analyst at the Center for Research on Energy and Clean Air (CREA), believes that artificial rain is not a “final solution” to pollution.
“The respite is only short-lived, because as soon as the rain stops, polluted air masses arrive, which quickly reduce the air quality to a dangerous level.” Emissions must be reduced at the source “in order to sustainably and significantly improve air quality,” emphasizes the expert.
Professor Tripathi said cloud seeding was “worth a try”, particularly as other measures had failed.
Two years ago, New Delhi tried another experiment: a “smog tower,” a giant fan designed to suck in and purify the air. But this structure, which cost around two million dollars (1.8 million euros), only worked within a radius of 50 meters and was abandoned.