Authorities in Indian capital Delhi unsuccessfully carried out a cloud seeding trial, which is the science of altering clouds to make rains, to tackle the city’s worsening air pollution on Tuesday. <\/p>\n
Cloud seeding is done by firing small particles – usually silver iodide – into clouds to produce rain. The technique is used around the world, but experts doubt its efficacy as a long-term air pollution control measure.<\/p>\n
A team of the Indian Institute of Technology (IIT) Kanpur and the Delhi government carried out the trial over several neighbourhoods, as thick smog enveloped the city. <\/p>\n
But the attempt – the first in 53 years – was “not completely successful” due to the lack of moisture in the air.<\/p>\n
Over the past two weeks, Delhi’s Air Quality Index (AQI) – which measures the level of PM 2.5 or fine particulate matter in the air that can clog lungs – has been hovering between 300 and 400, which is nearly 20 times the acceptable limit.<\/p>\n
On Tuesday, authorities used a Cessna aircraft to release fire flares containing silver iodide and sodium chloride into the atmosphere.<\/p>\n
In a statement, IIT Kanpur said that despite the lack of rain, there had been a measurable reduction in particulate matter because of Tuesday’s experiment, “indicating that even under limited moisture conditions, cloud seeding can contribute to improved air quality”. <\/p>\n
However, the institute’s director Manindra Agarwal told BBC Hindi that this can’t be a long-term fix for Delhi’s perennial pollution problem. <\/p>\n
“One measure of success is if it rains, which certainly did not happen,” said Mr Agarwal. “The moisture content in the clouds yesterday [Tuesday] was very low. We will continue our efforts in the near future.”<\/p>\n
The trial is likely to be repeated in the coming weeks after the moisture levels in the clouds increases again, Delhi’s Environment Minister Manjinder Sirsa told reporters. <\/p>\n
Delhi’s first cloud-seeding experiment was carried out in 1957, followed by another attempt in 1972, according to the Indian Institute of Tropical Meteorology<\/a>. <\/p>\n While those experiments were aimed at drought management, this was the first indigenous effort at cloud seeding to control pollution, said Mr Agarwal. <\/p>\n The city had considered cloud seeding in 2023<\/a> as well, but the plan did not materialise due to pending court approvals. <\/p>\n Back then, scientists had also highlighted how it was an expensive strategy with low success rates. <\/p>\n Cloud seeding speeds up the condensation of moisture in clouds to create rain. The salt granules act as ice-nucleating particles, which enable ice crystals to form in the clouds. The moisture in the clouds then latches on to these ice crystals and condenses into rain.<\/p>\n But the process doesn’t always work and is dependent on the right amount of moisture and humidity in the clouds to allow for ice nuclei to form.<\/p>\n There is not enough empirical evidence on how much the AQI can come down by cloud seeding, climate change and sustainability expert Abinash Mohanty told the BBC in 2023. <\/p>\n “We also don’t know what its [cloud seeding] effects are because in the end you’re trying to alter natural processes and that’s bound to have limitations.”<\/p>\n Globally cloud seeding exercises have yielded mixed results.<\/p>\n China has boasted about its success to manage rains before hosting the Olympics<\/a>, with Beijing using rockets, cannons and drones to do cloud seeding. <\/p>\n However, in the United Arab Emirates, questions over the technique were raised, following floods in Dubai<\/a> last year.<\/p>\n Follow BBC News India on Instagram<\/a>, YouTube,<\/a> Twitter<\/a> and Facebook<\/a>.<\/p>\n