As the Indian capital grapples with an alarming surge in toxic air, the Delhi government is contemplating the use of cloud seeding—a rain-making technique—to mitigate pollution levels. The potential implementation of this strategy hinges on securing approval from India’s Supreme Court and various federal ministries, with a tentative timeline set for later this month, dependent on favorable weather conditions.
The proposal to employ cloud seeding as a remedy for Delhi’s air pollution is not novel, but skepticism surrounds its effectiveness. Experts argue that this complex and costly process lacks conclusive evidence of its efficacy in combating pollution, emphasizing the need for further research to discern its long-term environmental impact.
The recent escalation of pollution in Delhi, as reflected in the Air Quality Index (AQI), has sparked renewed urgency. Over the past two weeks, the AQI consistently surpassed the 450 mark, nearly ten times the acceptable limit. Despite a temporary respite from natural rainfall over the weekend, air quality deteriorated again on Monday due to Diwali celebrations involving firecrackers.
Delhi’s air quality woes persist throughout the year, driven by factors such as high vehicular and industrial emissions, as well as dust. The situation exacerbates in winter when crop residue burning by farmers in neighboring states and low wind speeds lead to heightened pollutant concentrations. In response, the Delhi government has declared early school winter breaks, imposed a ban on construction activities, and is now pinning its hopes on Supreme Court approval for cloud seeding.
Understanding Cloud Seeding:
Cloud seeding is a technique designed to accelerate the condensation of moisture in clouds, inducing rain. It involves spraying particles of salt, such as silver iodide or chloride, onto clouds using aircraft or ground-based dispersion devices. These salt particles act as ice-nucleating agents, facilitating the formation of ice crystals in the clouds. Moisture then adheres to these ice crystals, ultimately condensing into rain.
The success of cloud seeding, however, is contingent on precise atmospheric conditions. Polash Mukerjee, an independent researcher on air quality and health, underscores the importance of optimal moisture, humidity, and dynamic wind speeds in the clouds. Additionally, the choice of cloud type is crucial, with weather scientist JR Kulkarni noting that vertical growth is preferable over horizontal expansion.
Cloud seeding is not a recent innovation; climatologist SK Banerji, the first Indian director general of the meteorological department, experimented with it as early as 1952. In the 1960s, the US military controversially utilized the technique to manipulate the monsoon in certain areas of Vietnam during the war. Various countries, including China, the UAE, and certain Indian states, have explored cloud seeding to enhance rainfall or address drought conditions.
The Delhi Government’s Plan:
The cloud seeding project proposal originates from researchers at the Indian Institute of Technology (IIT) Kanpur, a leading engineering institution. The two-phase project, covering approximately 300 square kilometers, is slated to commence in late November if approved. Meteorological conditions on the suggested dates of November 20 and 21 are deemed favorable for implementation, according to Manindra Agrawal, the scientist leading the project.
Agrawal acknowledged that full cloud coverage over Delhi might not be achievable, but emphasized that a few hundred kilometers would be beneficial. The underlying rationale is that rainfall could potentially wash away particulate matter in the atmosphere, resulting in cleaner and more breathable air.
Debating the Efficacy of Cloud Seeding:
While Delhi experienced a reduction in pollution levels after natural rainfall last week, experts remain uncertain about the effectiveness of artificial rain generated through cloud seeding. Mukerjee argues that while rainfall immediately lowers pollution levels, the impact is transient, with pollution rebounding within 48-72 hours. He deems cloud seeding an expensive, short-term solution that diverts scarce resources.
Mukerjee stresses the necessity for a well-deliberated policy, involving a multidisciplinary team comprising meteorologists, air quality policy experts, epidemiologists, and more. Abinash Mohanty, a climate change and sustainability expert, echoes these sentiments, expressing concern about the lack of empirical evidence regarding the AQI reduction achievable through cloud seeding.
Mohanty underscores that addressing pollution requires concerted efforts beyond meteorological variables, advocating for comprehensive strategies rather than scattered trial-and-error experiments. He highlights the inherent limitations of altering natural processes through cloud seeding, emphasizing the need for a more thorough understanding of its potential effects.
The proposal to employ cloud seeding as a solution to Delhi’s persistent air pollution crisis is met with both anticipation and skepticism. As the Delhi government awaits the Supreme Court’s decision, the efficacy and long-term impact of cloud seeding remain subjects of debate among experts, emphasizing the ongoing challenges in combating the city’s hazardous air quality.