Cloud-seeding is a scientific technique aimed at artificially inducing rainfall by dispersing
certain substances into clouds. According to Dr. Thara Prabhakaran, Scientist G at IITM Pune,
cloud formation and precipitation depend on several factors such as moisture availability,
aerosols, and anthropogenic emissions. For successful cloud-seeding, there must be existing
clouds with sufficient moisture content and suitable physical conditions. Hence, only a specific
type of cloud structure can be effectively seeded, making the process complex and uncertain.

Findings from IITM Pune Research

The Indian Institute of Tropical Meteorology (IITM) conducted detailed research under its
CAIPEEX (Cloud Aerosol Interaction and Precipitation Enhancement Experiment) program to
evaluate cloud-seeding efficiency. Through randomized trials, IITM found that seeded clouds
showed up to 80% enhancement in rainfall compared to unseeded ones and also lasted longer.
The study revealed that hygroscopic aerosols like salts promote rainfall by absorbing water
vapour, whereas hydrophobic aerosols such as black soot hinder cloud formation. This
highlights the importance of identifying the right kind of clouds and seeding materials, as not all
clouds respond favorably.

Cloud-Seeding for Pollution Control

Using cloud-seeding to control pollution, as attempted in Delhi, is an entirely different and
uncertain process compared to inducing rainfall. The atmosphere already contains numerous
aerosols, and the interaction between these particles and seeding agents is not fully understood.
Dr. Prabhakaran emphasizes that more systematic research and documentation are required
before cloud-seeding can be used as an effective pollution control method. Operational use
should only begin after determining the most suitable atmospheric conditions and cloud types. 

Environmental and Safety Concerns

While sodium chloride (common salt) is often used for warm clouds, silver iodide, used in some
seeding experiments, is toxic to aquatic life even in minute quantities. Studies in the United
States have found traces of silver near seeding sites, raising concerns about its environmental
impact. In India, long-term ecological studies on cloud-seeding effects are lacking, and scientists
urge caution until such data is available. Therefore, understanding the environmental safety of
cloud-seeding is as essential as studying its rainfall potential.

Anthropogenic Emissions and Atmospheric Effects

Anthropogenic emissions, including pollutants from vehicles, industries, and biomass burning,
release large quantities of particulates into the atmosphere. These can suppress cloud formation
and alter rainfall patterns. Dr. Prabhakaran stresses the need for collective environmental
responsibility, noting that atmospheric cleaning requires coordinated efforts from citizens,
policymakers, and scientists. Cloud-seeding alone cannot solve environmental or climatic
challenges; it must be integrated into a broader strategy for pollution mitigation and sustainable
development. 

UPSC Relevance

This topic is important for GS Paper 1 (Geography) and GS Paper 3 (Environment &
Science). It covers weather modification, pollution control, and environmental ethics.
Key Concepts: Cloud-se