What is cloud seeding?

Cloud seeding is a technique to induce precipitation (rain or snow) by dispersing suitable chemicals into clouds. The result can be encouraging if the clouds targeted contain enough water vapour.

The commonly used chemicals for seeding include silver iodide, potassium iodide, dry ice (solid carbon dioxide), liquid propane and table salt (sodium chloride).

Substances like silver iodide, which has crystalline structure, cause freezing nucleation in clouds. It may also help initiate other microphysical processes in clouds. As a result, tiny water vapour particles grow large and heavy enough to fall as rain drops or snowflakes.

Seeding chemicals may be dispersed by aircraft or from the ground by firing up rockets or similar devices such as anti-aircraft guns. Silver iodide flares can also be released by aircraft flying through clouds.

China has extensively experimented with cloud seeding by firing silver iodide rockets into clouds for induced precipitation and also to clear air pollution.

In India, cloud seeding experiments were conducted a few times to induce artificial rains by the Tamil Nadu government from 1980s. The Karnataka government also attempted similar efforts two decades later. Maharashtra conducted such operations in the beginning of the beginning of the new century. The Delhi government now plans to try the method to combat frequent smog and persistent air pollution.

Some other countries that tried to manipulate precipitation through seeding include Indonesia, Thailand, Kuwait, UAE, USA, Canada, France, Russia, Germany, Australia, and some African countries.

Experts and research show that silver iodide used for cloud seeding may cause negligible health hazards to humans and almost no environmental hazards.

Smog in Delhi, India

Smog has enveloped Delhi in the first week of November 2016. Nothing is visible beyond a few meters in the mornings.

The word smog was coined from smoke and fog to refer to smoky fog. It is highly toxic and can cause serious diseases and even death. It contains oxides of nitrogen, sulphur and carbon, besides ozone, dust, etc. These react with sunlight, moisture, methane, ammonia, etc. to form harmful vapors, and fine particles to form smog.

As the wind speed in Delhi is almost negligent as witnessed in the first week of November 2016, and as the sky is covered by a thick blanket of smog that also hovers over the ground, visibility is reduced to about 100 meters.

The air quality in the city has been become the worst in two decades, taking it to the severe zone. The government of Delhi blames it on crop stubble burning in Punjab and Haryana, road dust and vehicular pollution.

It is estimated that over 600 million tons of agricultural wastes are burnt by farmers during the months of autumn and winter.

Various scientific research reports show that Delhi is the most polluted city in the world and air pollution alone causes about 10,500 deaths annually.

In recent years levels of fine particulate matter (PM) in Delhi increased alarmingly. The city has the highest level of airborne particulate matter, PM2.5, considered the most harmful to health. It has hugely increased the risks of lung cancer and asthma among the residents of Delhi.

The dense smog during winter causes major air and rail traffic disruptions too.

Since the 1990s, Delhi has undertaken several measures to reduce air pollution and smog. The city has the third highest number of trees among all Indian cities. The DTC runs largest fleet of environment-friendly CNG buses in the world. The Supreme Court of India ordered the conversion of the city’s buses and taxis to run on CNG and banned leaded petrol since 1998. The Delhi Metro Rail has helped significantly to reduce air pollutants.

But these gains have become insignificant due to large scale crop stubble burning, rise in the number of diesel automobiles, and similar harmful factors.

Delhi’s population is now estimated to be about 25 million, second only to Tokyo with about 38 million. That means the government has to enact strict rules immediately and implement them with an iron fist.