Explanation of the Process

• Cloud seeding starts with a chemical. This chemical is usually silver iodine. It has a crystal structure that is similar to water ice. When silver iodine is dispersed into clouds, it causes the water droplets in the clouds to undergo nucleation, which causes supercooling, ice crystal formation and spontaneous development of clouds. This can also be done with other chemicals, such as frozen carbon dioxide, propane and calcium chloride. The chemical is introduced to the atmosphere by aircraft or by projectiles, which shoot the chemical into the sky.
  
  

Pros

• The primary positive result of cloud seeding is that is can potentially produce rain in areas that desperately need water. This result has several positives of its own. Increased rainfall may allow food crops to grow in areas that normally cannot support crops. This can prevent famine in and bring economic prosperity to developing countries. Increased rainfall may also make certain normally dry areas more hospitable for tourists, which is also economically beneficial to these areas.
  
  

Cons

• Several potential drawbacks to cloud seeding exist. Because the process requires placing chemicals in the air, the most immediate concern is how those chemicals will affect the plants and animals below. Silver iodine is not known to cause any serious adverse effects on the health of plants and animals, but several organizations are researching its long-term effects. Also, the cost of cloud seeding is a concern, because it can be very expensive to fly the chemicals and release them into the air. Lastly, controlling the amount of rainfall is a problem because cloud seeding could potentially lead to flooding in some areas.
  
  

Other Information on Cloud Seeding

• Vincent Schaefer, an atmospheric scientist, is credited with inventing the process for cloud seeding in the 1940s, along with contributions from Bernard Vonnegut. Cloud seeding is used heavily in China, to provide water to dry places and to mitigate the large amounts of air pollution in the country. It is also used in the United States to prevent drought, alter harmful weather events during storm seasons and provide snow for ski resorts.