Cloud Seeding: The Modern Rainmaker
Since time began, the fate of civilizations has hinged on the weather. From flood to famine, our lives have been determined by when it rains, when it becomes cold, and the important spring thaw. Modern science has come up with a plan to tip the scales in our favor. It is called cloud seeding and is an ingenious way to convincing Mother Nature to give us just the precipitation we’re looking for.
How does it work?
Cloud seeding works on a complex principle. A “seed” is a cloud condensation nucleus. These particles are actually little bits of solid ice for water vapor to turn into actual water. It’s like breathing on a cold window: the breath turns to water and can be manipulated. A cloud seed is like a giant cold window with water vapor all around. This is a natural phenomenon and is part of the larger picture of how rain develops.
The process of deliberate cloud seeding builds on this premise. Silver iodide and frozen carbon dioxide (a.k.a. dry ice) are two chemicals commonly inserted into clouds to produce water vapor and eventually rain. To make the cold, the silver iodide is inserted and quickly brings the temperature of the cloud to below freezing. This starts the first chain of the process. The water vapor then returns to its aqueous state until there is enough water to fall as rain. Dry ice, by contrast, actually cools the cloud to a point that the cold vapor turns immediately to water without the need of a seed.
Different strategies are used at different geographical locations. Around areas north and south of the equator, the seeds actually become so heavy with ice that they fall as snow. Of course, should the season be warm, these particles will melt before they near the ground and rain is created. In the tropics, the same methods are used, but the inherent heat of the atmosphere quickly melts the seeds. This causes rain.
Planes must fly through properly selected clouds and release the chemicals via flare. Even some on ground generators exist, utilizing the wind currents to pull the chemical into the cloud.
What are the disadvantages?
Some critics of the method claim that cloud seeding does not do anything more for the land then a simple storm cloud would. There is no way to tell how many inches of rain any particular cloud would produce. For this reason, it is difficult to determine the effectiveness of cloud seeding. Also, only particular clouds will do. Not all clouds are a candidate for seeding. Altitude, cloud type, and surface weather must be taken into consideration.
There are also questions as to the relative safety of this method to all who exist below seeded clouds. Research is currently underway to determine if silver iodide could be toxic to humans and the environment with long term exposure. In addition, some question the ethics of cloud seeding. It can be used to stop rain as well as initiate it and could upset the balance of the ecosystem for our personal benefit.
It is very tempting to change the weather to suit our needs, but more research must be done to determine if the method is safe. We only have one world. If it is abused in our need to accumulate more food, more water, and more rain, we run the risk of losing the battle altogether. Cloud seeding, though a fascinating concept with far reaching possibilities, should be used with caution until all of the pertinent facts are known.