Wednesday, February 11, 2009

Cloud-Seeding: A Geo-Engineering Tool?

Since its first field-test in 1946 to it’s most recent press exposure during the 2008 Beijing Summer Olympics as a means of pollution control, can cloud-seeding be used to curb global warming?

By: Ringo Bones

As of late, the on-going drought that plagued farmers of Northern and Central china have the Beijing Government yet again resigned their fate to the “somewhat unreliable” technology of cloud-seeding – i.e. artificial rain. The Chinese military – under the unblinking gaze of extensive press coverage – are now using all available means at their disposal to make it rain so that their farmers can have water to irrigate their crops.

Every conceivable method was used from silver iodide / potassium iodide laden anti-aircraft artillery projectiles being fired at rain-bearing clouds to surface-to-air missiles carrying silver iodide / potassium iodide dispensers being flown into rain-bearing clouds in the hopes of creating enough rain for viable farming. Despite of its relative unreliability, can cloud-seeding still be a viable geo-engineering tool to lessen the impact of global warming?

The Bergeron-Findeisen Theory of Rain or the ice-crystal theory of rain has led to our most hopeful attempts to influence the behavior of clouds since primitive man danced his first rain dance. The artificial seeding of rain-clouds – or cloud-seeding – was first developed in 1946 by General Electric’s Vincent J. Schaefer and Irving Langmuir. The principle behind it seems to be a model of logic and simplicity: to introduce into a cloud formation of super-cooled droplets a substance or agent that promotes the formation of ice crystals in which it can fall back to the ground as precipitation or rain.

Two substances proved promising. One was silver iodide (as of late was frequently substituted with the much-cheaper potassium iodide), whose crystalline structure is similar to that of natural ice crystals and therefore provide a hospitable nuclei on which ice crystals can readily form. The other one is solid carbon dioxide - or dry ice – which is so cold that it causes atmospheric water vapor to solidify into enormous numbers of tiny ice crystals. Tiny pellets of dry ice are usually sown into a cloud from airplanes, while silver iodide or potassium iodide is released as smoke, sometimes from an airplane and sometimes from the ground. In both cases, precipitation should follow according to the Bergeron-Findeisen Theory.

Even though our present cloud-seeding efforts either via aircraft dispensing very fine particles of silver iodide / potassium iodide or solid carbon dioxide (dry ice) doesn’t always result in precipitation or rain. Cloud-seeding also has a very promising geo-engineering and weather control potential in slowing down the catastrophic impact of global warming.

The process can help the formation of clouds that can help reflect the incoming infrared spectrum of the solar radiation back out into space. These clouds can be induced to form by seeding cool, moist but cloudless air with very fine silver iodide crystals via dispenser-bearing aircraft. Manufactured clouds like these could also be used to help farmers by preventing the formation of frost over acres of farmland by trapping heat that would otherwise be radiated back out into space. Given these potential benefits, why aren’t cloud-seeding efforts being done more often?

The problem is flying large fleet of aircraft to create the necessary cloud formation needed to lessen the incoming infrared radiation from the Sun also creates a very large carbon footprint in the form of carbon dioxide. The very greenhouse gas we are also minimizing in order to lessen the catastrophic impact of global warming. Though solar-powered / photovoltaic unmanned aircraft are already being tested, these are carbon neutral enough to do the job in the future because there are still too few of them at the present. But who knows what tomorrow might bring even though we are racing against time in lessening the catastrophic impact of global warming and climate change via our yet untested methods of geo-engineering.