National Science Foundation: Special Commission On W.M. - Weather and Climate Modificaton (1965)

 

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Twenty years ago General Electric Company scientists Irving Langmuir and Vincent Schaefer modified clouds by "seeding" them with dry ice pellets. Not long afterward Bernard Vonnegut, a co-worker, demonstrated that a smoke of silver iodide crystals would accomplish the same result. This was the beginning of the modern American history of weather and climate modification through cloud seeding. These American scientists on November 13, 1946, had verified experimentally the theory advanced in 1933 by the Swedish meteorologist, Tor Bergeron, and the German physicist, Walter Findeisen, that clouds would precipitate if they contained the right mixture of ice crystals and supercooled water drops. The Bergeron-Findeisen theory was antedated by the work of the Dutch scientist, August Veraart. The enthusiastic reports by Veraart of his 1930 experiments with dry ice and supercooled water-ice in Holland were not well received by the Dutch scientific community, and thus were given no serious consideration elsewhere. Weather and climate modification, or "rainmaking" (the more popular and also more restricted concept), is not new to our era or to our country. Many traditional societies, including the American Indians, have practiced some type of religious or ritualistic rainmaking. The ceremonials and rituals have varied from dousing holy men with water to burying children up to their necks in the ground in the hope that the gods would be sympathetic and drop tears from the heav ens. These ceremonies are not only to induce some form of desirable weather but also to reinforce the tribal religious beliefs and opinions which maintain social unity. Through ancient and modern times many methods have been proposed and attempted to induce or to aid rainfall. Two U. S. Government patents on methods of rainmaking were issued before the turn of the 20th century based, respectively, upon the production of carbon dioxide by expending "liquified carbonic acid gas" and upon concussion by the detonation of explosives. Interestingly enough the long since expired patent, based on the production of carbon dioxide in the form of dry ice, anticipated the cloud seeders of today.