WEATHER MODIFICATION—A SCENARIO FOR THE FUTURE
BY ROLAND LIST
AMERICAN METEOROLOGICAL SOCIETY JANUARY 2004
"Weather modification can be substantially improved by a better understanding of the precipitation processes and by more refined methods and technologies."
EVOLUTION AND ACHIEVEMENTS IN WEATHER MODIFICATION
Modern weather modification (WM) started with Langmuir and Schaefer in 1948 (Schaefer 1953) who used dry ice pellets to produce holes in supercooled stratus by snow-out.
This experiment was a very convincing, visual proof that seeding works; it encouraged new rain enhancement and hail prevention projects all over the world.
The euphoria about humanity’s unlimited expectation to change the weather is reflected in a speech by President John F. Kennedy given in 1961 to the United Nations in which he stated the following in the section on the exploration of the universe and the peaceful use of space:
(associated image from JFK library)
“We shall propose further cooperative efforts between all nations in weather prediction and eventually weather control.”
Note that he did not say “weather modification;” he foresaw the time when weather could be controlled, that is, pressing a button at two o’clock in the morning and getting rain at five o’clock.
Why has weather modification gone downhill since then and why has it received such a bad reputation?
The blunt answer is that it has not delivered as expected.
What WM can and cannot do is summarized in the periodically updated Statement of the Art of Weather Modification by the World Meteorological Organization.
The American Meteorological Society has issued a similar assessment.
WMO has also issued guidelines for planning weather modification experiments .
In these statements success is listed for dissolution of warm and supercooled fog, supercooled stratus decks, and, to a limited extent, for cold and warm rain enhancement.
No successful randomized experiments have been reported on snowpack augmentation, hail and tornado prevention, or the moderation of floods and tropical cyclones (hurricanes and typhoons).
The reduction of winds in hurricanes was once reported in the WMO statement as a result of silver iodide (AgI) seeding (e.g., WMO 1976).
However, that claim was later removed at the request of the United States.
In summary, the modification possibilities are quite limited for the economically most important cases: rain and severe storms.