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Project Cirrus and Hurricane King’s Sudden Turn
In October 1947, Project Cirrus dropped crushed dry ice into Hurricane King as it moved away from Florida. The storm then reversed course and struck near Savannah, Georgia. Residents and officials blamed the experiment, but later meteorological analysis found that comparable unseeded storms had followed similar turns. The episode did not prove that seeding redirected the hurricane, but it created public and legal alarm that delayed further hurricane-seeding experiments.
A cloud-physics project reaches a hurricane
On 13 October 1947, Project Cirrus aircraft seeded Hurricane King’s outer clouds with roughly 180–190 pounds of dry ice. The storm was moving away from Florida over the Atlantic, which made it seem a comparatively safe experiment. NOAA’s history describes three aircraft: one to release material, another to observe and a control aircraft carrying Vincent Schaefer. They avoided the eye and heaviest rainbands.[1]
The size of the proposed effect
Cirrus brought together General Electric, the Naval Research Laboratory and the Army Signal Corps. Schaefer’s 1946 demonstration that dry ice could freeze supercooled droplets had encouraged cloud experiments. But changing droplets in a cloud and changing the track of an entire cyclone were different propositions. Observed changes below an aircraft could not establish control over the storm’s movement.[1][2]
Why sequence did not establish causation
King turned west and struck near Savannah on 15 October. NOAA records one death and about $2 million in contemporary damage. Threatened litigation followed; General Electric’s Irving Langmuir expressed strong confidence that seeding had caused the turn. Meteorologists investigating for the Weather Bureau identified comparable natural tracks, and later reviews note that King’s movement had begun changing before the flight.[1][2][3]
The missing comparison was an otherwise identical unseeded storm. A control aircraft could observe the experiment, but it could not supply that counterfactual hurricane. Earlier storms and the timing of the turn weakened the claim that dry ice caused the landfall without denying that a seeding flight occurred.[1][2][3]
What later experiments had to distinguish
Later Project STORMFURY used silver iodide and sought lower wind speeds, rather than a redirected track. Its scientific review found that natural hurricane changes could imitate the expected experimental response. Across the two programmes, the recurring problem was identifying a distinct effect of intervention in a system already changing on its own.[4]
Supporting sources
Primary & research sources. Numbered references connect claims to the sources below; disputed details are identified in the text.
- 70th Anniversary of the First Hurricane Seeding ExperimentNOAA Atlantic Oceanographic and Meteorological Laboratory / Institutional
NOAA history documents the flight, dry ice, landfall and controversy; does not attribute the track reversal to seeding.
- Climate Intervention: Reflecting Sunlight to Cool Earth, Appendix C: Planned Weather ModificationNational Academies of Sciences, Engineering, and Medicine / Reference
National Academies history places the experiment within weather-modification research and describes the difficulty of causal attribution.
- Historical Review of Research Activities toward Typhoons/Hurricanes Modification in Japan and the United StatesJournal of the Meteorological Society of Japan / Academic
Academic review examines hurricane modification and natural changes; later synthesis does not provide an experimental control for King.
- Project STORMFURY: A Scientific Chronicle 1962–1983Bulletin of the American Meteorological Society / Academic
Scientific review of Project STORMFURY explains physical and observational limitations of hurricane modification; later program used a different agent and objective.
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Archive image credit
Project Cirrus crew and scientists standing in front of a B-17 used for the 1947 hurricane-seeding flight.. U.S. Navy. Public domain (U.S. government work). Resized and cropped for the archive card.