Might there be some way to weaken hurricanes, so that they pose less of a danger to life and property?
Scientists have long speculated about this possibility. Occasionally they’ve even had a chance to test some of their ideas.
The first significant such instance was Project Cirrus in 1947. Project Cirrus was a collaboration between industry and the United States government—specifically the General Electric Corporation and the U.S. military. As an experiment, an airplane dropped 80 pounds of dry ice into the curved, elongated storm clouds (the “rainband”) circling around the eye of a hurricane headed away from land. The crew reported immediate changes in the cloud structure. The hurricane promptly changed direction and headed toward land. Whether either was a result of the dropping of the dry ice was unclear (and a source of great anger and lawsuits in the Savannah, Georgia area where the hurricane made landfall). The project was cancelled.
A more serious, sustained effort to alter hurricanes was initiated by the U.S. Weather Bureau and the Navy with Hurricane Esther in 1961. This became Project Stormfury. Project Stormfury was to go on to experiment on Hurricane Beulah in 1963, Hurricane Debbie in 1969, and Hurricane Ginger in 1971. It petered out after that, but was not formally brought to an end until 1983.
The hypothesis behind Project Stormfury was a variant of what had been attempted in 1947 with Project Cirrus. Convective clouds around the hurricane eye, in the rainband, were seeded with silver iodide. The intent was for this to enhance the thunderstorms in the rainband by freezing the supercooled water (water that is still in liquid form though it is below 32 F) in the clouds and liberate some of its latent heat of fusion. This would, in theory, cause the eyewall to break down, and a new one to form farther out, expanding the circumference of the eye. The strongest winds of a hurricane are found near the center—the more “tightly wound” the hurricane is the stronger it is—so moving the eyewall outward should result in a weaker hurricane.
Early results were encouraging but inconclusive. There was some weakening, but it wasn’t clear to what degree, if at all, it was attributable to the seeding, or just would have happened anyway. (There could be no “control” for the experiment, no identical hurricane left unseeded.)
More experiments and more observations, though, led to the conclusion that the seeding had little if any effect. It turns out there is not as much supercooled water in the clouds of the rainband as had previously been believed. Furthermore, the eyewall of a hurricane is now recognized to be a more complex structure that already forms, even if left unseeded, an additional outer layer of storms like the seeding was intended to create to compete with the inner eyewall. So to the extent that that weakens hurricanes, nature was already doing it for us.
Project Stormfury was a failure. But many climate scientists contend that in an indirect sense it was a success, in that the actions taken to test its hypothesis and conduct its experiments generated a great deal of valuable information about hurricanes and related phenomena that otherwise would have remained undiscovered.
Sources:
“Early Attempts to Control Hurricanes”
“Has There Ever Been an Attempt or Experiment to Reduce the Strength of a Hurricane?”
“Project Stormfury Attempted to Weaken Hurricanes in the 1960s and 70s”
