What we cannot do

The versions of weather modification that the conspiracy theorists envision most often—significantly altering monsoons or hurricanes or making the skies clear and sunny for weeks at a time—have so far proved impossible to carry out. But that’s not necessarily for lack of trying.

The US government attempted to alter a hurricane in 1947 as part of a program dubbed Project Cirrus. In collaboration with GE, government scientists seeded clouds with pellets of dry ice, the idea being that the falling pellets could induce supercooled liquid in the clouds to crystallize into ice. After they did this, the storm took a sharp left turn and struck the area around Savannah, Georgia. This was a significant moment for budding conspiracy theories, since a GE scientist who had been working with the government said he was “99% sure” the cyclone swerved because of their work. Other experts disagreed and showed that such storm trajectories are, in reality, perfectly possible without intervention. Perhaps unsurprisingly, public outrage and threats of lawsuits followed.

It took some time for the hubbub to die down, after which several US government agencies continued—unsuccessfully—trying to alter and weaken hurricanes with a long-running cloud seeding program called Project Stormfury. Around the same time, the US military joined the fray with Operation Popeye, essentially trying to harness weather as a weapon in the Vietnam War—engaging in cloud seeding efforts over Vietnam, Cambodia, and Laos in the late 1960s and early 1970s, with an eye toward increasing monsoon rains and bogging down the enemy. Though it was never really clear whether these efforts worked, the Nixon administration tried to deny them, going so far as to lie to the public and even to congressional committees.

More recently and less menacingly, there have been experiments with Dyn-O-Gel—a Florida company’s super-absorbent powder, intended to be dropped into storm clouds to sop up their moisture. In the early 2000s, the company carried out experiments with the stuff in thunderstorms, and it had grand plans to use it to weaken tropical cyclones. But according to one former NOAA scientist, you would need to drop almost 38,000 tons of it, requiring nearly 380 individual plane trips, in and around even a relatively small cyclone’s eyewall to really affect the storm’s strength. And then you would have to do that again an hour and a half later, and so on. Reality tends to get in the way of the biggest weather modification ideas.