🌧 Cloud Seeding How Science Makes It Rain

Cloud Seeding How Science Makes It Rain

It just might work

It sounds like the stuff of cartoon supervillains, but weather modification techniques like cloud seeding could be a powerful tool as the planet warms and droughts worsen.

Seeding clouds aims to squeeze more precipitation out of them, boosting rainfall in dry areas and adding to the snowpack that feeds streams and rivers winding down from mountains. It’s a product of WWII-era scientific utopianism resurrected to head off climate-change-era dystopias, and it could be a last-ditch effort to halt global warming itself. Water managers from Australia to Israel to the American West are investing millions of dollars into the technique, with China—which has a considerable need for it—leading the way.

But like cartoon supervillains, we don’t know if our tech works. Despite its long history and the fairly basic principles behind it, proving the technology’s efficacy is a devilishly difficult science experiment. Let’s check the forecast.


5%–15%: Amount of extra snowfall a 2014 study determined we could induce through cloud seeding, under the best conditions

120 mm: Maximum annual rainfall in the United Arab Emirates

$558,000: Amount the UAE spent on cloud seeding in 2015

56: Countries that cloud-seed

10: US states that cloud-seed

$17–$21: Cost per acre-foot of renting water, according to Idaho water manager Shaun Parkinson

$3.50: Estimated cost per acre-foot of generating water through cloud seeding

$168 million: Cost of a recent Chinese cloud-seeding experiment

100: Cloud-seeding machines in Colorado

$1 million: Annual cost of Colorado’s cloud-seeding program

1 million: Number of cloud droplets needed to make a raindrop


How do you seed a cloud?

Cloud seeding is supposed to wring more precipitation out of a cloud using water vapor that’s already floating in the air, waiting to fall.

Some types of clouds are full of “supercool” water vapor—which means the droplets are colder than 0°C (32°F), but they haven’t frozen yet. Although your science teacher might have glossed over this, water doesn’t automatically freeze when it hits the freezing point. It takes some doing to get free-flowing liquid water molecules to arrange themselves into the orderly crystals that form ice. Once the water gets cold enough, it needs a seed to kick things off.

A seed can be almost anything—a fleck of ice, a dust particle, or even some species of bacteria. Cloud seeding generally uses silver iodide, which has a chemical structure that closely mimics an ice crystal. There are different methods for getting the seed into the clouds. You can shoot silver flares out of an airplane, or you can use ground based machines to float the particles into the air like incense.

Once the seed particles hit the cloud, the theory is that supercool water droplets will glom onto them, form ice, and then more droplets will attach onto that ice. Before long, they’ve formed snowflakes heavy enough to fall, and voila—extra precipitation hits the ground below.

☔️ The world’s supply of cheap and clean water will likely plummet as the climate warms and populations boom. Can we find ways to conserve, cut waste, and find new sources before it’s too late? 

Cloud Seeding How Science Makes It Rain

Cloud seeding apparatus on attached to an airplane wing.


Vincent “The Snow Man” Schaefer is widely credited as the father of cloud seeding. He also became the first scientist to create an artificial snow storm while working at the General Electric Research Laboratory in 1947. Watch him literally exhale a storm in what remains probably the coolest vape trick of all time.


How the Vonnegut brothers got obsessed with ice

To this day, no one has developed a more promising method of seeding clouds than Kurt Vonnegut’s big brother Bernard. In 1946, Bernard Vonnegut worked alongside Vincent Schaefer and Irving Langmuir at General Electric as they were doing their early experiments on cloud seeding. Schaefer discovered that he could seed clouds with dry ice. But Vonnegut realized he could do it better with silver iodide, which more closely mimics the chemical structure of water ice.

Kurt joined his big brother at General Electric a few years later, taking a job as a PR man. Heavily influenced by his brother’s research, Kurt wrote Cat’s Cradle in 1963. The novel’s plot hinges on the invention of “Ice-9”—a seed crystal that could freeze any water it came in contact with, and a weapon of mass destruction that could only be dreamed up by someone whose brother was one of the fathers of cloud seeding.

Fun Fact

Cloud Seeding How Science Makes It Rain

In 2009, Chinese state media announced that 12 highways around Beijing were closing because of heavy snowfall the government had induced through cloud seeding.

In 2009, Chinese state media announced that 12 highways around Beijing were closing because of heavy snowfall the government had induced through cloud seeding.


But does it work?

First we have to figure out, well, how we would figure that out. Consider the difficulty of setting up a randomized trial. The Wyoming Weather Modification Pilot Program, a well-designed, decade-long cloud seeding experiment, used two mountain ranges close enough to each other that they were often hit by the same storms, a good point of comparison. But that also meant they were cross-contaminated. Seeding was supposed to run for a day and a half when conditions were right, but they didn’t always stay right long enough. Weather is a byword for unpredictability, and you need predictability for results. As Christie Aschwanden details at FiveThirtyEight, “we may never know precisely how well cloud seeding works.”

That’s why governments haven’t shot the moon on cloud-seeding, but it’s also why they haven’t dumped it either. The United Arab Emirates has been running a cloud-seeding program since 2000, and recently gave out three $5 million prizes for rain enhancement science. Zimbabwe put $400,000 towards it this year. Delhi is likely to use it to combat air pollution. Iran has a cloud-seeding research center.

Cloud Seeding How Science Makes It Rain

Cloud seeding apparatus on attached to an airplane wing.


Sending climate change to seed

One possibility for the technology is more directly combating climate change through cirrus cloud thinning (CCT). It uses the same technology for a different purpose: In this case, making water droplets bigger would make cirrus clouds thinner, which would dissipate faster, which would result in less heat trapped in the atmosphere. One study found that this would lower global temperatures by 1.4°C (34.5°F), which is a lot.

So why not? First, it might do the opposite. Second, if did work, it might do stuff like “cause freaky weather all over the world” and “the globe’s wind patterns could change completely.”


Man vs. Hurricane

Vincent Schaefer—the aforementioned “Snow Man” who brewed snowstorms in his General Electric lab—was also the seed of a secretive US government program intended to kill hurricanes through cloud seeding. Thanks to the efforts of him and his research partner, Nobel laureate Irving Langmuir, the American military funded two decades of assassination attempts against major storms.

Schaefer and Langmuir had a promising theory. They believed that if they dumped silver iodide into the eye of a hurricane, they could cause the storm to form a new, bigger eyewall. That sounds scary, but it’s actually a good thing: A bigger eye means a smaller pressure gradient and less destructive winds.

On Oct. 13, 1947, Project Cirrus flew its first mission. An Air Force jet flew over a hurricane that had been heading harmlessly out into the Atlantic Ocean and dropped 180 pounds (82 kg) of crushed dry ice into the storm. The crew reported a “pronounced modification of the cloud deck seeded.” Soon after, the hurricane abruptly changed course and made landfall near Savannah, Georgia. The public blamed the destruction on cloud seeding, lawsuits followed, and Cirrus was cancelled. It took 12 years for the government to officially admit that it had seeded the storm.

The military quietly carried out a few experiments after the Cirrus disaster, but didn’t officially reboot the program until 1962. It was rechristened Project STORMFURY and experimented on several hurricanes until 1971. STORMFURY never produced any conclusive evidence that cloud seeding could weaken a storm, but it did fund extensive meteorological research that helps guide our hurricane predictions to this day—and the dream hasn’t fully died.


The New York Times explains how one species of bacteria beat humanity in the cloud seeding race by several million years.