Make It Rain

Cloud seeding sounds like science fiction, but it may become a useful tool to combat drought and lessen the risk of wildfires.

kerjon lee of the los angeles county department of public works examines cloud seeding trees, an automatic high output ground seeding system, at the kinneloa facility in pasadena
ZUMA Press

Kerjon Lee of the Los Angeles County Department of Public Works examines cloud-seeding trees—an automatic high-output ground seeding system—at the Kinneloa facility in Pasadena.

In Kurt Vonnegut’s 1963 novel, Cat’s Cradle, a scientist invents ice-nine, which is capable of freezing all the water on Earth. Of course it gets released, and apocalypse ensues. The ocean turns into a blue-white pearl under a darkening sun. Tornadoes fill the sky like worms. “The earth was locked up tight,” Vonnegut writes. “It was winter, now and forever.”

It’s a stark warning against monkeying with nature and, it turns out, Vonnegut was inspired by real life. In the 1940s, he worked as a publicist for General Electric alongside his brother, Bernie, a scientist. As part of a research team headed by Nobel Prize winner Irving Langmuir, Bernie Vonnegut helped invent cloud seeding, a process of using chemicals to stimulate rain. An aerosol—usually silver iodide—is released into a would-be storm cloud. Water droplets cluster around the tiny crystalline particles, growing heavier and eventually falling as rain or snow.

While Kurt Vonnegut worried about the implications of this untested technology, others rushed to adopt it, including some organizations in California. Pacific Gas and Electric has used cloud seeding since the 1950s to increase the snowpack in the Sierra Nevada. Today, districts from Los Angeles to Santa Barbara to Sacramento cloud seed to increase rainfall.

I was fascinated to learn about cloud seeding. Making it rain seems at once the oldest of human fantasies and utterly futuristic, yet apparently it has been going on for decades. I probably wasn’t alone in my surprise. Until recently, cloud seeding was mostly out of public consciousness, either forgotten or sidelined into a category of science that seems slightly musty and suspicious. But climate change, with its accompanying droughts and wildfires, has made people look at this technology anew.

Today, at least eight states, as well as private entities like ski resorts, use cloud seeding. Last summer, the United Arab Emirates flew planes loaded with silver iodide through some clouds. Soon after, the country’s national weather service posted videos of rain pouring down on a desert highway, pounding palm trees that usually endure 120-degree heat. Around this time, China shot rockets full of silver iodide into the air, bringing down so much rain in Beijing that it cleared away pollution in time for a political event.

This article appears in the Spring 2022 issue of Alta Journal.
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It all sounds wondrous, like something out of, well, a Vonnegut novel. But the reality of cloud seeding is much less exciting. For one thing, it requires a special set of conditions, including a cloud full of supercooled water. When it does work, the results are often modest. Most studies suggest that cloud seeding increases rainfall by around 10 to 15 percent.

“It’s not the solution to drought, but it’s a tool to take advantage of,” says Frank McDonough, the director of the Nevada-based Desert Research Institute’s Cloud Seeding Program, which operates in the Sierra and other areas. “It puts additional snow on the ground, which is useful, and it might also help make snow last later into the season. Snow is melting earlier now in higher elevations, and there have been significant wildfires in areas that have historically stayed too wet most years to have fires. So any extra snow is a good thing.”

getty images
irving langmuir, left, and bernie vonnegut, center, watch vincent schaefer try to turn his breath into ice crystals at general electric’s research laboratory,  the three helped invent cloud seeding in the late 1940s
Irving Langmuir (left) and Bernie Vonnegut (center) watch Vincent Schaefer try to turn his breath into ice crystals at General Electric’s Research Laboratory. The three helped invent cloud seeding in the late 1940s.
Schenectady Museum Association

Skepticism about weather modification is well justified. For example, consider the hail cannon, long considered bunk science. Invented in the 1890s to protect Austrian vineyards from frozen rain, the cannon looks like an enormous megaphone pointed at the sky. When a storm approaches, the cannon blasts out shock waves, getting louder by the second, until people have to yell to be heard.

The fact that hail cannons don’t work didn’t stop Mel Potter, a cranberry farmer in Wisconsin, from using one to safeguard his crops. In 2014, he explained why to a TV news reporter. “I’m absolutely positive it works,” he said. “Because for almost 20 years, we haven’t had any hail here. We used to pretty near every year have a little bit.” But the National Weather Service confirmed that there had been no hail damage in the area over the same period—whether or not one used a cannon.

This anecdote shows one problem with weather modification—it’s easy to read into results. Since each storm system is different, it’s hard to measure whether human intervention has any effect. It’s not as if you can run the same cloud through multiple experiments to get objective data. This means that often, cloud seeding ends up in a chicken-and-egg scenario: Did nature or people cause a given result?

Proving that cloud seeding works was a problem the GE scientists ran into in the 1940s. The team consisted of Langmuir, Bernie Vonnegut, and Vincent Schaefer, nicknamed the Snow Man because he was the first person to stimulate snowfall. Langmuir, who won the Nobel Prize in Chemistry in 1932, was the inspiration for the inventor of ice-nine in Cat’s Cradle. He was so absentminded that he once tipped his wife after a meal, mistaking her for a waiter—a detail Kurt Vonnegut included in the novel.

The team was researching supercooled water (which remains liquid below water’s usual freezing temperature) using a GE chest freezer. After lining the freezer with black velvet, Schaefer breathed into it so that a small cloud hovered inside the box. He tried different substances to get it to crystallize, but with no luck. Then, on a hot July day, the freezer was struggling to stay cold, so Schaefer added a block of dry ice. When he put it through the cloud, the drastic drop in temperature formed ice crystals that glittered and drifted down onto the black velvet. Schaefer had made a miniature snowstorm.

On November 13, 1946, the team scaled up the experiment. According to Ginger Strand’s 2015 book, The Brothers Vonnegut: Science and Fiction in the House of Magic, Schaefer and a pilot flew a prop plane from the Schenectady County Airport in New York to a cloud floating 60 miles away over Mount Greylock in Massachusetts. Once they were inside the cloud, Schaefer released three pounds of dry ice before his dispenser malfunctioned. Since he still had three pounds to go, he picked up the box of dry ice, opened the window, and dumped its contents. The plane roared out of the cloud, looped around, and went back in. This time, Schaefer was “surrounded by glinting crystals of snow.”

Langmuir, in the airport lookout tower, saw the whole thing. Strand writes:

Shortly after the plane disappeared into it, the cloud almost seemed to explode. Then it began to split horizontally, dividing into two parallel clouds. Falling from the space between them were long streamers of snow.

After this early triumph, the experiments continued. Bernie Vonnegut discovered that silver iodide worked best as a seeding agent, because its chemical structure is similar to that of ice. Then the military teamed up with Langmuir in Project Cirrus. Among other things, they wanted to see what would happen if they seeded a hurricane. In October 1947, they found a good one to try. Hurricane King had pushed through Miami and seemed to be calming down as it drifted out to the Atlantic. Three planes flew over the hurricane and dumped 180 pounds of dry-ice pellets into the boiling storm.

Instead of weakening, the hurricane went wacky. To everyone’s amazement, it made a 135-degree turn back toward the United States. It hammered Savannah, Georgia, causing $3 million in damage, killing one person, and enraging everyone else. Still, cloud seeding looked like the discovery of the century. There was a rush to use the technology, with private operators popping up all over the country. The topic was debated in Congress, and the military discussed using cloud seeding as a weapon. Senators asked, Who owns the clouds?

The hurricane story is the kind of fantastic scenario that cloud seeding tends to evoke. How to explain the storm’s strange behavior if it wasn’t caused by dry ice? It may simply have been a coincidence. Hurricanes change size and strength all the time. In 1906, another hurricane had done the exact same dogleg turn into Savannah as King, reports the Atlantic. History is full of stories of people attempting to change the weather and seeming to do so.

Katja Friedrich, an associate professor of atmospheric and oceanic sciences at the University of Colorado Boulder, thinks the Hurricane King story is a myth. “I would be highly impressed if that was really the case and they did that to the hurricane,” says Friedrich. “I think it’s overestimating the ability you really have of modifying the weather.”

Even though people have used cloud seeding to stimulate snowfall for decades, it was only recently unambiguously proved that the technology can make clouds snow. In 2017, SNOWIE (Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment), a National Science Foundation–sponsored project that Friedrich worked on, was the first to document the full cycle of cloud seeding. On three separate occasions in the mountains surrounding Idaho’s Payette River basin, researchers observed the cloud-seeding process from the insertion of silver iodide to snow hitting the ground. The events yielded enough water to fill 282 Olympic-size swimming pools. While that seems like a lot, it was spread over 900 square miles, which means only a thin layer of snow was produced.

Friedrich cautions that the cost and effort of seeding for a relatively small amount of snow might not be worth the trouble—especially when it involves flying into the clouds. Silver iodide is cheap, but airplanes are expensive to run and use fossil fuel, which has a negative environmental impact.

“It’s about efficiency,” says Friedrich. “We come back to the problem of, What is the cost of water and how desperate are we? Is it worth doing all this for just a little bit of water?”

In January, I drove to Santa Barbara County to see the cloud-seeding trees, called AHOGS (or automatic high-output ground seeding system). I wanted to get as close to the actual process of cloud seeding as possible. Or maybe I just wanted to see something that causes rain. In 2021, it was impossible to ignore the drought ravaging California. In April, heat waves began rolling over my house with such regularity that I no longer wanted to go outside. My town, Petaluma, restricted irrigation more and more, until we could water our yards only twice a week, at night. In June, I visited Shasta Lake, a reservoir near Redding, where the water level was so low that the houseboats bobbed beside the rusty banks like toys in the bottom of a draining bathtub. By the end of the year, a future where water was no longer freely available but expensive, controlled, and traded like a commodity felt perilously close.

Santa Barbara County has been cloud seeding since 1981, making its program one of the oldest in the state. The county contracts with a private company, North American Weather Consultants, to handle the seeding. Its AHOGS are located in strategic spots to target specific water basins. Studies show they will increase the precipitation from a weather event by a fair amount—9 percent in Twitchell Reservoir and 20 percent in Cachuma Lake.

The county hasn’t used airplanes for cloud seeding since 2017, in part because a ground generator like an AHOGS is more cost-effective. “The key is that the overall cost-benefit is really high,” says Garrett Cammans, the president of North American Weather Consultants. “So the benefit to a typical area generally outweighs the cost of other sources of water by 10 times. We’re producing water at $50 an acre-foot.”

The AHOGS site I was going to visit was located by a radio station on top of a rocky mountain peak. Looking up at the Santa Ynez Mountains, I could see a series of poles and antennae sticking into the hilltop, like needles in a pincushion. I drove up the curvy mountain road, passing joggers and bicyclists. Below, beyond the woolly hills, the sun shone onto the sea in a yellow streak, resembling a headlight reflecting on the water.

At the radio station, the AHOGS stood out for its distinctive appearance—a tall skeleton of an artificial Christmas tree with stubby metal canisters for branches. Each canister contained a flare with enough silver iodide to provide billions of potential sites for water droplets to cluster. When a storm moves in, between 3 and 20 flares are remotely ignited, depending on circumstances like wind speed and the amount of recent rainfall, if any. The firing canisters sound and smell like sparklers. For up to 45 minutes, beige smoke hisses skyward, lifted by the wind until it reaches the clouds.

how cloud seeding works graphic
MATT TWOMBLY

One of the biggest questions about cloud seeding is whether it’s safe. Studies have found that the concentration of seeding agents in the environment is minimal. Silver is almost completely biologically inert. When it falls to the ground, it sits in the soil as a tiny piece of metal. The silver and iodine concentrations in rainwater from seeded storms are below the levels that occur in nature.

But while these trace amounts aren’t considered a risk, that could change if cloud seeding is widely adopted. Silver iodide has shown some toxicity in aquatic life, including phytoplankton, and soil bacteria. There are no federal laws governing cloud seeding, so it’s left up to local or state authorities to decide whether to allow it. This means that rules about cloud seeding can range from outright bans to a free-for-all where every rich person who wants a snowy Christmas can give it a try.

Increasingly, people are investing money in solving the problems caused by climate change, even as the overall crisis continues to loom. Cloud seeding is part of the field of geoengineering, which is the development of technologies designed to mitigate the effects of the heating climate. For example, hydropanels, which might be mistaken for big-screen TVs, supposedly pull moisture from thin air and turn it into drinking water. Direct air capture, an array of fans in what looks like a giant muffin tin, vacuums carbon dioxide from the air. And controversial solar radiation management would reflect heat by putting aerosols into the sky, essentially cooling the planet by blocking the sun.

This last reminds me of 1816, the Year Without a Summer. The eruption of Mount Tambora in what is now Indonesia released so much ash that it spread all over the world and caused a volcanic winter. Crops failed, leading to widespread famine. That summer, 18-year-old Mary Shelley was trapped in a house beside a Swiss lake with several friends, including Lord Byron and her husband, Percy Bysshe Shelley. As the rain poured down, she wrote the first science fiction novel, Frankenstein, about what happens when man monkeys with nature.

In Cat’s Cradle, Vonnegut fictionalized his concern that cloud seeding could be turned into a weapon capable of ending the world. (He wasn’t too far off—the U.S. did use cloud seeding as a weapon during the Vietnam War. Through Operation Popeye, the military seeded storms around the Ho Chi Minh Trail in an attempt to intensify monsoon season.) The truth is, even after all this time, there’s a lot we don’t know about cloud seeding. Somehow it’s a technology that’s still in its infancy. In fact, NASA has launched a $30 million mission called ACTIVATE to study the science of aerosol-cloud interactions. Other organizations—private companies and government groups across the globe—are improving cloud seeding with new delivery methods, better research, and advancements in computer modeling and data collection. Over time, cloud seeding may provide new ways to help drought-stricken areas, fight fires, and ensure water supply. It could become a useful tool in any difficult years ahead.

Or maybe not.

In the end, it all depends on the weather.

“You see how complicated it is, and it can go either way,” says Friedrich. “But to assume that we are capable of manipulating the weather the way we want to, I think, is really wishful thinking.”•

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