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Silver-Lining Playbook
Scorned for years as the stuff of science fiction, cloud seeding could be a surprising new weapon in the fight against worsening droughts.

Any time he wants, Arlen Huggins can find out if he’s making it snow in Colorado. From his desk in a spacious, sunny office in Reno, Nevada, Huggins can pull up a screen on his computer and look at charts tracking relative humidity, temperature, wind direction, and wind speed at the Winter Park ski area, about an hour and a half west of Denver. The charts also show him the flow rate and flame temperature for a silver iodide generator perched near the resort’s 12,000-foot summit. He can control the generator from his desk. Its purpose is to build better clouds.

Weather modification is one of the least understood environmental practices going on today. Mention it at a cocktail party and people will say, “That’s not real, is it?” Others will launch into perfervid speculations about “chemtrails” and secret global “weather wars.” They may quote shock jock Alex Jones, who expressed surprising faith in government competence by suggesting the feds could have manufactured the recent Oklahoma tornadoes. But weather mod, as industry folks call it, is neither myth nor conspiracy. It’s a pretty standardized practice that’s been used since the 1950s. Huggins’s employer, the Desert Research Institute, part of the Nevada system of higher education, has been seeding clouds since the 1960s. DRI now has two programs in Nevada and one in California’s Sierra Nevada. Last winter they had logged more than a thousand hours of seeding by the time I visited in February.

The DRI campus is perched on a scrubby hill at the edge of Reno. The main building has a rounded concrete cornice and gleaming windows reflecting the Sierra Nevada. The place looks like HQ for a cabal of scientists intent on starting World War C, but its real aspirations are much more modest. Funded by the state, by irrigation and water districts, and by federal agencies, DRI’s scientists are working to increase the snowpack that feeds Nevada’s water supply by at least 5 percent and perhaps as much as 15 percent. Those numbers are hardly insignificant when conditions in the West have spawned talk of “mega-drought” and “regional disaster.”

Bernard Vonnegut

There have always been crazy schemes for modifying the weather: rain dances, hail cannons, intentionally set forest fires. Cloud seeding with aerosolized silver iodide was invented in 1946 by the GE scientist Bernard Vonnegut—the novelist Kurt’s older brother. A promising young chemist, Vonnegut was working with the Nobel laureate Irving Langmuir and his associate Vincent Schaefer when the pair discovered that seeding clouds with dry ice could encourage them to precipitate. Vonnegut figured out that silver iodide would do the same thing—and last longer. When GE announced the discoveries, newspapers and magazines ran stories declaring that the nation was finally going to do something about the weather. GE began working with the military on Project Cirrus, a series of weather-control experiments designed to make rain, divert hurricanes, disperse fog, and quench forest fires. At the same time, the Weather Bureau conducted experiments of its own and began publicly denouncing the Project Cirrus claims.

The debate between weather mod believers and skeptics has raged ever since, but the converts have been slowly gaining ground. In the 1960s the Bureau of Reclamation conducted rainmaking experiments over reservoirs under the name Project Skywater. In the 1960s and 1970s, a joint U.S. Navy–Weather Bureau exercise, Project Stormfury, attempted to modify hurricanes with seeding. And during the Vietnam War, the U.S. military flew cloud-seeding missions over Laos in an effort to make the Ho Chi Minh Trail impassable to North Vietnamese trucks.  It was called Operation Popeye. (Science-fictional code names are endemic to weather mod.) When news of Popeye broke, an international outcry led to a U.N. treaty banning large-scale weather modification in war.

Research spending on weather mod surged throughout the 1970s and then dwindled. Factors blamed for the field’s decline include early overpromising, the lack of rigorous research in the field, environmentalists’ reluctance to alter nature, and Reagan-era reductions in government funding. Another key element: the early 1980s were an exceptionally wet period in the United States. The weather modifiers have a saying for this: “Interest in cloud seeding is soluble in rainwater.”

The recent extreme drought has caused a resurgence of interest in anything that might increase water supplies. And now, improved instrumentation means results can be more accurately gauged. But there’s still a dearth of good research, which means a lack of conclusive evidence that cloud seeding works. Skeptics point to a National Academy of Sciences report in 2003 finding “ample evidence” that seeding clouds with a chemical agent like silver iodide caused them to produce more ice crystals, but no actual proof that this produced “credible, repeatable changes in precipitation.”

Nevertheless, cloud-seeding operations continue in many western states, funded mostly by water utilities, hydropower producers, agriculture groups, and ski resorts. There were at least 66 programs operating in 2001, spread out across 10 states. Today, in Wyoming, Idaho, Colorado, California, Utah, and Nevada, rainmakers are hired to augment the snowpack. In Texas and Kansas, cloud seeders are at work to induce rain. In North Dakota, clouds are seeded to make them precipitate before they can produce crop-damaging hail.  California, Nevada, and Arizona contribute funds to cloud-seeding projects over the Colorado River’s upper basin, in hopes of augmenting their water supply.

* * *

Jeff Tilley, DRI’s director of weather modification, is a compact man with intense brown eyes and a habit of speaking in long, complex, yet perfectly lucid sentences. Rather than saying he saw a beautiful sunset, he’ll describe “the interplay of the setting sun with a couple of distinct cloud layers and mountain topography.” A meteorology PhD, he was recently hired by DRI from the University of North Dakota.

Jeff TilleyTilley took me to see the institute’s silver iodide generator on the western shore of Lake Tahoe. As we drove up I-80 into the Sierra Nevada from Reno, we were accompanied for miles by an impressively long wooden flume—one of many pieces of nineteenth-century hydro-infrastructure that dot the Nevada landscape. It was a tangible reminder that settlement of the intermountain West has always depended on one thing: control of water. Capturing water, reserving water, redirecting water, owning rights to water. While in Reno I bought a postcard that showed two farmers whacking each other with shovels. “Discussing water rights,” it read. “A western pastime.”

“Cloud seeding is probably going to be an increasingly important tool for water resource managers in a changing global climate scenario,” Tilley said. “As drought areas increase and populations increase in areas subject to drought, or arid in the first place, cloud seeding provides a very cost-effective alternative for getting water resources.”

DRI’s cloud-seeding generator is near the top of Ward Peak, a mountain 8,643 feet high that hulks between Lake Tahoe and the Pacific Crest trail. To get there, we went to the Alpine Meadows ski resort and rode the lift to the top. A short hike in a brutal February wind and we were standing at the base of what looked like a restaurant exhaust fan. A green metal cube with a jerry-built black smokestack on top, it had a residential-size propane tank next to it, a photovoltaic panel mounted on its side, and what looked like a salvaged swimming pool ladder welded to the front.

Tom Swafford, the project’s field technician, got out a key and opened a small door on the contraption’s front.

“C’mon inside,” he said.

We ducked into a room the size of a pickup bed. Swafford pointed out the control panel, the radio link, the pressurized solution nozzle, the electronic flow meter. Tilley took out his cell phone and called Arlen Huggins back at DRI headquarters.

“We are at the generator,” he said. “We’re ready.”

There was silence as we huddled in anticipation. Then came a few clicks and a deep thunk as the generator flame lit. After a few moments, when it was hot enough, a whirring sounded as the silver iodide solution began flowing into the box, where it’s ignited and sprayed toward the sky.

We went outside, but the day was dry and clear, so the plume was not visible. Even when it was humid, Swafford said, you could barely see the aerosolized silver iodide streaming into the clouds.

A skier in a jacket emblazoned with a red cross and a badge that read Avalanche Forecaster shooshed up.

“Ever since you guys put this thing in, we get more avalanches right here than we get on the rest of the mountain,” he said. Everybody laughed. Weather mod folks love jokes like that. But Gary Murphy, the forecaster, wanted to be sure I got it.

“Not really,” he said, glancing at my tape recorder. “That’s not really true.”

* * *

DRI sometimes gets phone calls from irate ranchers in eastern Nevada who insist the Tahoe cloud seeding is “stealing” their rain. Jeff Tilley told me it’s a misconception that cloud seeding robs Peter to pay Paul.

“What cloud seeding actually does is enhance the ability of any given cloud system to precipitate,” he said. “It not only helps the water that’s originally within the cloud to be utilized better, but it also helps that cloud utilize the surrounding water vapor much better. You’re really getting more efficiencies from the water in the atmosphere and in the clouds. That water resource can actually be transported downstream and used later on by other cloud systems.”

NRDC: Fighting Drought

Robert Moore

Robert Moore

Senior policy analyst in NRDC’s Midwest office and head of the water and climate team

Advocates of cloud seeding have always confronted a lot of skepticism because of the dearth of hard data about its effectiveness.

As cloud-seeding experts themselves recognize, you can’t create rain or snow out of thin air. When you successfully seed a cloud, you’ve essentially stimulated the creation of lots of little ice crystals, which grow quickly and fall as either rain or snow, depending on the temperature closer to the ground. The technique basically tips the odds a bit in favor of precipitation in a particular place at a particular time, when favorable conditions already exist.

Scientists in a number of western states are now claiming evidence of more encouraging results from cloud seeding. If those claims are true, would that be enough to satisfy the skeptics?

To answer that question, you’d have to look at when and where the precipitation is falling and ask whether it might have fallen somewhere else if the cloud seeding hadn’t happened. Those are difficult questions to answer, but as cloud seeding is more widely deployed, they will certainly be asked by people living in areas downwind or downstream that are in the middle of a drought. It’s hard to say that the same cloud system wouldn’t have dropped snow or rain an hour later, or a day later, or 200 miles away if it hadn’t been seeded.

Even if the results of cloud seeding are modest, in a drought as severe as the one we’ve experienced for the past decade, shouldn’t we be using every weapon at our disposal?

Yes, there’s no doubt that as the climate warms and water supplies get tighter, we need to get innovative about how we manage them. If cloud seeding increases local precipitation, that is going to seem useful in particular circumstances. That’s why you see it being done in ski areas, for example, or around specific water-supply reservoirs. But cloud seeding won’t solve our bigger drought problems. As it gets hotter and drier, efficient use of water is the cheapest and most reliable way of making more of it available for future use. In the energy world, the cheapest kilowatt of electricity is the one you never have to generate. The same goes for water. The cheapest gallon of water is the one you never take from the tap. And there’s only a finite amount of water on the planet. We’re not making more of it.

That is why rainmakers say “rainmaking” is a misnomer. They can’t make rain. But they can increase the efficiency of the precipitation process.

Most of us think of clouds as reservoirs of water up in the sky. Cloud physicists think of clouds as factories. Those fluffy cotton wads or mackerel scales are visible markers of the process by which the atmosphere recruits water vapor from the air, from bodies of water, even from the pores of plants, and converts that vapor into droplets. Those droplets might fall to earth as rain or snow. But the vast majority don’t. They just hang there, going to waste. This is partly because most water droplets need something to cling to—a nucleus—to make them heavy enough to fall. Over the warm ocean, salt from evaporated water serves as a nucleus; that’s why places near the ocean often get plenty of rain. Over land, cloud droplets nucleate on dust, soot from forest fires, or microscopic particles shed by the earth. But not all particles are equally good at producing precipitation. Pollution particles, for instance, cause clouds, but are usually too tiny to precipitate. The drops don’t get heavy enough. Off the polluted Indian subcontinent, huge clouds form, but rarely produce rain.

A particle of silver iodide is an ideal nucleus, probably because its crystalline structure is similar to that of ice. Other substances work too—lead iodide and certain salts—but silver iodide is considered the most efficient. Not everyone believes this. Some people fear that silver iodide will pollute the groundwater when it falls to earth in precipitation. A widely quoted claim on the Internet is that the Environmental Protection Agency classifies silver iodide under the Clean Water Act as a hazardous material and a pollutant. But the EPA says this is untrue.

I contacted the agency and was told that silver iodide is not regulated under either the Clean Water Act or the Safe Drinking Water Act. The Centers for Disease Control and Prevention describes it as “a non-soluble compound not likely to produce toxic effects from either silver or iodine.” The Occupational Safety and Health Administration sets no limits for occupational exposure to silver iodide.

As for non-humans, DRI’s Huggins told me that in laboratory studies, silver ions added to aquariums proved capable of bonding to the gills of nymphs or trout fingerlings, inhibiting breathing. But this, he said, would never occur through seeding, since the amounts of silver iodide used are so tiny. The background concentration of silver in snow is about 2 to 4 parts per trillion. After seeding, you might find 20 to 30 parts per trillion.

“If you average it throughout the snowpack,” he said, “it’s barely above background.”

* * *

Even if silver iodide is proved to be completely benign, and if new studies prove that it really works, the idea of modifying the weather still makes some people cringe. Gary Walker, president of the Weather Modification Association, dismissed this response as naive.

“We’re messing with nature advertently—or inadvertently—every day,” he told me. “Every time you turn on your car, you’re changing nature. You heat your house, you’re changing nature. We think God gave us a brain so we could use it. But we do have our detractors.”

Lately, detractors are increasingly outnumbered by people who feel we should try almost anything to avert the looming water crisis. As a Denver Post editorial put it, “When it comes to water in the West, is any idea too crazy?”

I met Walker at the WMA’s annual meeting, held in April in San Antonio. On day one, the program had to be rearranged because some presenters were delayed by a huge storm system in the Great Plains. The rainmakers were obstructed by rain.

The conventioneers—mostly male, mostly pushing past middle age—came from utilities and universities, but also from private companies with such names as North American Weather Consultants and Weather Modification Incorporated. In the Marriott conference room, they took turns giving PowerPoint presentations with titles like “Winter ‘Cloud Seeding Windows’ and Potential Influences of Targeted Mountain Barriers.”  Most papers seemed to reach a similar conclusion: cloud seeding is tricky. You can’t seed just any clouds. They have to be the right temperature, at the right altitude, and near winds of the right speed and direction. You have to use the right seeding material and seed the bottom or the top, depending on the cloud. And knowing the characteristics of your cloud? That’s not easy either.

The weather mod world is eagerly awaiting the results of a randomized study being conducted in Wyoming. It is rigorous in its design, and the feeling is that it will bring new credibility to the field. Although the study won’t be released until summer 2014, a scientist on the project gave an update at the WMA meeting. He reported that he and his colleagues were expecting to announce, with 95 percent confidence, precipitation increases of 10 percent in seeded clouds.

“We’re messing with nature advertently (or inadvertently) every day ... Every time you turn on your car, you’re changing nature. You heat your house, you’re changing nature."

“We’re getting better,” said one private weather mod consultant whose clients include Pacific Gas & Electric. “I look at it like fishing. You go out there 10 times and how many times do you get a big fish? You have to have all your elements lined up.”

When he showed charts from his operations indicating precipitation increases of up to 26 percent, there was an audible murmur in the crowd. An attendee from PG&E sitting next to me nodded eagerly. PG&E generates electricity. An extra inch of snowpack in the Sierra Nevada might not be a bonanza for the water supply of Los Angeles. But running an extra inch of water through your turbines—that’s real money.

The last presenter at the meeting was Roelof Bruintjes, head of weather modification at the National Center for Atmospheric Research. He delivered a half-hour tsunami of data drawn from seeding efforts in water-insecure places as far-flung as Mexico, Australia, Indonesia, and the United Arab Emirates.

“Oftentimes if you do one experiment you get one kind of result, but if you do it again you get a different result,” he began. “This could be because of natural variability, or it could be because it’s a different kind of cloud.” He whipped through slides showing how clouds differ—not just worldwide, but even, say, in north Texas versus south Texas. Clouds in dry years are different from clouds in wet years. He put up charts showing that the seeding effect is greater on days with high “aerosol burden,” meaning when lots of fine particles, liquid or solid, are suspended in the air. When the air is clean, clouds are more efficient already and the seeding effect is smaller.

“Unless we know what nature is producing, it’s very difficult to know what seeding will produce,” he concluded. At the end of his presentation, there was thunderous applause. He had spent half an hour telling them their jobs were well-nigh impossible. They loved it.

A cloud-seeding generator station sits atop Ward Peak in the Sierra Nevada range. Photo: Justin Broglio/Desert Research Institute

Weather is perhaps the most discussed yet least understood phenomenon of daily life. These two things are related. We talk about the weather so much because we can’t do anything about it. That’s not about to change.

“This idea of controlling the weather is a misnomer,” Don Griffith told me. “We can do minor modifications on a local basis.”

Griffith was introduced at the WMA meeting as “the godfather” of weather mod. President and part-owner of North American Weather Consultants, one of the oldest private companies in the field, he is an imposing man with a shock of photo-white hair. A handful of younger attendees always buzzed around him. He wore a suit with a bolo tie to the meeting; he said the clasp depicted the Zuni god of thunder.

Like many in his field, Griffith was always fascinated by weather. Growing up in Denver, he was so excited that he used to run outside in his skivvies to measure the snowfall. An ROTC candidate in the Air Force, he became a weather officer during the Vietnam War. He remembers pointing out to his supervisor the frequent thunderstorms over North Vietnam. At the time he didn’t know the military was cloud seeding it.

Griffith only sees his business increasing as the population expands and water gets more scarce. But weather mod is not a panacea. “It’s one arrow,” he told me, “in a quiver of possibilities you can consider. But it’s typically one of the cheapest.” Building and operating a desalination plant—as Orange County, California, is currently doing—costs between $1,000 and $2,000 for every acre-foot of water it yields. Griffith told me that the typical cloud-seeding contract can yield that same acre-foot of water for five to fifteen dollars.

Many of Griffith’s clients come to him when they are already in a drought. He calls this “hydrologic illogic.” By that time, they may not have clouds to seed, or they may have clouds but not the right kind. He recommends seeding yearly—in wet years and dry—to build up supplies. It’s like putting money in your IRA: you do it when you have a job, not when you don’t.

In spite of his obvious enthusiasm, Griffith was careful not to overstate his claims. He told me that historically overselling had set the field back. No one should underestimate the difficulty of altering nature, whether through weather mod or flood control or damming rivers. But weather is especially tricky.

“The atmosphere is so variable and complex,” he said. “There’s still a lot we don’t know about it.”

This is why, though it may seem surprising, weather modifiers have little enthusiasm for geoengineering. No one I talked to at the WMA considered himself a geoengineer. After two days of papers on the complexities of weather mod, I understood why. When dozens of scientists are using radiometry, ground generators, and aircraft in an attempt to produce 10 percent more snow in Wyoming’s Wind River Mountains, when Pacific Gas & Electric has spent half a century toiling to get an inch more water into its turbines, claims that you can reverse global climate change with iron filaments, reflective aerosols, or oily stuff on the ocean look downright ignorant.

I asked Jeff Tilley of the Desert Research Institute about geoengineering. He told me that he feared more than just the risk of unintended consequences.

“Some of the B-movies on the SyFy Channel exaggerate to extremes,” he said, “but they point out the potential that [geoengineering] can be used as a weapon. And that scares the crap out of people. It scares the crap out of us, as the people who do weather modification, because we don’t want to do that application, and we don’t want to see anybody else do that type of application.”

Tilley grew up in Johnstown, Pennsylvania. He was a child during the town’s third historic flood, in 1977. It was caused by a series of thunderstorms that meteorologists call a train because they roar down the same track. His parents woke him up at 2:30 in the morning to help them bail water out of the basement. The family’s neighbors were trapped on the second floor of their newspaper offices downtown for a couple of days. They ate food out of vending machines and watched their station wagon float by. They were lucky. Six dams failed in that flood, and 85 people died. Tilley had already been thinking about becoming a meteorologist, but the Johnstown flood clinched it.

“I got into weather and applications of weather modification,” he said, “because I want to do something to help.”

Photo of Bernard Vonnegut from Bernard Vonnegut Papers, M.E. Grenander Department of Special Collections and Archives, University at Albany Libraries

Photo of Jeff Tilley by Toby Burditt

Photo of cloud-seed generator by Justin Broglio/Desert Research Institute

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Ginger Strand is the author of a novel, Flight, and two books of nonfiction: Inventing Niagara: Beauty, Power, and Lies and Killer on the Road: Violence and the American Interstate. She writes for a variety of magazines, including Harper’s, Wired, and Orion, where she is a contributing editor. MORE STORIES ➔
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The management of continental water resources was addressed by Parsons engineering firm in their design North America Water and Power Alliance (NAWAPA) and espoused strongly by John F. Kennedy before he died. Parsons still displays NAWAPA on their webpage and currently it is being pushed by many young people hoping for the 6 million jobs the project proposes to save our aquifers and kick start our agricultural and industrial productivity. With this many paychecks our nation would have a tax base to continue providing improved public services in education, law enforcement, transportation and health care. Reliable source of water to the Canadian mid-west as well as the Mexican arid regions would greatly enhance the prosperity of those neighbors and be the best solution to our so-called immigrant problem. Seeding is a short term solution that may help however the challenge of water supply for our species must be the # 1 priority for not only our continent but others. Africa's lake Chad is drying up and desertification probably contributes to east coast North American hurricane devastation. Those countries need the inspiration of seeing the U.S. take charge of water management. Note the 50 year project that Holland found necessary to control water around its nation. Also note that huge projects in the U.S. were taken when economic depression was prevailing but constitutionally provisions have been make for building public welfare projects. We have seen historically the viaducts in Rome and the pyramids so today's lack of efforts to provide for our needs while engaging in munitions production and use is striking. We seem to be our own worst enemy. I write hoping you will be able to place the NAWAPA more prominently in the media as a solution to our many challenges. Thank you for your work providing leadership in the media.
Shifting rain patterns seems hardly a solution and quite expensive, but highly profitable for some. ''''''''It seems the only way to ensure the safe water supply for the world is to supply more civil and pragmatic guidance in the area of population control. The ability and zeal to produce more babies without consequences is bringing the world to a precipice of all educable circumstances that may be irreversible. It reflects the further ignorance of political officials to govern sanely when and where needed most.