Results Cloudy : Seeders Still Hope to Tap Water in Sky

The little twin-engine airplane flew unsteadily at 17,000 feet, flung by heavy turbulence through a mass of gray. Jagged mountain peaks waited a few thousand feet below, invisible from within the clouds. Sleet slapped ominously against the window. The pilot was pleased.

“Pretty good conditions,” Chuck Sheridan said.

Sheridan is a cloud-seeder, and the miserable weather told him that this particular cloud was ripe for his manipulations. He threw a switch and a thumb-sized pellet of silver iodide mounted on the wing ignited and fell away.

Theoretically, the descending pyrotechnic would induce a chemical process to wring from the cloud more snow than it would deliver naturally. Eventually, the snow would melt and, carried by creek, river and canal, make its way to reservoirs of the Los Angeles Department of Water and Power.

Seductive Notion

What a grand, seductive notion. Fly into the clouds, flip a switch and whip up a little water for greater Los Angeles. Presto. Unfortunately, there are complications--like nagging uncertainty about whether the process actually works as advertised. Cloud-seeding remains largely an exercise in the empirical--an act of faith in laboratory experiments, vague statistics and a theorem of capitalism that any product that can continue to sell must have merit.

Frustrated, many scientists have abandoned the quest for unassailable statistical evidence that the 40-year-old technology can enhance rainfall on command. Instead, they have retreated to the more fundamental question of what transpires naturally within clouds.

“I think the attitude in weather modification has been, ‘Let’s get on with it and do it and we’ll worry about the longhair stuff later on,’ ” said physicist Bernard Vonnegut, an early pioneer of cloud-seeding research. “As a result, I think that we still don’t have a satisfactory background on how clouds work. And in the absence of that, it is pretty much trial and error.”

Handful of Entrepreneurs

Nonetheless, a handful of commercial cloud-seeders continues to peddle the trade around the world. They have learned to sell softly, avoiding the outrageous claims that in the past tainted their professional image. No longer do they claim to engage in rainmaking. Instead, they prefer a more prosaic job description--weather modification.

The weather modification experts cast themselves as a water management alternative, less expensive than, say, constructing a new dam or canal system.

They claim to be able to enhance precipitation from a cloud by 5% to 25%. But they also take pains to point out that only clouds ready to produce rain on their own can be seeded. Thus, when the unrelenting blue skies of drought settle over a region, cloud-seeders can do little more than join the parched in prayer for rain.

In the United States, most cloud-seeding activity is conducted in the West. Out here, water is a commodity, bought and sold and shipped by the acre-foot. A technology that promises a chance of increasing water supplies can be seen as an investment, and the risk of its not working must be measured against the value of its potential yield.

The economic rationale for the Los Angeles DWP’s decision to seed this year for the first time in a decade is instructive. Confronted with an unusually light snowpack, the agency awarded a contract a Fresno firm, Atmospherics Inc., to seed the southeastern slopes of the Sierra for three months. The project is to end April 23. It cost $50,000.

If the minimum projections of the seeders are only half met--that is, if precipitation is increased by 2.5%--this would mean that the project generated 10,000 acre-feet of water. In a shortage, the DWP would buy water from another agency for $230 an acre-foot. So, with a $50,000 investment in cloud-seeding, the department conceivably could create $2 million to $3 million worth of water.

The proverbial downside in the decision is that no one will never know if the cloud-seeders produced one drop of additional water, let alone $2 million worth. “Statistically, you can’t pick out that small of increase for a one-year project,” said DWP official Doug Gillingham. “Nobody can go back and say what would have happened this year if we hadn’t seeded clouds.”

Began in Refrigerator

Cloud-seeding was born quite by accident 40 years ago in a refrigerator in Schenectady, N.Y. Vincent Schaefer, a scientist for the General Electric Co. Research Laboratory, was conducting basic experiments to determine why icy wings interfere with airplane radio signals.

One hot July day he found that the converted ice box serving as his experimental environment had grown too warm. So the scientist stuck a block of dry ice inside. As he did, a cloud formed by his breath came alive with tiny ice crystals--an essential step in the natural development of precipitation. Schaefer had created a miniature snowstorm.

Within months he was airborne, seeding clouds to produce what Schaefer later described as “draperies of snow.” Schaefer’s research partners were the late Irving Langmuir, a Nobel laureate, and Vonnegut, brother of author Kurt Vonnegut. It was Vonnegut who discovered that silver iodide could be used instead of dry ice.

Soon they began to seed in distinct patterns, seeking to lay down corresponding traces of snow on the ground below. “The most spectacular effect was a race track, 10 miles long” Schaefer said in an interview. “If you believe that was an accident,” he recalled Langmuir telling one persistent cynic, “the next time we go up there we’ll put down the GE logo.”

Project begat project.

Promise in Approach

Not only was there potential for creating precipitation in the West, but weather modification held--and, some say, still holds--promise for clearing persistently overcast skies in the East, for defusing hurricanes in the South, for blunting the impact of hailstorms across the Plains. Airstrips could be cleared of fog, ski runs packed with extra snow. Even the Department of Defense was interested, and years later the scientists were surprised to learn that during the Vietnam War the U.S. military had attempted to muddy enemy supply routes with a covert cloud-seeding operation.

In the winters, Schaefer conducted research at Yellowstone National Park, making artificial snowstorms out of steam from Old Faithful and other geysers. A participant in these winter projects was Tom Henderson, president of the firm seeding for the DWP.

Henderson got his start in cloud-seeding during the late 1940s in Barstow, where he worked for the old California Electric Power Co. The power company saw seeding as a way to create more water to run through its hydroelectric generators.

“They gave me the job of determining if there was anything to this,” he said.

Through the 1950s Henderson flew 300 cloud-seeding missions. He sat in the nose of a converted P-38 fighter plane and sprinkled dry ice into the clouds through a hole in the fuselage. His primary tool was a one-pound coffee can.

“It took me nearly five years before I was really a strong believer,” he said. “What you saw was some very interesting things happening suspiciously close to the time you seeded. What you saw was that when you dropped dry ice into clouds they changed . . . and rain and snow fell out the bottom.”

This is now called the “black box” era of weather modification. Seeders did not know what went on inside clouds, only that they seemed to be able to make rain. In this period, cloud-seeders attending scientific meetings were confined to seats in the back row, along with all the other witch doctors.

By the end of the decade entrepreneurial sorts had sniffed profit in the newfangled technology, and they were everywhere. Many were short on scientific know-how but long on salesmanship, boasting of guaranteed 400% increases in rainfall. The wild claims generated business--and demands for scrutiny.

Said Henderson: “Statisticians and atmospheric scientists were getting hammered by people to come forward . . . and see if these claims were true. There were a whole lot of experimental programs and analytical work done. What they found was that these claims were out of line.”

With the introduction of statisticians, cloud-seeding reached a pivotal point. What had begun as scientific exploration of clouds evolved into a quest to prove with rainfall and stream flow statistics that seeding worked and to measure its effectiveness. It is a change that scientists regret.

Scientists Trapped

“I think,” Vonnegut said, “that some excellent scientists got tied up in seeing whether they could make more rain or not. . . . This was not a building block of science. There is no guarantee if you do it that it can work the next time.”

The principal problem has been the scientists’ inability to control their laboratory--the sky. Clouds change constantly, making measurement of any artificial alterations extremely difficult. And all clouds are different. Lessons learned from an experiment over the Sierra in the winter cannot be applied to summer clouds in Florida. Seeding techniques that produce precipitation in some clouds have decreased rainfall in others. No one knows why.

After three decades of attempts, a 12-year project in Israel stands as the only successful effort to confirm that the technology works. And skeptics contend that it proved only that cloud-seeding worked at one specific location during one specific project. That the results indicate seeding would work elsewhere--or even again in the same location--is a leap they refuse to make.

Randomized Seeding

A federal project in Florida in the early 1980s was designed to confirm earlier indications that cloud-seeding there had produced solid results. It was an ambitious effort, employing randomized seeding of clouds and rigid statistical controls. It fell apart on a day when no seeding occurred, yet rainfall was six times more than normal. This threw all the statistics out of whack, crippling beyond repair the carefully designed experiment.

Failure of phase two of the Florida Area Cumulus Experiment exasperated scientists.

“We decided that statistics were not the way to go, that we had to go back to basics,” said Hal Corzine, manager of a National Oceanic and Atmospheric Administration program to monitor cloud-seeding activity. The agency had sponsored the $3-million Florida experiment, and shortly after its failure the agency withdrew from active pursuit of cloud-seeding.

“We decided that, of all the functions we had, that this was one that we had to put on the back burner,” Corzine said.

Research budgets have been sliced dramatically, down from a level of nearly $20 million a year during the 1970s to about $6 million annually.

‘Research at Low Ebb’

“The level of effort, of research, is at a low ebb, much lower than it was 20 years ago,” said Peter Hobbs, an atmospheric scientist at the University of Washington. “There is a general disillusionment in the struggle, and many scientists have moved to more fruitful areas of research.”

Hobbs has moved away from cloud-seeding research; one of his last investigations indicated that positive results attributed to seeding actually might have been created by the mere passage of airplane wings through clouds. He, too, has “gone back to the fundamentals.”

Commercial weather modification activity also has declined, although not as drastically. The number of private projects dropped from 46 in 1981 to 27 last year. In addition to cloud-seeding in the West, the commercial activity involves hail suppression and efforts to remove fog from airstrips.

Elsewhere in the world, several nations have vigorous cloud-seeding programs. The Soviet Union is a big believer in the technology, and its weather modification experts have taken credit in the past for clear skies over the Kremlin on May Day.

The U.S. scientists still involved in cloud-seeding are looking for ways to use radar to chart the inner workings of clouds, and they are bearing down harder on the intricate microphysics of the natural precipitation process.

‘Getting Closer’

“We are getting closer and closer,” said Henderson of Atmospherics Inc., “to a fairly strong ability to go up and measure something and from that know what is likely to happen--and then put our fingerprint on that chain of events and see how that chain of events changes. We are not there yet. And there is a lot to learn.”

Henderson left the power company in the late 1950s and started a commercial seeding business. He has done well. Atmospherics Inc., has landed contracts around the world and maintains a fleet of more than a dozen airplanes.

That commercial cloud-seeders like Henderson remain somewhat active despite the inability of science to prove the effectiveness of the technology is a dichotomy that some researchers believe has hindered progress.

“The business people in cloud-seeding say, ‘We know enough to do this,’ ” said Stanley Changnon, lead scientist for a seeding project conducted out of the University of Illinois. “And the research and development people are saying, ‘We don’t know how it works.’ I think these two things running in parallel have had the net effect of confusing the public.”

Changnon said he is often asked by Midwestern farmers whether to invest in cloud-seeding, and it is a ticklish equation. In the end, he said, “My response is that I wouldn’t invest.”

Ramifications Not Explored

Still left largely unexplored, he said, are potential social, ecological and legal ramifications of cloud-seeding. Changnon said cloud-seeding can involve “changes over hundreds of thousands of square miles. Whether or not you seed should be a community decision, not an individual decision.”

Rain that might help save an apple orchard could destroy a cherry crop in the next field. And snow that might slake the thirst of ranchers could mean extra snow removal expenses for residents of mountain towns. Part of the history of cloud-seeding is found in courtroom file stacks, as seeders occasionally have been accused in civil suits--without success--for triggering floods, avalanches and such.

Farmers and water managers saddled with shortages are less likely to burden themselves with sociological conundrums or, more importantly, with the scientist’s demands for perfect proof. These days, it seems all of agriculture is a long shot, and the hiring of a cloud-seeder can be viewed as just one more roll of the dice.

“The acceptable risk level should be determined by the user, and not the scientists,” said Bernard Silverman, who heads Project Skywater, a long-running effort by the U.S. Bureau of Reclamation to investigate weather modification.

Half Full, Half Empty?

“It’s like the old optimist-pessimist question,” said Silverman, a scientist. “Is the glass half full or half empty? The scientist is always going to be concerned with the half-empty part, while the farmer is more interested in the half-full part. That’s why there is a thriving commercial field: There are people out there willing to take the risk.”

Bouncing along at 17,000 feet in the clouds with Chuck Sheridan, it was difficult to keep the big picture sorted out. An oxygen mask and a tightly clutched cardboard box served as the only precautions against motion sickness, and there were many times when these seemed paltry allies.

The disorienting turbulence did not faze Sheridan. “Everybody thinks I’m crazy,” said the 47-year-old pilot. “I’m looking for bad weather. What most commercial pilots try to stay out of, I try to get into. But it’s not particularly dangerous. . . . “

For three hours the airplane droned up and down a 116-mile dogleg course from Lone Pine to Mono Lake. Along the way, 40 silver iodide cylinders were fired from the wings. They all disappeared into clouds. Who knows to what end.

Sheridan said he is positive that he had coaxed additional snow from the clouds. It wasn’t possible to see this, of course. In fact, it wasn’t possible to see much of anything in the clouds. Still, Sheridan had read the statistics, he had listened to explanations of the theory. And he is convinced that it works. He is convinced that for three hours he had made water for the thirsty of Los Angeles. Just like that.