- Photo courtesy of Larry Hjermstad, Western Weather Consultants
- Vail-area landowners earn between $1,200 and $2,500 per season to host and operate cloud-seeding generators on their properties.
Heading through Blue Sky Basin at Vail Mountain on a recent powder day, the snow at the country's most popular ski resort seems fluffier and fresher than that on other mountains.
For the past three decades, the largest single-mountain ski area in North America has been polishing its claim that "There's no comparison" when it comes to skiing and riding Vail. And the resort managers aren't above using a little atmospheric alchemy to earn that edge.
On days when the storm clouds are heavy and high, Vail Mountain ensures its runs stay stacked with deep snow by seeding the clouds with silver iodide to, supposedly, squeeze more water from the skies. According to some atmospheric scientists, cloud seeding can increase snowfall by 10 to 15 percent in a season, and Vail credits it among the reasons for its world-class reputation.
Vail seeds clouds to "make sure they have the premier ski area and snowpack in the state," says Larry Hjermstad of Durango-based Western Weather Consultants, which has run Vail's cloud-seeding operation for 29 years.
"Granted, Vail was never intended to be [scientific] research," says Hjermstad, who holds a master's degree in atmospheric science from Colorado State University. Still, he says, "we've definitely been able to find consistent results" for increased snowpack at Vail.
Ski resort officials aren't the only parties expressing interest in cloud seeding. As more people flood into Colorado and the West stretching demand for water during the longest drought in centuries and an era of unintentional weather modification, thanks to global warming scientists and Western water managers want to explore whether cloud seeding could help slake the region's thirst.
Not everyone is convinced of the merits of cloud seeding, however. A 2003 expert-panel report by the National Academy of Sciences concluded that "there is still no convincing scientific proof of the efficacy of intentional weather modification efforts."
In the absence of definitive statistical evidence, cloud seeding often is considered hi-tech weather voodoo.
Meteorological panacea Scientists at a General Electric laboratory stumbled upon the concept of cloud seeding in 1946, in Schenectady, N.Y. They discovered that dry ice shavings caused supercooled water droplets which remain liquid even at freezing temperatures to solidify into tiny ice crystals. More droplets attach to the frozen crystals until they get big enough to fall as rain and snow. The process augments precipitation, but can't conjure a storm.
Between 1949 and 1951, the U.S. military, fueled by the brainpower of the GE researchers, carried out Project Cirrus, seeding dry ice pellets into clouds around the country. When a storm from clouds seeded during the experiments covered one-fourth of New Mexico, one GE scientist concluded that the odds were "millions to one" that nature, not man, was responsible.
By the close of Project Cirrus, 30 countries around the globe had weather modification programs. The United States' Department of Defense, Weather Bureau and Bureau of Reclamation all supported millions of dollars in research and operations.
For the next few decades, researchers focused on how seeding might increase or decrease rain and snow, dissipate fog or suppress hail. Military scientists, convinced they could slow the storms or change their courses, even seeded hurricanes through Project Stormfury. Supporters billed cloud seeding as a meteorological panacea.
"I went through grad school at a time [in the 1960s] when, if you wanted to do research on clouds and storms, it had to have a flavor of weather mod," says William Cotton, a professor in Colorado State University's Department of Atmospheric Science.
While Cotton was completing his graduate and doctoral work, Colorado State professor Lewis Grant was performing a groundbreaking cloud-seeding project in Climax, Colo., a mining town near Copper Mountain Ski Resort.
Grant's research during the first half of the 1960s provided some data suggesting that seeding wintertime mountain clouds actually could increase precipitation by at least 10 percent. Grant used silver iodide, which is nearly identical in size and shape to the cloud crystals frozen by dry ice, but easier to produce and send into the atmosphere.
Based on those studies, the Bureau of Reclamation bankrolled Grant to design the five-year-long Colorado River Basin Pilot Project in the San Juan Mountains of southwestern Colorado in the early '70s. By then, the federal government was pouring $20 million a year into weather modification research, and the bureau hoped results would prove that cloud seeding could keep its reservoirs full. An estimated 10 percent increase ofsnow for southwestern Colorado would add enough water to support roughly 800,000 more people in both the Rio Grande and Colorado river basins.
Larry Hjermstad, Vail's cloud-seeding guru, was one of Grant's graduate students at CSU. After graduation, he was the contractor in charge of forecasting and seeding for the Basin Pilot Project.
The official statistical analysis of the five years' worth of research was a disappointment. Government scientists found no real difference inprecipitation between seeded and unseeded days. But after Hjermstad took a second look at the numbers, he found a "very significant result" that supported Grant's findings from Climax.
Convinced that wintertime cloud seeding could predictably enhance snowfall, Hjermstad went into business in 1976 as Western Weather Consultants and began seeding the clouds above Vail.
Tickle, tickle When the forecast calls for snow, Hjermstad calls from his office in Durango a group of Vail-area landowners who host 17 cloud-seeding generators on their properties. The machines look like file cabinets or hot-water heaters with rocket boosters attached to the tops.
After Hjermstad gives the word, a landowner walks outside and flips the generator's switch, triggering a propane tank to evaporate a solution of silver iodide. A plume of white smoke then percolates into the air, where it re-forms into ice crystals that "tickle" the storm clouds in hopes of increasing snowfall to the slopes below.
Based on dispersal patterns, Hjermstad spaces the generators five to seven miles apart, anywhere from 15 to 30 miles around Vail Mountain and Beaver Creek, both owned by Vail Resorts. From November through January, Hjermstad seeds about 20 to 30 times.
For operating the generators, the landowners earn between $1,200 and $2,500 per season. Vail doesn't disclose the full cost of seeding, but Hjermstad says it's just a fraction of the money the resort spends on snow-making.
Vail is among a small class of steady cloud-seeding clients interested in reaping wintertime powder or springtime snowmelt.
Vail spokeswoman Jen Brown writes via e-mail that based on an analysis of statewide snowfall records a few years ago, "we reached the conclusion that Vail and Beaver Creek ... were receiving 8 to 25 percent more snow in any cycle that we were seeding than the average [of] other resorts."
But even while Vail's informal snowpack measurements hint at the benefits of cloud seeding, definitive evidence is in short supply. After decades of trials, nobody is claiming with almighty statistical confidence that cloud seeding increases precipitation, or even how it attempts to do so.
Even Vail spokeswoman Brown confesses, "There's no way to determine if snowfall amounts would be the same without cloud seeding."
The downhill decline The year Hjermstad opened shop 1976 Colorado suffered an infamously dry winter. Facing a brutal drought the following summer, the state Legislature passed an emergency cloud-seeding program that then-Governor Richard Lamm called "a roll of the dice."
- William Cotton, Colorado State University professor of atmospheric science
Vail was among the ski hills, irrigation districts, power companies and water providers from every corner of the state that invested in cloud seeding.
Hjermstad and other contractors began releasing the silver iodide into the Rocky Mountain highs and made rough estimates of the effects. But because research typically costs about five times as much as seeding itself, few studies were coordinated to determine if the programs really were working.
When a series of wet years swelled the Colorado River and the West in the late '70s and early '80s, cloud seeding went out of favor, and was looked upon as pseudo-science. With statistical proof lagging and Reaganomics squeezing the federal budget, multimillion-dollar research packages disappeared. Overall federal funding for weather modification research since has dried up to about $500,000 a year.
Leaders of the National Oceanic and Atmospheric Administration "came to the conclusion that they really didn't understand enough about rain and how it happened, so they really didn't feel comfortable modifying it," says Andrea Ray, a research scientist at the NOAA Climate Diagnostics Center in Boulder.
Most ski resorts turned to more expensive but proven snow-making techniques. Farmers saved their money for crop insurance and irrigation equipment. Atmospheric scientists turned their attention to other experiments.
The 2003 report of the National Academy of Sciences reviewed every research-based weather modification assessment since the Academy's first analysis in 1964. The expert panel concluded "scientific proof of the effectiveness of cloud seeding was lacking (with a few notable exceptions, such as the dispersion of cold fog)."
Hjermstad recalls that just a few decades ago, CSU's Lewis Grant regularly received more than $1 million from the government for each seeding project. "Now, $100,000 is a big research program if you can find it," he says.
Who'll fund the rain? William Cotton is one of those researchers forwarding the study of weather modification $100,000 at a time. The CSU professor of atmospheric science wrote, with fellow department member Roger Pielke, Human Impacts on Weather and Climate, a book on cloud seeding. Cotton also has developed the Regional Atmospheric Modeling System, a computer simulation program for predicting and studying the effects of cloud seeding.
The Bureau of Reclamation gave Cotton $100,000 to use RAMS on behalf of Denver Water's cloud-seeding program during winter 2003-04. The money wasn't nearly enough, says Cotton, and the results were inconclusive.
Cotton and other cloud physics researchers face a cart-before-the-horse dilemma. Vail, utility companies and the occasional band of ranchers are ponying up the dough for cloud seeding, but no one is investing in research.
A new project in Wyoming might prove an initial step toward integrating the seeding and the research. The Equality State's Legislature has devoted $8.8 million to a five-year project to seed clouds over the Medicine Bow and Sierra Madre mountains west of Laramie.
"It does actually incorporate an experiment that is designed to be evaluated, as compared to one that is just operational," says Dan Breed, a scientist at the National Center for Atmospheric Research in Boulder, which is designing and overseeing the project.
Breed, another CSU atmospheric science department alum, says the project really isn't all that different from experiments done 30 or 40 years ago. But new technology and modeling could help deliver better results.
NCAR scientists hope to identify when to seed based on the distribution of the supercooled water droplets in the clouds and how to ensure that silver iodide released from the ground reaches the sky. The research team now is fine-tuning project specs, obtaining federal permits to place generators on government land, and experimenting with aerial seeding. The project officially will begin next winter, says Breed.
If the seeding yields the anticipated 10 percent increase in snowpack, Wyoming will reap precipitation at a cost of about $8 per acre-foot of water. Compared to reservoir construction or well development, which typically cost hundreds of dollars per acre-foot, seeding could provide a windfall of one of the arid region's most valued resources.
Wyoming's potential to invest in cloud seeding is unique, because the state is rolling in oil and gas royalties and severance taxes from mineral extraction. Meanwhile, states like Colorado weather tough economic times and tight budgets; Colorado now is thinking about a establishing a fund of just $75,000 for weather modification.
But the tide of federal funding for weather modification again might be turning. In the wake of 2005's biblical slew of hurricanes, tornadoes, floods and drought, Congress is considering bills, introduced in each chamber by Colorado Rep. Mark Udall and Texas Sen. Kay Bailey Hutchison, to create a federal weather modification research program and allocate up to $10 million a year for a decade.
Proof in the powder? At least 66 cloud-seeding programs in 10 states west of the Mississippi are aimed at suppressing hail or increasing precipitation.
"It's clear that water is scarce in the West," says NCAR's Breed. Cloud seeding should be "one of the pieces in the watershed management tool-chest."
Breed adds that projects like the one in Wyoming could convince Arizona, Nevada and California to invest in large-scale cloud seeding in upstream states, to the benefit of everyone who relies on the Colorado River for water.
Colorado State professor William Cotton says a regional seeding program could increase precipitation 8 to 10 percent throughout the river basin, but he admits that's "just a guess."
"The question is, just how much can cloud seeding do to enhance snowpack?" says Cotton, sitting in his office on Colorado State's Foothills Campus. "I don't know the answer to that, as a scientist."
The uncertainty looms like a thunderhead for environmentalists and others. Critics worry about the environmental and health effects of silver iodide falling from the sky and trickling into the reservoirs. They wonder whether cloud seeding boosts one location's precipitation while depriving another.
"If you're cloud seeding in one area, does that mean you're taking away from another area?" asks Andrea Ray of NOAA.
Jennifer Pitt, a scientist with Environmental Defense in Boulder, says expectations that seeding will prevent drought and cultivate new development in the West are disturbing. She says research has demonstrated only that weather modification might shift where rain or snow falls, not increase the available moisture.
"I'm somewhat concerned that [cloud seeding has] become a basin-wide approach," says Pitt. "By focusing on this, rather than a more practical approach of conserving water, [the states of the Colorado River Basin] are shifting emphasis on this critical issue."
Cottoninsists that seeding hasn't been linked to any adverse health effects, and he calls major shifts in precipitation between a target seeding location and a downstream area "unlikely." Lewis Grant says he's even seenweather modification cause "spillover" effects of greater precipitation indownstream places.
Just because studies haven't shown statistical evidence of increased precipitation, says Cotton, that doesn't mean seeding is impractical. Critics determined to discredit cloud seeding might as well deny global warming, too, he charges, noting that the same physics are behind both weather modifications.
He points to a study he recently completed with CSU's Israel Jirak that reveals a 30 percent decline in precipitation over the past 50 years in areas downwind of urban Denver ostensibly due to air pollution while more pristine parts of the Front Range haven't seen any reduction.
"For some reason, the scientists involved with weather modification and research are demanding an exceptionally high level of proof," says Larry Hjermstad. "They don't even require that level of proof for global warming."
And besides, can the 1.5 million riders and skiers raving about Vail's snowpack every year be so wrong?