Tag: weather modification

The Why of the Storm

The Why of the Storm

whyofstorm coverMany researchers have concluded that climate change is feeding extreme hurricanes, and amplified concerns could bring about the second coming for weather modification. A computer simulation from a Colorado State University professor could be the future of the field — and the federal government’s contingency plan for looming hurricane disasters.

The feature got a mention on a climate-change blog of the journal Nature, and also earned a third-place award for science reporting from the Colorado chapter of the Society of Professional Journalists.


The Why of the Storm

Could polluted hurricanes save the world?

By Joshua Zaffos

Rocky Mountain Chronicle, June 14, 2007

The year is 2025, and a Category-5 hurricane is barreling toward the Atlantic coast. If the storm continues on its present course, forecasters predict a 15-foot storm surge, flooding houses along the coast from Charleston, South Carolina to Washington, D.C. With just 72 hours until landfall, FEMA doesn’t call for an evacuation: Instead, a fleet of C-130 cargo planes takes off from Andrews Air Force Base in Maryland and flies into the storm, loaded with a megaton payload of Saharan Desert dust.

Cue Wagner’s “Flight of the Valkyries” as the pilots open the payload doors over the hurricane. As if sprinkling pixie dust, the maneuver tames the weather system: Within a day, the rains diminish, the winds let up, and the storm is downgraded. Tragedy is averted.

“If you could reduce the intensity by 40 knots, you could save billions in reduced damages,” says Bill Cotton, a Colorado State University professor of atmospheric science, who collaborated with University of Illinois researchers to simulate the dirt-dumping scheme using
the Regional Atmospheric Modeling System, or RAMS, a program Cotton developed with CSU professor emeritus Roger Pielke Sr.

Cotton is seeking federal funds to pursue his theory. With strong financial backing, he estimates that field studies of his dust-busting hurricane treatment could start within 10 years.

Almost 60 years after government scientists first began discussing the idea of toying with the weather, the field of weather modification is again in vogue. Western states are considering cloud seeding — loading clouds with silver iodide — to amp up regional precipitation in order to keep shrinking reservoirs full. And Colorado U.S. Rep. Mark Udall plans to reintroduce legislation that would create a federal weather modification bureau.

Many researchers have concluded that climate change is feeding extreme hurricanes, and an amplified fear of more Katrinas could bring about the second coming for weather modification. Cotton’s simulation could be the future of the field — and the federal government’s contingency plan for looming hurricane disasters.

But, then, just because something can be done doesn’t mean it should.

Slowing the Skater

Inside the CSU Atmospheric Sciences Building, Stephen Saleeby is at a loss to describe the workings of Cotton’s atmospheric modeling program. RAMS simulates the formations of clouds and storms based on a variety of conditions, such as regional wind speed, relative humidity and temperature. Saleeby, a research associate of Cotton’s, says programming isn’t quite as simple as plugging in a few numbers and then clicking the mouse to see how the simulated weather plays out.

The model consists of tens of thousands of lines of code. Saleeby can run some basic simulations on his desktop computer, but the larger analyses of hurricane pathways or cloud-seeding operations are handled through a cluster of up to 20 processors. One of Saleeby’s projects, studying the development of the Southwest monsoon season, takes the clustered computers three days to process.

RAMS allows Cotton, Saleeby and others to forecast how altering weather systems might affect snowfall, the duration of a drought, or a hurricane’s response to plane-loads of fine dust.

Such modeling has become highly sophisticated since the field of weather modification was born 60 years ago, when General Electric scientists discovered that silver iodide could increase precipitation in clouds. Researchers thought they could boost rain and snowfall and suppress hail and tornadoes.

The federal government began spending millions of dollars on a national weather modification program in 1959, partly motivated by the Cold War and the Soviet Union’s successful space launch of Sputnik two years earlier. The U.S.S.R. might have first dibson outer space, but the U.S. government wanted control of the atmosphere and the weather. From 1967 through 1981, the federal government never spent less than $9.9 million a year on weather modification. The bill topped out at $18.7 million in 1972.

Researchers conducted hurricane reduction experiments under Project Stormfury starting in 1962. Stormfury scientists seeded three hurricanes
in the 1960s but weren’t able to consistently affect the storms. A treatment of Hurricane Debbie in 1969 coincided with a 30 percent drop in the storm’s wind speed, but scientists couldn’t conclude that natural factors didn’t account for the results.

In the case of hurricanes, researchers assumed that dropping silver iodide onto specific storm clouds would cause “supercooled” water droplets to freeze. That process would create latent heat on the storm’s edge and, according to the theory, slow its speed.

“We use the analogy of the spinning skater,” says William Woodley, a federal researcher in Miami during the ’60s and ’70s, who flew into hurricanes to conduct experiments for Project Stormfury.

Whirling ’round and ’round, a figure skater pulls her arms into her body, turning faster and faster. That might help a performer score a few extra tenths of
a point from the judges, but out in the ocean, it’s the type of development that turns a tropical storm into
a hurricane — and then a major hurricane. Weather modification, as attempted through Stormfury and now modeled by Cotton, coaxes the hurricane to stick out her arms and slow down.

“The instrumentation wasn’t all that [in the 1960s]. The modeling was crude,” says Woodley, now a Littleton-based weather modification consultant. Another significant part of the problem was that Stormfury’s theoretical assumptions didn’t pan out.

Cloud-seeding experiments to augment precipitation for farming proved similarly disappointing. When adverse events, like floods or blizzards, coincided with modification projects, citizens blamed the government. People also faulted drought in one region on cloud seeding in an adjacent area. Federal research dollars began to taper in the late ’70s, and the cash flow stopped completely after 1985.

Today, weather modification is strictly a private and/or academic affair, but even without government cash, the improvements in computer modeling have advanced the field.

“What I can do today, I couldn’t even have dreamed of in graduate school,” Cotton says.

In Dust We Trust

Researchers are still trying to slow down the whirling skater, but the simulation, put forth by Cotton and his University of Illinois colleagues, uses a new technique, different from Stormfury’s.

In the simulation, tiny dust particles are dropped onto the storm. Very small raindrops form, which are less likely to collide in the clouds and more likely to evaporate before they fall, cooling the air. The upshot is a tamer storm: Wind speeds decrease 50 knots after the dust particles are introduced in the simulation. In the case of Katrina, a dust drop could have mellowed the storm at its fiercest point from Category-5 to Category-2 on the Saffir-Simpson scale.

“[This] is much more powerful than anything that was considered back in the Stormfury days,” Cotton says, sitting in his office, photos of heavy and ominous clouds hanging on the walls.

The theory has natural inspiration: African dust, which can impede the formation of tropical storms before they move across the Atlantic.

“We’ve observed that if a big dust storm comes along [in Africa], that tends to weaken a storm,” Cotton says.

A similar simulation by professor Daniel Rosenfeld and Woodley, also just published this year, produced the same results through the release of “submicron hygroscopic” — extremely minuscule and moisture-attracting — particles. Rosenfeld now has a provisional patent on the process, Woodley says.

Airlifting a desert dust storm sounds like a massive operation. The million-dollar question is, How much dirt are we talking about, and what’s that going to do to a coastal city?

Cotton can’t give a specific amount of dirt. That’s
one of the next steps after
he receives more funding.
But the delivery of the dust specks — each so small that 100 million of them could fit on a penny, Cotton estimates — would be a logistical issue and would require a convoy of cargo aircraft, like the C-130s.

Not to worry, Cotton says. A storm “would rain out the crud before it hits shore.”

In terms of clouding the
sky, the amount of dust is
roughly equivalent to the pollution levels of a major urban city, Cotton adds. It would be
as if a hurricane were to rev through the Atlantic and then pass through downtown St. Louis.

Pollution is the Solution

African dust pollution isn’t the same as the haze that hangs over a city, but the particles in the air act the
same. Cotton and his associates have titled their peer- reviewed article, soon to appear in The Journal of Weather Modification, “Should we consider polluting hurricanes to reduce their intensity?” The title is purposely provocative: According to most climate scientists, manmade pollution is already tinkering with the weather.

Auto exhaust and coal-fired power plant emissions
are already poking and prodding at the figure skater. (In another study, Cotton and graduate students observed that increased urban pollution from vehicles and coal-fired power plants have coincided with — and seemingly caused — decreased precipitation along the Front Range.) The collective impact of this pollution, contributing to melting glaciers and warming oceans, unfortunately, doesn’t deter the hurricanes. In fact, it makes them more persistent.

Scientists have found that warming sea-surface temperatures are causing more ferocious hurricanes, like Katrina and Rita, although that particular correlation isn’t quite as definitive as other impacts of human-caused climate change.

Recent studies by researchers at MIT, Woods Hole Oceanographic Institute, and the National Center
for Atmospheric Research (NCAR) in Boulder have concluded that warming oceans will cause fiercer hurricanes, though not necessarily more storms.

“We think global climate change will cause more intense hurricanes and, in particular, much heavier rainfall,” says Kevin Trenberth, head of NCAR’s Climate Analysis Section and a lead author on several reports by the Intergovernmental Panel on Climate Change (IPCC) that affirm global warming is occurring.

“The debate, if any, is the cause [of more intense hurricanes],” Trenberth says, although “the IPCC has very clearly stated that global warming is occurring and anyone who disagrees has their head in the sand.”

Still, there are other researchers who say historical hurricane records can’t be compared with modern monitoring. Also, factors like wind shear — the difference in wind speed at varying heights — and massive deviations of the ocean-atmosphere system, like El Niño, play key roles in hurricane development and intensity. Therefore, we shouldn’t presume that recent hurricane seasons are abnormal or unprecedented, or that climate change is the cause.

Cotton downplays the link between more intense hurricanes and climate change as “a lot of arm waving.”

It’s almost shocking to find that someone who has
dedicated his life to figuring out how to modify the weather, including methods that simulate urban pollution, is unconvinced that we’re unintentionally changing the climate.

Cotton says he is, indeed, a “climate skeptic,” and even calls the projections of the IPCC, put forth by 600 scientists, “back of the envelope numbers.” The skepticism lands him in the company of a more notorious
and outspoken skeptic, CSU’s hurricane- forecasting guru William Gray, whose office is around the corner from Cotton’s.

“I don’t think we can say with scientific confidence that current trends are due to human activity,” Cotton says. “I’m not buying into the warming trend being influenced by humans.”

After years of studying clouds and the atmosphere, and trying to change the weather, Cotton says he hasn’t seen enough evidence that rising global temperatures are anything more than “natural variability” of the planet.

“My involvement with weather modification, I take that skeptical view,” Cotton says. “I’m a modeler by trade, so that makes me very skeptical of models, including my own.”

But Cotton qualifies his uncertainty: On a scale from negative ten (being a staunch climate- change doubter) to ten (being a firm believer), Cotton rates himself as a negative one or a negative two, and Gray as a negative seven.

“I just think the jury’s still out, but I’m trying to find out the other side,” Cotton explains. “But I try to stay away from the personality issues.”

The irony here is that any renewed interest in weather modification, including the possibility of federal funding for the practice, is clearly tied to fears of how climate change might lead to longer droughts, bigger floods and wilder hurricanes. Colorado Congressman Mark Udall has twice introduced legislation
to establish a federal weather modification program that could draw millions of research dollars and put the government back in the cloud-seeding and hurricane-taming business. Udall plans to reintroduce the bill again
this congressional session (Sen. Kay Bailey Hutchinson of Texas has sponsored the same bill in the Senate during past sessions, as well).

The Ethical Storm

We can no longer claim that everyone is talking about the weather, but that no one is doing anything about it. We are doing something, whether we mean to or approve of it.

“Weather modification is a reality,” says Woodley, the former Stormfury scientist in Littleton. “Forget about anything I might do deliberately. We humans are changing the weather [with pollution]. My question is, If we’re doing this inadvertently, why can’t we do this — if we have our wits about it — advertently?”

That’s one of the questions Connie Uliasz has considered carefully over the past few years. Uliasz is completing her master’s thesis, “Ethical Issues in the Use of Weather Modification Technologies,” through CSU’s philosophy department.

“You’re probably talking to the world’s expert on the ethics of weather modification,” she says, half-jokingly.

Uliasz is properly schooled for that title. Her undergraduate background is
in philosophy, and she has studied with well-known CSU bioethicist Bernie Rollin and, to a lesser extent, Colorado State professor Holmes Rolston, “the Father
of Environmental Ethics.” She also has experience in atmospheric sciences, and at CSU, she has worked with Bill Cotton and helped manage professor Scott Denning’s “BioCycle” climate
change research group.

“I spent a long time
trying to understand the
science, years of that,
before I could even start
with the ethics,” Uliasz
 says. Few researchers ever attempt a cross over. “They” — scientists — “don’t even think about ethics,” she charges.

Weather modification is at an ethical disadvantage on several counts, Uliasz says: “There’s some good evidence it actually works, but it’s difficult to prove, and you don’t know what you’re going to get [in terms of experiment results]. And you’re not going to solve questions in the long run.”

Weather modification, Uliasz continues, can “sidetrack people from really making the hard decisions. It’s almost a red herring of a technological fix. And Americans, especially, love their technological fixes.”

Americans also have a Category-5 fear
of hurricanes in the haunting aftermath of Katrina. Our broken-levee blues may be out of proportion compared to our concerns over other risks, like coastal flooding.

A March 2007 Gallup survey shows 49 percent of Americans fear more intense hurricanes from global warming, and we’re more worried about another climate- change-fueled hurricane than drought, flood, an increased prevalence of disease, or a loss of coastal areas.

This year’s hurricane season started before its usual June 1 date, when Subtropical Storm Andrea formed in May. Hurricane forecasters, like CSU’s Gray,
 are projecting that this year could turn
out a lot like 2005, and if another Katrina, or even an Andrew or a Hugo, rocks the Atlantic coast, Congress will only be more inclined to consider a quick fix. But instead of slowing down the skater, maybe we should concentrate on encouraging her not to spin faster.

“It seems like it could be better to spend [federal] money when hurricanes come, instead of trying to disperse them,” Uliasz says, the ethical coin flipping inside her head. “But, then, if Katrina were a Category-2 instead of a 5, we’d still have New Orleans. I don’t know how many more really awful hurricanes we could have before we say, ‘Let’s try anything.’”

Snow Job

Snow Job


Rocky Mountain Bullhorn, DATE (also published in Colorado Springs Independent, DATE)
By Joshua Zaffos

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.

A ground-based iodide generator used for cloud seeding.

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.

Tickling the clouds

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.”

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.”

Cotton insists 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 seen weather modification cause “spillover” effects of greater precipitation in downstream 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?