How can stakeholders, legislators, lobbyists, and misguided farmers fall for something so blatantly obvious? Cloud seeding is NOT working to materially increase our water supply. How did we get here?

For starters, tunnel vision and a complete disregard for any evidence contrary to the narrative does not help form an educated opinion. But then we also have the reality of no positive results in water gains, and it becomes apparent that Idaho water policy is following the settled science of cloud seeding - a belief, not fact.

Case Study 1: Colorado Project

Great Expectations: A Review of the Colorado River Basin Pilot Project (CRBPP)—The Nation’s Most Expensive Randomized Orographic Cloud-Seeding Experiment

• Two of the three experiments, Climax I and Wolf Creek Pass, claimed increased snowfall on seeded days. A later analysis revealed these were Type I statistical errors (lucky draws of naturally stronger storms). The third experiment had data‑handling errors that created the illusion of success. Thus, the CRBPP was trying to replicate results that were random and not reproducible.

• Earlier studies assumed that the temperature at 500 hPa (T500) reliably indicated cloud‑top temperature (TCT). This turned out to be false (cloud‑top temperatures vary rapidly and unpredictably). The CRBPP’s seeding decisions were based on this flawed assumption.
  Later airborne and ground measurements showed much higher natural ice concentrations, meaning seeding would have little or no effect.

• Silver iodide was released from ground‑based generators, but stable air layers frequently trapped the particles near the surface. On many days, the seeding agent never reached the clouds, making effective seeding impossible.

Insightful questions

These questions remain unanswered:

“How did so many pages of faulty literature concerning the cloud-seeding successes in the central Rockies reach the peer-reviewed literature?”

“Wasn’t the finding by the experimenters that seeding had made nonprecipitating clouds precipitate exactly like natural clouds, a red flag?”

“Do reports of cloud-seeding successes need extra scrutiny compared to standard literature?”

In the latter case, and based on this review of the CRBPP, we think so. A quote by Dennis (1980, p. 176) makes a similar point: “The recent changes in thinking about [the Climax experiments] emphasize the desirability of basing conclusions about cloud seeding effectiveness on the total body of available evidence, rather than on whatever randomized projects enjoy the favorable attention of atmospheric physicists in a particular year.”

Case Study 2: Idaho SNOWIE

There are plenty of other caveats from the study, Tessendorf says. In SNOWIE, planes sprayed silver iodide into more than two dozen clouds that looked ripe for seeding. “But they could only draw a clear link between seeding and snowfall in three cases. There’s a small, hard to pinpoint signal that cloud seeding created additional ice in a handful of other cases. And then no signal at all in some instances.

Figuring out which clouds will respond to seeding and which will not is still an open question. Plus, she says, the study was limited based on geography, only seeding clouds in southern Idaho. The clouds there are without a doubt different from clouds in other parts of the West, she says.

“It’s a complicated problem and the results that we see in one cloud will not automatically apply to every cloud everywhere,” Tessendorf says.

But those scientific blind spots haven’t stopped states and water agencies from investing in the technology. The University of Wyoming’s Jeff French says water leaders should know gaps remain in our understanding of how well cloud seeding works.

“The evidence is pointing into the direction that it does have an impact and we can increase snowpack,” he says. “But I’m skeptical still when I hear people say 10 to 15 percent because that number to me is something that is difficult to justify.”

The researchers offer conservative estimates, but the stakeholders appear to be more bullish in their marketing materials.

Idaho Power cloud seeding webpage states:

Idaho Department of Water Resources (IDWR) states:

Note: IDWR brochure references the Colorado program.

Furthermore, IDWR 2023-24 Winter Season End of Season Report shows percent normal precipitation.

Going Forward

The co-author on the first case study above also provides these statements in The Cloud Seeding Literature and the Journal Barriers to Faulty Claims: Closing the Gaps.

Arthur L. Rangno, retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.

Goals

Honest researchers admit there are too many unknowns in the science of cloud seeding to claim it is rigorously tested. Some might confess that it is inherently incompatible with the scientific method when considering natural variability. But in Idaho there is no turning back. Poorly drafted resolutions (117 and 118) calling cloud seeding sophisticated makes it clear that most* Idaho legislators are all in on the pseudoscience.

* A follow up article will expand on a few good legislators willing to ask questions and read the science. Hats off to them.

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