We have known for 75 years that it is possible to convince stingy clouds to offer up a little more rain or snow when we need it most. And today, as the American West faces drought after drought, we really do need it.
But the extent of scientific knowledge about the effects of specific cloud seeding efforts isn’t a lot better now than it was when a high school dropout and self-taught chemist named Vincent Schaefer conducted the first ostensibly successful experiment in cloud seeding by releasing six pounds of dry ice into a cloud over Mount Greylock, Massachusetts, on Nov. 13, 1946.
“It seemed as though the cloud almost exploded,” Schaefer wrote on that day.
“Seemed” was the operative word, both then and now. For the ephemeral nature of clouds and the dynamic nature of weather makes it very hard to know, with any degree of certainty, just how well cloud seeding works in any specific place. These vast unknowns make this a tremendously exciting area of exploration.
A recent article in The Salt Lake Tribune tapped into that excitement. The article noted that Utah has one of the most extensive cloud-seeding programs in the world — and this is true. However, it also suggested that “every major mountain range in the state now sees extensive cloud seeding” and that these efforts are so effective, compared to other states, that “Utah doesn’t have as much room for growth because there are fewer gaps in its seeding program.”
In fact, there is likely lots of room for growth — but to get there, we need to start with science.
Although it has long been the subject of speculation and debate, we do know that seeding can lead to a quantifiable increase in precipitation. Other research efforts have helped us better understand the conditions under which seeding might be most effective in specific geographies. And recent research has suggested that high-resolution weather models and complex statistical techniques can be applied to evaluate the effectiveness of cloud seeding programs — meaning the future could be a very prosperous time for “moisture farmers.”
These studies have offered ample direction for the evaluation and potential improvement of Utah’s seeding program. But while an earlier report recommended “a critical review to identify a feasible and robust approach” to cloud seeding in this state, such an effort has not yet been undertaken.
Utah’s ground-based cloud-seeding program relies on generators that release microscopic particles into clouds to act as a nucleus for ice crystals to form. Because this process works best once those clouds reach a mountain barrier, where rapidly lifting and cooling winds help turn clouds into snow, the precise location of these generators is of the utmost importance. Without a baseline, scientific study of the generators’ effectiveness as currently situated, though, there is no way to know whether the program’s performance might be improved by moving the generators to more suitable locations.
Likewise, there has been virtually no exploration of the effectiveness of airborne seeding on Utah’s clouds. Ground-based seeding may ultimately prove to be not only more effective but more cost effective, but that has yet to be established in a rigorous study.
Research from Utah State University and the Utah Climate Center suggests that a majority of precipitating clouds may be suitable for seeding, but that suitability varies greatly from mountain to mountain, month to month and weather system to weather system. The research also suggests that some mountains have gained seeding suitability and others have lost it — and that these changes will continue in coming decades under various climate warming scenarios. So far, though, Utah’s investment in operational cloud seeding has not been aligned to these nuanced variabilities.
Finally, and quite excitingly, new research from the University of Utah suggests that the compound we most commonly use for seeding might not be our only choice. Silver iodide has a crystalline structure similar to frozen water and this property has made it the primary substance used in cloud seeding since a chemist named Bernard Vonnegut (yes, he was the brother of novelist Kurt Vonnegut) first suggested its use the day after Schaefer’s dry ice experiment. But organic substances, such as the naturally occurring compound known as phloroglucinol, have been shown to be quite good at helping start the process of ice crystal formation, and discoveries such as these eventually may lead to an even more effective alternative to silver iodide.
There are nearly unlimited opportunities to explore and evaluate ways to make Utah’s cloud seeding program more effective. And, indeed, some fledgling efforts are underway. Lower Basin states, along with Utah Division of Water Resources, are working together to support scientific research into cloud seeding from the Utah Climate Center — but the center has not yet begun a scientific evaluation of the impact of seeding in Utah.
With sufficient funding, this could be a tremendously exciting time of discovery in the field of cloud seeding. And given the vast need for water in the West, it seems the time is right for this research and development investment. But that effort should not be led by what seems to work; it should be led by science.
Binod Pokharel
Matthew D. LaPlante
Simon Wang
Valeria Molinero
Binod Pokharel is a post-doctoral researcher in the Utah Climate Center at Utah State University, where Matthew D. LaPlante is an associate professor of journalism and Ph.D. student in climate science and Simon Wang is a professor of climate science. Valeria Molinero is a distinguished professor of physical and materials chemistry at the University of Utah.
