Back in 1946, cloud seeding was used as a way to increase rainfall by meteorologists at General Electric's laboratories in Schenectady, N.Y., but after 60 years, scientists are wondering if it actually works.
Study results on cloud seeding are starting to trickle in and researchers found that droplets of silver iodide do increase precipitation by 5 to 15 percent, according to Live Science.
Winter clouds in western states have been injected with silver iodide for decades by water providers, power companies and ski areas. Snowfall can make up 70 percent of annual precipitation in some areas.
"Critical Issues in Weather Modification Research," a 2003 National Research Council report, said "there is still no convincing scientific proof of the efficacy of intentional weather-modifications efforts," according to Live Science.
The problem, the report stated, was "the absence of adequate understanding of critical atmospheric processes that, in turn, leads to a failure in producing predictable, detectable and verifiable results."
Researchers in Wyoming conducted a $14 million randomized, blind experiment designed and evaluated by the National Center for Atmospheric Research (NCAR). For six winters between 2008 and 2014, storms were seeded over the Sierra Madre and Medicine Bow mountain ranges. While a storm over one mountain range was seeded, the other was left as the control. If the storms were moist and lowered mountaintop temperatures to less than 17 degrees Fahrenheit (minus 8 degrees Celsius), they were seeded.
Only 118 storms were seeded over the seven winters, although researchers had expected 60 to 70 storms per year, according to Live Science. A report was still released to the Wyoming Water Development Commission stating that seeded storms did not significantly increase precipitation.
Researchers are not giving up on cloud seeding that easily. Since there were not a great number of storms to analyze, scientists studied the snowmelt. Snowmelt added to streamflow which gave researchers reason to believe that cloud seeding yielded a 5 to 15 percent increase in precipitation, according to Live Science.
Cloud seeding is still considered an inexpensive way to provide water, though the research hasn't changed many minds. "It confirms what we already thought," said Thomas Ryan, of the Metropolitan Water District of Southern California. The Metropolitan Water District delivers drinking water to 19 million people.
Brad Udall, from the Colorado Water Institute, was less impressed. "It's in the modeling that they get these higher numbers of 10 to 15 percent," he told Live Science. "These statistics still aren't very good."
