Residents of Homer, Alaska, were unaware that a cloud-seeding experiment was conducted over their heads on August 23, according to reports. San Francisco startup Rainmaker claims its operation dispersed 19 million gallons of water in the sky within three hours using cloud-seeding technology.
Cloud seeding, a weather modification technique developed over 80 years ago, involves using aircraft or drones to release compounds like silver iodide into clouds. These compounds encourage the formation of ice crystals, which can eventually grow large enough to fall as rain or snow. The process essentially accelerates the natural condensation of water vapor within clouds, leading to precipitation.
Cooper Freeman, Alaska director for the Center for Biological Diversity, expressed concern that local residents were not adequately informed about the experiment. He also questioned the safety of the substances used and their potential impact on the environment and local habitats. "It doesn't appear that there was any downstream monitoring to verify that this silver iodide didn't impact the environment," Freeman stated.
Freeman further suggested that cloud seeding is a distraction from addressing urgent water conservation issues, especially in light of global water scarcity. The United Nations Secretary-General António Guterres recently noted that the world is using freshwater faster than it can be replenished, a sentiment echoed by reports indicating the driest period for global rivers in over three decades.
While cloud seeding can increase precipitation, its effectiveness is limited. The 19 million gallons dispersed by Rainmaker, for instance, equates to approximately 0.01 inches of rain over 100 square miles. Despite these limitations, over 50 countries are developing weather modification programs, and numerous startups are emerging with new technologies for rain generation.
Augustus Doricko, founder and CEO of Rainmaker, addressed concerns about the chemical safety of silver iodide. He explained that the company releases 20 grams of silver iodide per flight, spread over thousands of square kilometers, resulting in ground concentrations in the parts per quadrillion, which he asserts is far below FDA-approved thresholds.
Rainmaker utilizes drones to deliver silver iodide flares into clouds, a process that requires the presence of clouds to be effective. The burning flares atomize water particles, allowing them to remain suspended in freezing clouds and eventually form rain. The company operates in states such as Idaho, Utah, and Colorado, as well as in Jordan, where water scarcity is a significant issue.
The history of cloud seeding dates back to 1946, with early experiments using dry ice. Silver iodide was later found to be more effective. While early seeding efforts showed limited impact, a 2017 study provided evidence of silver iodide's efficacy using radar and precipitation gauges.
Jon Meyer, an assistant state climatologist at the Utah Climate Center, noted that with optimal conditions, cloud seeding can yield an additional 5% to 10% of precipitation. He expressed encouragement regarding innovations like those from Rainmaker, particularly the use of drones for more targeted cloud-seeding operations.