Cloud seeding, a method of weather modification, is gaining attention as countries seek to increase rainfall. This technique, which has been in use for over 80 years, involves using planes and drones to release compounds such as silver iodide into clouds. These compounds aim to form ice crystals that grow large enough to fall as rain or snow.
In August, residents of Homer, Alaska, were not widely alerted to an experiment conducted by San Francisco start-up Rainmaker, which used cloud-seeding technology. The company claims this experiment produced 19 million US gallons of water in the sky over three hours.
Cooper Freeman, Alaska director of the Center for Biological Diversity, expressed scepticism about the safety of the compounds used for residents and the environment. He noted a lack of downstream monitoring to verify the environmental impact of silver iodide.
Rainmaker's founder and CEO, Augustus Doricko, stated that the company releases silver iodide at 20 grams per flight, distributed across thousands of square kilometres. He claims the resulting increase in concentration on the ground is in the parts per quadrillion, which is below the FDA's allowable threshold.
More than 50 countries are developing programmes to modify weather, and new start-ups are emerging in the field. However, these businesses continue to face questions regarding the safety and efficacy of their methods. Researchers are also exploring new seeding agents, such as a protein made from amino acids, which is being tested as a potentially safer and more efficient alternative to silver iodide.