Cloud seeding

Cloud Seeding is a weather modification technique used to improve a cloud's ability to create rain or snow. This is done by using electrical charges or artificially adding particles of dust or salt, called condensation nuclei, to the atmosphere, allowing water droplets or ice crystals to form and increasing the chances of precipitation. The technology has been used to increase chances of rain and snowfall, with the hope that it can be used to tackle issues of extreme heat and drought.

Cloud seeding has its origins in the 1940s, with General Electric researcher Vincent Schaefer credited as the first person to conduct cloud seeding experiments. Much of Schaefer's work during and after World War II focused on preventing aircraft from icing over while in flight. Schaefer had designed a special homemade freezer to better grasp how ice crystals are formed within clouds.

One day, upon entering his lab, Schaefer discovered that his freezer had been turned off and placed a block of dry ice inside of it in an attempt to cool it as quickly as possible. This caused a cloud of ice crystals to form in the air. Schaefer continued experimenting and conducted the first cloud seeding test by aircraft in 1946. Flying over the Adirondack Mountains in New York, Schaefer dropped six pounds of crushed dry ice into a cloud, causing snow to begin falling almost immediately.

A diagram showing how cloud seeding works. Source: Santa Barbara County Water Agency.

US government-led research into cloud seeding continued for several decades. In 1947, a collaboration between GE and the US government called Project Cirrus was created with the goal of manipulating hurricanes with cloud seeding. The results of the study were deemed inconclusive and scientists concluded that it was not effective. A similar project attempted to boost rainfall in western states in the 1960s, with similar mixed results. The US government also experimented with using weather manipulation as a weapon of war in the 1960s and 1970s with Operation Popeye, which attempted to create enough rainfall to disrupt enemy supply routes during the Vietnam War. An international treaty banned this in 1977.

The past decade has seen a sort of renaissance in cloud seeding projects in the United States. As of 2021, at least eight states, including Colorado, California, Utah, Wyoming, New Mexico, Arizona and Nevada, actively conduct cloud seeding programs. However, there is still much debate among the scientific community concerning how effective cloud seeding actually is. Many point to the fact that research has yet to prove whether or not cloud seeding actually produces more precipitation than would have naturally occurred.

Some progress towards more conclusive results was made in January 2017 with the creation of the SNOWIE project (short for "Seeded and Natural Orographic Wintertime Clouds) in Idaho. Based off of research from the 2008 Wyoming Weather Modification Pilot Project, the SNOWIE project seeded a group of clouds in the Idaho River Basin on January 19, 2017 during weather conditions that were deemed "ideal" for seeding—the sky was cold and cloudy, but had not produced any precipitation. Over the course of three days, SNOWIE project planes dropped sodium iodide into the clouds, finally causing them to produce snow. The study provided some of the first quantitative evidence available for cloud seeding's effectiveness.

In July of 2021, the United Arab Emirates used cloud seeding to create more rainfall in Dubai after temperatures there reached 115 degrees fahrenheit. The technology differs from traditional cloud seeding techniques in that scientists used electrical charges from drones, not sodium iodide, to seed the clouds and produce rainfall.