Weather modification has a reputation problem.It was banned as a weapon of war by the United Nations in 1978. It has sparked concern over the potential for ‘rain theft.’ And scientific confidence that it truly works has always been scattered. Even so, a number of countries, like China and the United Arab Emirates, and U.S. states, like Texas and Arizona, have thrown their weight behind cloud seeding—a form of geoengineering that involves planting molecules in clouds that encourage water droplets to clump together and fall as rain—as a tool for combating drought, averting storms, and keeping hydro power plants running. The lattermost is what meteorologists at Idaho Power, the state’s electrical utility, are doing to keep the state off fossil fuels. Seventy-six percent of utility-scale electricity produced in-state comes from renewables, and most of that from hydro. The utility estimates that cloud seeding generates enough water to keep the lights on in around 74,000 homes. “Cloud seeding is just another arrow in the quiver,” Derek Blestrud, senior atmospheric scientist at Idaho Power told Motherboard in a new video. “It’s just another tool that we can use in the whole portfolio of the water system and our portfolio of power generation.” While the UAE’s National Center of Meteorology garnered controversy this year for hinting at its use of cloud seeding to break up long periods of drought during summer, Idaho Power openly seeds its clouds during winter. By launching silver iodide—a compound that mimics the structure of ice molecules and gloms onto them, weighing them down until they fall—into clouds during colder conditions, the utility triggers snowfall. This ensures that snowpack near the state’s river basins reach the volumes required to melt come summer time, keeping the state’s hydropower plants running.Blestrud and his team are confident that the practice works, despite a long history of doubt around its efficacy. Determining causality in weather patterns is difficult without a control variable: It’s notoriously difficult to test what a cloud would’ve done had it not been seeded. But the body of evidence to support the effectiveness of cloud seeding has grown in recent years, thanks in part to the work of researchers like Katja Friedrich. An associate professor in atmospheric and oceanic sciences at the University of Colorado Boulder, Friedrich recently published a paper that traced lines of snowfall to the pathway taken by their cloud-seeding jet. “We could really track the entire lifecycle of this process, from putting the silver iodide into the cloud and then the cloud converting from a liquid cloud into a snow cloud,” Friedrich told Motherboard. “We saw these lines, they look like zigzag lines. We thought, 'OK, this is nothing that nature can produce.’”
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