While attempting to control the weather might sound like science fiction, countries have been seeding clouds for decades to try to make rain or snow fall in specific regions. Invented in the 1940s, seeding involves a variety of techniques including adding particles to clouds via aircraft. It is used today across the world in an attempt to alleviate drought, fight forest fires and even to disperse fog at airports. In 2008, China used it to try to stop rain from falling on Beijing's Olympic stadium. But experts say that there is insufficient oversight of the practice, as countries show an increasing interest in this and other geoengineering techniques as the planet warms. The American Meteorological Society has said that "unintended consequences" of cloud seeding have not been clearly shown or ruled out " and raised concerns that unanticipated effects from weather modification could cross political boundaries. And there have been instances when cloud seeding was used deliberately in warfare. The United States used it during "Operation Popeye" to slow the enemy advance during the Vietnam War. In response, the UN created a 1976 convention prohibiting "military or any other hostile use of environmental modification techniques". A number of countries have not signed the convention. Researcher Laura Kuhl said there was "significant danger that cloud seeding may do more harm than good", in a 2022 article for the Bulletin of the Atomic Scientists.