Weather modification is the act of intentionally manipulating or altering the weather. The most common form of weather modification is cloud seeding, which increases rainfall or snowfall, usually for the purpose of increasing the local water supply. Weather modification can also have the goal of preventing damaging weather, such as hail or hurricanes, from occurring; or of provoking damaging weather against an enemy, as a tactic of military or economic warfare like Operation Popeye, where clouds were seeded to prolong the monsoon in Vietnam. Weather modification in warfare has been banned by the United Nations under the Environmental Modification Convention.
History A popular belief in Northern Europe was that shooting prevents hail, which thus caused many agricultural towns to fire cannons without ammunition. Veterans of the Seven Years' War, Napoleonic Wars, and the American Civil War reported that rain fell after every large battle. After their stories were collected in War and Weather, the United States Department of War in the late 19th century purchased $9,000 of gunpowder and explosives to detonate them in Texas, in hopes of condensing water vapor into rain. The results of the test, supervised by Robert Dyrenforth, were inconclusive. Wilhelm Reich performed cloudbusting experiments in the 1950s, the results of which are controversial and were not widely accepted by mainstream science. In November 1954 the Thailand Royal Rainmaking Project (Thai: โครงการฝนหลวง) was initiated by King Bhumibol Adulyadej. He discovered that many areas faced the problem of drought. Over 82 percent of Thai agricultural land relied on rainfall. Thai farmers were not able to grow crops for lack of water. The royal rainmaking project debuted on 20 July 1969 at his behest, when the first rainmaking attempt was made at Khao Yai National Park. Dry ice flakes were scattered over clouds. Reportedly, some rainfall resulted. In 1971, the government established the Artificial Rainmaking Research and Development Project within the Thai Ministry of Agriculture and Cooperatives. In January 2011, several newspapers and magazines, including the UK's Sunday Times and Arabian Business, reported that scientists backed by the government of Abu Dhabi, the capital of the United Arab Emirates, had created over 50 artificial rainstorms between July and August 2010 near Al Ain, a city which lies close to the country's border with Oman and is the second-largest city in the Abu Dhabi Emirate. The artificial rainstorms were said to have sometimes caused hail, gales and thunderstorms, baffling local residents. In the run up to the 2008 Beijing Olympic Games, the Chinese Government said they could control precipitation to some extent and that the Games would not be hampered by bad weather conditions. For this purpose they established a government office called the Beijing Weather Modification Office, which is under the national weather control office.
Cloud seeding
Cloud seeding is a common technique to enhance precipitation. Cloud seeding entails spraying small particles, such as silver iodide, onto clouds to attempt to affect their development, usually with the goal of increasing precipitation. Cloud seeding only works to the extent that there is already water vapor present in the air. Critics generally contend that claimed successes occur in conditions which were going to lead to rain anyway. It is used in a variety of drought-prone countries, including the United States, China, India, and Russia. In China, there is a perceived dependency upon it in dry regions, and there is a strong suspicion it is used to "wash the air" in dry and heavily polluted places, such as Beijing. In mountainous areas of the United States such as the Rocky Mountains and Sierra Nevada, cloud seeding has been employed since the 1950s. Project Cirrus was an attempt by General Electric to modify the weather which ran from 1947-1952. During that time, under the supervision of the United States Air Force, attempts were made to create snowstorms and seed hurricanes by using silver iodide. While General Electric reported positive results, they also acknowledged that their experiments were controversial. The United Arab Emirates has been cloud seeding since the 2000s and aims to increase rainfall by 15-30% per year. The materials used are potassium chloride, sodium chloride, magnesium, and other materials.
Consequences
Societal Not having adequate systems to handle weather modification may have disastrous consequences. "In the city of Jeddah in Western Saudi Arabia was damaged by floods in 2009 that reportedly killed more than 100 people; igniting questions of why the country doesn't have effective drainage systems in place."
Human The U.S. National Library of Medicine notes that the silver iodide has no known "ill effects" on people, although people's "hands may have remained yellowed for weeks" after being exposed to it.
Storm prevention
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