Cloud seeding to prevent drought
Blowing dust, swarms of grasshoppers, and not enough hay to feed the starving livestock. For Prairie farmers, drought can be disastrous. But it's not just the farmers who suffer — a severe drought in Western Canada can hurt the entire Canadian economy. From the devastating dustbowl years of the Great Depression to some of the more recent Prairie dry spells, CBC Archives explores the history of drought in Western Canada.
• Precipitation can only occur when ice crystals form in the clouds and grow large enough to fall to earth as rain, snow or hail. If ice crystals don't form, there won't be any rain. The key to cloud seeding, then, is to get those ice crystals to form. The difficulty is that the droplets of water in clouds are "supercooled," which means they remain in a liquid state at temperatures well below 0° C.
• To turn water droplets in clouds to ice crystals, clouds are shot with either dry ice or silver iodide, both of which are capable of freezing the supercooled droplets. The most efficient way of seeding the clouds is by dropping the cooling agents (silver iodide is the most common) from an airplane onto the top of a cloud.
• Cloud seeding is also used to reduce the size and incidence of hail. Cloud seeding is believed to have the power to produce rain before the droplets grow large enough to turn to hailstones.
• There was a flurry of international research and experimentation with cloud seeding during the 1960s and '70s. In Canada, the Alberta Research Council carried out cloud seeding experiments from the mid-1950s to the mid-1980s. But this program proved controversial for a few reasons: many scientists found no conclusive proof that cloud seeding really worked, while some farmers even complained that too much rain was ruining the hay. The Alberta program was discontinued in 1985.
• In an effort to reduce insurance claims from hail damage, insurance companies on the Prairies later brought back cloud seeding to reduce the amount of hail-related damage. In 2002, the National Post reported that a group of Alberta insurers paid nearly $1.58 million to an American company called Weather Modification Inc. for a cloud seeding program. The insurance companies said hail-related claims went down 45 per cent as a result.
• During the height of the 2002 drought, CBC Television in Edmonton reported that Alberta farmers were taking another look at the viability of cloud seeding to help with drought. While many were ready to try anything that might help, B.C. meteorologist Phil Austin was still unconvinced that cloud seeding worked: "Anything is possible. It is possible the cloud seeding is working. What is difficult to assess, as the years change, is whether the effect we're seeing is due to climate change, for example."
• As of 2004, Alberta insurance companies were still using Weather Modification Inc.'s cloud seeding to reduce hail. Cloud seeding is also still commonly used in other countries, including the United States, although there remains a great deal of controversy over whether it's useful or not.
• Weather modification isn't the only method modern science has been experimenting with to deal with drought. Scientists around the world have also been working toward developing drought-resistant (or drought-tolerant) crops. This process requires isolating the genes that allow certain plants to survive dry conditions, and using those genes to genetically modify crops like wheat, grains, corn and soya. A lot of progress was made toward isolating such genes in 2003 and 2004.
Program: Shragge's Journal
Broadcast Date: Jan. 15, 1981
Guest(s): John Maybank, Henry Zilm
Host: Sherv Shragge
Last updated: May 31, 2013
Page consulted on December 6, 2013
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