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"If (proof) exists, we're looking for a rather small needle in a huge haystack of hay. You don't even know what it looks like, you don't even know what success would be," he said. That's not to say the techniques were disproved, either. A March 2007 study for the California Energy Commission by the U.S. Bureau of Reclamation found that cloud-seeding programs statewide produced 300,000 to 400,000 acre-feet of water annually. The water, mostly in the form of melted snow, benefits agriculture and the state's hydroelectric power industry. It also augments recreational and municipal supplies. To make or mitigate rain, target clouds are injected with chemicals such as silver iodide, which has a crystalline structure almost identical to ice, or with dry ice, which changes the clouds' structure. Braham recalls watching the transformation take place from aboard research aircraft. "Dry ice is most effective. You just crush it up and spew it out. A hole will develop in the cloud," within about 10 minutes, Braham said. "It's always mesmerizing to see this change." The chemical transforms water droplets, which cause a cloud's opacity, into ice crystals. That leaves a clear patch which, over time, fills in. As for China's Olympic feat, Braham said it would be nice if the experiment was run and published prior to the big day so it could be weighed on its scientific merits. Otherwise, he, for one, would award the gold medal for weather to Mother Nature.
Irene Klotz's blog: Space Diary Larry O'Hanlon's blog: Earth Impacts |
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