Scientists see no value in cloud seeding

National Academy finds no proof it makes rain

October 14, 2003|By KNIGHT RIDDER/TRIBUNE

WASHINGTON - The nation's top scientists have confirmed the adage that everybody talks about the weather, but nobody can do much about it - even though states, cities and utilities are spending millions of dollars trying.

Attempts to make it rain by seeding clouds are increasing worldwide, with 66 such efforts under way in the United States, mostly in the parched West, but there's no scientific evidence that it works, the National Academy of Sciences concluded yesterday.

In 10 states and two-dozen countries, meteorologists are seeding clouds, usually with silver iodide, in an effort to unleash more rain and snow. But the attempts are much like those of a desperate cancer patient taking unapproved drugs based on hope and belief rather than science, according to University of Virginia atmospheric scientist Michael Garstang, the chairman of the academy's study panel.

"To some extent weather modification is an act of faith with people," said panel member Robert Serafin, president emeritus of the National Center for Atmospheric Research in Boulder, Colo. "In terms of precipitation on the ground, there's no compelling evidence."

While some statistical studies show an increase in rainfall after cloud seeding, weather-modification efforts demonstrate no concrete repeatable effects, Garstang said.

Officials in the multimillion-dollar weather-modification industry insist they get results but say it's difficult to meet the academy's tough standards.

The American Meteorological Society's official position is that there has been some statistical evidence showing a 10 percent increase in precipitation after cloud seeding, but no conclusive cause and effect. It doesn't recommend seeding clouds to end droughts.

California has 12 current cloud-seeding projects; one over the San Joaquin River has been going since 1950. Texas, Kansas, Oklahoma, North Dakota, Colorado, Wyoming, Idaho, Utah and Nevada also have cloud-seeding projects. China spends $40 million a year on it.

For the most part, there's no proof that any of it works, with one exception: Cold fog, which is uncommon, can be dissipated by seeding clouds, the academy said in its 123-page report.

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