Science: Careful Rainmaker

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When scientific rainmaking was invented in the U.S. in the late 19405, it seemed that at last man could do something about the weather. All over the world, commercial rainmakers armed themselves with Dry Ice or silver iodide, set to work seeding clouds wherever they could find local governments or groups of rain-hungry farmers willing to pay them. But over the years, not enough rain fell to support the reputation of the rainmakers. Rainmaking slipped into disrepute.

Last week a persistent scientist named Edward George Bowen was proving that rainmaking can be notably successful when conducted as a long-range program with carefully limited goals. As chief of the Radiophysics Division of the Australian government's Commonwealth Scientific and Industrial Research Organization, Dr. Bowen was put in charge of Australian rainmaking more than ten years ago. By careful and skeptical investigation he soon discovered why most efforts had been failures. The commercial rainmakers' favorite method (because it was the cheapest) was to spray silver iodide into the air from ground generators. Dr. Bowen found by actual experiment that ground-generated silver iodide seldom reaches the clouds. He proved further that silver iodide somehow can become inactivated as a rainmaker after less than one hour of exposure to the atmosphere; when it does reach the clouds from the ground, it is usually too old to be effective.

Bowen began a study of Australia's weather almost cloud by cloud. He dispensed his silver iodide from generators on airplane's wingtips, learned by repeated experiment what kinds of clouds could be wrung out. Then, backed by the Australian government, he started a long series of carefully controlled experiments in the Snowy Mountains of New South Wales.

His conclusions are calculatedly sober. Dr. Bowen's figures show that seeding by airplane achieved approximately 20% increase in the amount of rain that fell on the test region. For $225,000 a year, he estimates, he can drop extra rain worth $2,200,000 on a hydroelectric watershed.

The Australian public, forever haunted by fear of drought, has followed Bowen's program with enthusiastic appreciation. When a long dry spell last month threatened to ruin wheat planting in the Darling Downs district of Queensland, the parched farmers clamored for Bowen's rainmakers. He sent airplanes reluctantly, knowing he could promise added rain over a period of months—not cloudbursts on order. Even when seeded clouds obligingly dropped heavy rain on several large areas, Bowen refused to claim credit. Nevertheless he smiles a little when he hears of his growing reputation among grateful farmers. "There's no doubt," he says, "that we are starting to push nature around a bit."