A change in the weather

Hurricanes. Drought. Crop-crushing hail. Multi-car pile-ups on fog-shrouded highways. These are a few of the perils that might be prevented, or at least curbed, if the sci-fi dream of human-induced weather modification can become reality.

In the last half-century, weather modification — the practice of using cutting-edge technologies to sway the weather — has enjoyed varying levels of public popularity and financial support. In the late 1970s, the United States invested more than $20 million a year on this type of research, but it now spends less than $500,000 annually.

Mike Garstang is working to assess — and perhaps reverse — that falloff. Garstang, a distinguished emeritus research professor in environmental sciences at U.Va., chaired a committee of weather experts gathered this year by the National Academies’ National Research Council. The committee issued a report calling for a renewed look at the possibilities of weather modification.

“It’s been 30 years since the last definitive report was done on weather modification,” Garstang said. “As you can imagine, a lot has happened technologically and scientifically in that time.”

Advances have improved scientists’ ability to observe the weather, accumulate and assess large quantities of data and simulate weather processes using mathematical models. But because funding for weather-modification research has dried up, the advances have not been applied to influencing the weather.

The notion that scientists could modify the weather to human benefit first took hold in the 1940s. Researchers hoped that by seeding clouds with silver iodide they could alter the structure of the clouds to a desired effect — they could make ground fog disappear; they could make it rain.

“That was a very dramatic idea,” Garstang said, “but simplistic. The early optimism — it was too optimistic — led to a lot of dissent. Some were saying, ‘Wait, you can’t do this.’”

The believers pressed on, using a range of modification methods to trigger rainfall. Ground generators can be rigged to send plumes of silver iodide wafting up into the clouds. Aircraft can seed the clouds by flying through them or above them and releasing the agent. A third method, used by Russian scientists, calls for artillery shells laced with silver iodide to be fired into the clouds.

But as the decades passed, the rift between the believers and non-believers remained. “There was a polarization between those who believed you could modify weather and those who believed you couldn’t,” Garstang said. “Those who believed repeatedly failed to demonstrate their belief scientifically. They failed to present clear physical evidence.”

If weather modification were someday perfected, the benefits could be tallied in dollars and cents. “The loss to crops from hail damage is about $2.5 billion a year in the U.S.,” said Garstang. “If you could mitigate the hail, if you make it fall out when it’s still small, it’s less damaging.”

Weather modification could be used in other beneficial ways: to clear fog off crowded interstates, to moderate hurricanes, to make rain fall during favorable weather conditions so the water can be stored for use during periods of drought. For many, it’s a life-and-death matter: nearly 2 billion people around the world face severe water shortages, and this number is projected to increase to over 3 billion during the next 25 years, according to the National Academies.

The report from Garstang’s committee calls for a coordinated national program to answer fundamental questions about atmospheric processes and address other issues that impede progress in weather modification. The report may serve as a wake-up call to those who doubt the promise of this type of research.

“Whether we like it or not, humans are modifying the atmosphere,” Garstang said, pointing to global warming as an example of unintentional weather modification. “We should spend just as much effort on intentional modification.”