Tinkering with clouds

Federal funds for weather-modification research have dried up as well. According to Colorado State University atmospheric scientist William Cotton, federal dollars for weather modification research peaked at roughly $19 million a year in the 1970s. They dropped to less than $5 million a year during the '90s, and now hover at about $500,000.

The field has entered what Dr. Cotton calls the "dark ages," where weather-modification programs are forging ahead with little or no scientific research programs to back them. The efforts are driven by dwindling groundwater supplies in many parts of the world, along with the demands growing populations are placing on rivers and reservoirs.

Yet, some analysts say, the science behind climate and meteorology has advanced to the point where weather modification deserves another, closer look.

"We know so much more about the physics, and computer modeling is so much better, that it's time to revisit the subject," says James Baker, former head of the National Oceanic and Atmospheric Administration.

Before leaving office, Dr. Baker commissioned a National Research Council study on weather-modification science and future research needs. The results are due by April.

In the meantime, researchers are finding funds where they can. Hoffman, for example, has drawn funding from the National Aeronautics and Space Administration's Institute for Advanced Concepts in Atlanta for modeling studies he and his colleagues have been carrying out on hurricane Iniki. "We're not aiming to eliminate hurricanes, but to control their paths so they do not strike population centers," he says.

Initial results in a "proof of concept" simulation suggest that Iniki could have been nudged sufficiently with one-time changes in sea-level temperatures and winds roughly 30 hours before landfall. To trigger those changes artificially in one shot, however, "would take way too much energy.... It's unrealistic," Hoffman acknowledges.

He adds, however, that any operational system for steering severe storms would likely make several less energy-intensive changes as time progresses. A second round of modeling now under way is aimed at more clearly identifying the energy needs such efforts might require.

MIT's Dr. Emanuel notes that while some of the approaches to delivering or removing the energy needed to shift weather systems are exotic, they needn't be.

Even a 1 degree Celsius change in temperature can have a large effect over time, he notes. That change could be achieved by having aircraft lay out "black contrails" - thin manmade clouds - roughly 600 miles long and 60 miles wide to cool the atmosphere beneath by obscuring sunlight.

Yet as researchers weigh the scientific and technical aspects of large-scale weather modification, they remain mindful of its two-edged nature.

Hoffman notes that during the Vietnam War, the US military seeded monsoon clouds in Operation Popeye in an attempt to use weather to hamper troop and supply movements along the Ho Chi Minh Trail. When information about the program was declassified in the mid-1970s, the international community established the UN Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques.

Several scientific bodies, such as the WMO and the US American Meteorological Society, have issued cautionary policy statements on weather modification.

But Hoffman notes that a broader discussion is needed as technologies emerge that make large-scale weather modification possible. "If these trends continue, in a few decades we'll have all the parts we need to put a system together."

The ethical and legal implications are vast, he says. "Any change in weather helps some people and hurts others. Cost versus benefit is a difficult question. Is this something we want to do?"

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