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By Tom Standage

If the US Air Force is to be believed, illegal drugs aren't going away anytime soon. In fact, in the future they'll only cause more problems, because the distributing cartels will have consolidated. They'll have wealth, political power, and, instead of a few guys with submachine guns, entire armies.

Picture, then, a South American cartel of the mid-2090's. It maintains hundreds of fighter planes, thwarting attacks by launching a dozen Russian- and Chinese-made aircraft for every one of ours. Our sole advantage comes from a piece of military intelligence: Cartel pilots won't fly in harsh weather. But this doesn't mean waiting around for the skies to turn - because by then, thunderstorms will be made to order.

First we launch uninhabited aerospace vehicles (UAVs), which, through advanced cloud-generation technology, disseminate cirrus clouds to block enemy surveillance. Next we seed any one of the daily rain showers passing through the region, intensifying it precisely over the target. Then we snuff out our blinded enemy.

Over the course of the next century, the weather will be our most powerful weapon. So says Weather as a Force Multiplier: Owning the Weather in 2025, part of a 1996 Air Force-commissioned report forecasting the technology required to maintain US air and space leadership into the next century. "Current technologies that will mature over the next 30 years will offer anyone who has the necessary resources the ability to modify weather patterns, at least on the local scale," the study says. "Weather modification can provide battlespace dominance to a degree never before imagined. By 2025 it will be within the realm of possibility."

Sound like hyperbole? Ironically, three years after the report was issued, that's what Air Force officials would have you think. "We have no plans to try and modify the weather. It's just too much of a crapshoot in terms of the complex dynamics and huge energy involved," says Brigadier General Fred P. Lewis, the Air Force's director of weather. "How will you guarantee the outcome? How will you create what you want yet avoid kicking off an undesirable or even dangerous weather system?"

Made-to-order thunderstorms, says the military, "can provide battlespace dominance to a degree never before imagined."

Whatever the truth about the military's attitude toward weather modification, the private sector won't wait for Lewis to answer his own questions. One sign of real-world progress has come in a rather ancient-sounding technology: cloud seeding. Introduced in the 1940s, the tactic has made huge leaps of late thanks to a new method known as hydroscopic seeding. In the early '90s, South African researchers began using flares shot from planes to inject water-attracting salts into clouds. In these and other tests, hydroscopic seeding has shown evidence of increasing not only the amount of rainfall, but also the duration and vertical concentration of individual storms.

The most extensive hydroscopic test to date, being conducted in Mexico by scientists from the National Center for Atmospheric Research in Boulder, Colorado, has been running for three years. So far, 99 seeding missions have shown rainfall increases of as much as 40 percent, according to head researcher Brant Foote. Another 50 tests with the same results, Foote says, and he'll consider the evidence conclusive.

While Foote and the military talk of weather enhancement, some of the most important developments are coming in weather suppression. One factor pushing those developments is the ever increasing density of Earth's population. Not only does it amplify the need to move water to drought-afflicted areas, it also intensifies the amount of damage natural disasters wreak. Weather-related catastrophes caused $92 billion in damage worldwide during 1998 and displaced more than 300 million people from their homes, according to the Worldwatch Institute in Washington, DC. Top priority: Mother Nature's ultimate terror, the hurricane.

Hurricanes are fueled by the evaporation of warm ocean water. One way to kill a storm would be to cool the ocean. Given the huge energy investment of, say, towing icebergs, however, researchers have made little progress in this regard. Pushing a hurricane toward land would also kill the storm by eliminating its energy source - but also threaten people and property. That's not an option, of course. But can we make a hurricane think it's over land?

A team of MIT scientists believes so. Led by professor Kerry Emanuel, the scientists are hoping that by applying a chemical coat one molecule thick to the ocean's surface, they can retard the natural heat-transfer process that occurs during evaporation, which would slow the storm. Team member Moshe Alamaro tests materials by pouring tiny amounts of various biodegradable, oily substances into a special test rig filled with seawater. To see how this monolayer material would stand up in the ocean, he agitates the water with a paddle wheel. It's an arduous process. "There are 10,000 types of oil, all with different properties," he says. "We need to have something with a diffusion rate faster than the rate at which waves break, a film that will repair itself quickly."

Using oil to suppress evaporation could also help protect reservoirs. That prospect has attracted attention from Chevron, which has supplied a number of possible monolayer materials and shown an interest in giving the MIT group startup funding. But the team's real hope is one day to spread a monolayer over several hundred miles of ocean in the path of a hurricane, stopping it before it can reach land.

Tom Standage (tomstandage@economist.com) is a science correspondent in London with The Economist.

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