The Science Behind Human-Controlled Weather

It hasn't been an enjoyable winter for much of the United States. Record snowfall has blanketed cities like Boston, while below-freezing temperatures and relentless wind chills have sent shivers all the way from Chicago to Atlanta.

At times like these, some people start wondering whether humans can combat the cold in ways other than by wearing layers and cranking up the heat. What if, one daydreams, we could break apart the clouds that produce rain and snow and wintry mixes? What if we could control the weather for once?

It's possible—sort of. The process of weather modification comes up in conversation again and again, often in debate (over who—governments or private companies—should do the modifying, what the health effects might be, etc.). Usually, it comes up simply when we're in need of better weather.

Like on wedding days, for example. The U.K.-based luxury company Oliver's Travels has announced a weather-modification service that would burst clouds and guarantee clear skies by using cloud seeding, a process that encourages precipitation, before their clients' big days. The company only requires three weeks to study and alter the weather at the wedding site—and $150,000 in payment.

The announcement baffled Bruce Boe, the vice president of meteorology at Weather Modification, Inc., a North Dakota-based company that researches and carries out cloud seeding for farms in need of rainfall. I reached out to Boe, who has studied storms and flown aircrafts since 1974, to find out whether cloud seeding could in fact create sunny skies—and by extension, reverse winter freezes in the future.

Looking over the Oliver's Travels package, Boe told me it's impossible to guarantee perfect weather. "We don't believe there's a way to reliably prevent precipitation," he said. "We're a little surprised someone else thinks they can."

There are too many obstacles to controlling the weather, he explained. Only some clouds allow for successful seeding, and weather patterns have remained difficult to predict, even with the help of our best forecasting instruments. The scale of the Earth's atmosphere is far too great to tamper with—at least for now. (Oliver's Travels didn't respond to an interview request, but the company says in a blog post that "new technology and research have produced reliable results that make cloud seeding a dependable activity.")

Most important, cloud seeding can only produce so many forms of precipitation: Glaciogenic seeding creates ice by using a nucleating agent (silver iodide, which attracts water) to accelerate a cloud's development. Hydroscopic seeding involves jumpstarting droplet formation and making droplets bigger, leading to rainfall.

"Think of it as applied cloud physics," Boe said. "It's not really modifying the weather, but modifying the precipitation processes in clouds."

In fact, even the scientists who invented cloud seeding quickly realized total weather modification would be too far-fetched a goal. In 1946, the General Electric chemist Vincent Schaefer experimented with creating precipitation, using dry ice to form crystals. He then worked with Bernard Vonnegut—yes, Kurt's brother—to develop silver iodide, that compound that increased the size of water droplets and induced rain and snow indoors. They were excited enough at the start: In a 1993 interview with the American Meteorological Society, Schaefer recalled how he felt during his successful dry ice experiment:

It was a very warm, humid day and I was using my chamber very actively... I decided to cool it down by putting some dry ice in it. And the instant the dry ice got into the supercooled cloud, everything was ice crystals. So I could see I had the answer. It was a serendipitous event... I knew I had something pretty important.

I demonstrated this at a number of scientific meetings, and everybody got quite excited about it. Harry Wexler [the then-chief scientist for the U.S. Weather Bureau] came up to me, and said, 'You know, about 10 years ago I was calibrating thermometers in a cold chamber using dry ice, and I wasn't smart enough to realize I had something important.' Because he had everything I had, but he just didn't observe.

As research moved forward, however, Schaefer and Vonnegut saw weather modification become less about modifying weather and more about enhancing it. "At first, they thought, 'Ah, we're going to be able to control the weather,'" Boe said. "We've learned since then that, well, it's not as possible as we thought."

Even so, because of its science-fiction-like possibilities (controlling the weather is a superpower, after all), weather modification has always led to aspirational inventions and promises of clear skies. Boe cited hail cannons, which claim to stop hailstorms by generating shockwaves. They've been used often throughout Europe since the early 20th century, but have no evidence of actually suppressing hail.

That's not to say the decades since Schaefer and Vonnegut's dry-ice experiments have been for naught. Though complete weather modification may never be possible, Boe explained the technology involved has leapt forward. In 1978, for example, he navigated planes through clouds without GPS and used carbon-dioxide pistols to catch cloud droplets on glass slides. He had to later bring those slides to a lab, where he could examine them under microscopes.

Today, he uses optical array probes, diodes, and lasers that show in real time the size, shape, and number of particles in a cloud while he flies. And before taking off, he can simulate the cloud seeding to select the right clouds. It's not only more efficient, but more accurate as well. Which, as Boe put it, helps him and his team understand weather patterns and cloud science first, before they can tackle the possibilities of complete weather modification.

"We're pushing ahead on all these fronts, and it's an exciting time to be in the field," he said. "I'm just still waiting for the day when we quit calling it 'weather modification,' and start calling it what it is: cloud modification."