Who'll start the rain?

China is spending millions to modify the weather for the Olympics. As 
the U.S. knows, nature doesn't bend to human will.

By Suzanne Bopp

Aug. 06, 2008 | This week, days before Sunday's opening ceremony of 
the Beijing Olympics, cannons and rocket launchers by the thousands 
will be trained on the Chinese skies. In the cross hairs: the clouds.

This is latest of China's many efforts to control the weather. China 
is probably the world's largest practitioner of cloud seeding, 
spending about $90 million a year. Last April, it claimed a major 
weather victory after seeded clouds deposited a centimeter of snow on 
the Tibetan mountains. Now, eager to ensure rain comes before -- not 
during -- the Olympics, the Beijing Weather Modification Office plans 
to seed the clouds that float by beforehand, hoping to wash the 
pollution from the air and wring out any event-delaying precipitation.

But U.S. scientists are skeptical. "China is promising something they 
can't deliver," says Bruce Boe, director of meteorology for Weather 
Modification Inc., a Fargo, N.D.-based company. "To alter a cloud's 
aerosols in such a dramatic way that it won't rain -- the cost will 
be extreme, and I don't know how to do it confidently. Nature is so 
large and powerful it can always overwhelm you." China has no 
scientific evaluations to support its promises. And, he says, it's 
just not possible to exercise such precise control over the weather.

Whether or not it's possible to exercise any control at all over the 
weather remains subject to debate. While countries around the world 
-- including the United States -- continue to fund cloud seeding in 
drought-stricken regions desperate to refill reservoirs or water 
crops, the efforts have been beset with failures and few successes 
since the very first clouds were treated.

That was in the 1950s, near the New York labs of General Electric, 
following the discovery that dry-ice shavings could convert 
super-cooled (colder than freezing) water droplets to ice crystals. 
That mattered because clouds need ice crystals (or some kind of small 
particles ) to form precipitation. Cloud seeding tries to fill that 
need. Today silver iodide -- its structure mimics that of ice 
crystals -- is most commonly used in a method called glaciogenic 
cloud seeding.

Another method, hygroscopic cloud seeding (which some scientists say 
holds the most promise today), uses materials such as salt to provide 
a droplet-attracting nucleus; it can be used in warmer clouds. Both 
methods, whether dispersed through planes or rocket launchers, need 
to start with a cloud; they can't create clouds. Cloud seeding is 
more like cloud fertilizing: It tries to make a cloud a more 
efficient producer of rain or snow.

After the discovery at GE, the company hired a plane to release dry 
ice into clouds during the winter of 1946. On the final day of the 
experiment, Schenectady, N.Y., had its heaviest snowfall of the 
season, causing GE to worry about the legal liabilities of changing 
the weather.

The initial promise of the discovery was quickly swamped by 
disillusionment. "People had all kinds of immediate aspirations that 
they could control the weather," Boe says. "But there was a lot of 
overselling. If your town had a drought, people would show up and try 
to sell this, then get out of town fast if it didn't work. That did a 
lot of damage to cloud seeding's reputation. Worldwide, that still 

While dozens of foreign countries -- Mali, Burkina Faso, Saudi 
Arabia, Indonesia and Australia, to name a few -- continue to try to 
get the weather they want, the U.S. hangs back slightly. "In other 
countries, you don't have people sitting around saying, 'We're not 
sure this works,'" Boe says.

In America, that refrain is heard frequently, but cloud seeding 
continues on the order of 60-some projects in 10 Western states a 
year, funded mainly by local and county governments, agricultural 
interests and, occasionally, ski resorts. Although the American 
Meteorological Society says some studies have shown a 10 percent 
increase in rain volume, the National Academy of Sciences has said 
there is no conclusive evidence that cloud seeding works.

It's not the initial cloud-seeding equation that is in doubt: Silver 
iodide does produce ice crystals in clouds. "You can see on a radar 
how it grows to larger particles," says Dan Breed, a project 
scientist with the National Center for Atmospheric Research. "But the 
chain of events between that and precipitation hitting the ground is 
much more complicated."

Some clouds, it turns out, are less complicated than others. Winter 
orographic clouds, which form over mountains in winter, are simpler 
to work with than convective clouds, which cause thunderstorms. 
Orographic clouds occur almost every day in the Western mountains, 
where shortages of winter snowpack (needed to fill lakes, rivers and 
reservoirs in the spring) mean extra precipitation is most often 

Glaciogenic seeding is also used for hail suppression; by providing 
many ice particles for hail to form around, it prevents very large 
hail from developing. But hailstorms are extremely complicated, Breed 
says, and experiments with hailstorms are risky. "You do a project or 
experiment and you can end up with insurance claims or crop damage," 
he says.

In Calgary and Red Deer, Alberta, insurance companies are the ones 
that have funded a hail suppression project for more than a decade, 
in an effort to reduce their damage claims. The fact that they are 
spending a couple million dollars a year on this program should be 
taken as proof that cloud seeding works, says Don Griffith, president 
of North American Weather Consultants, a Sandy, Utah-based weather 
modification company.

For insurance companies, and many other funders of cloud seeding, the 
chance of success is worth the money. That's what drove the $8.8 
million cloud-seeding project in Wyoming, initiated in part by dry 
local irrigation districts. Scientists found funding to piggyback 
research on the project, but the whole thing has hit early stumbling 
blocks, thanks to its proximity to designated wilderness areas.

To environmentalists, wilderness areas should be protected from such 
intrusions. "The most defining concept in the Wilderness Act is 
'untrammeled by man.' The idea behind cloud seeding is anathema to 
that," says George Nickas, executive director of Wilderness Watch. 
"It's hard to envision something more offensive to the idea of 
wilderness." In fact, the Forest Service's own regulations command, 
"Do not permit long-term weather modification programs that produce, 
during any part of successive years, a repeated or prolonged change 
in the weather directly affecting wilderness areas."

Nevertheless, the project has proceeded, with minor modifications: 
The silver-iodide-releasing generators are to be placed outside, not 
inside, the wilderness areas. That's not a satisfying solution for 
the protesters -- it will still introduce more pollution.

"Under that same logic, if I wanted to dispose of toxic waste, I 
could do so to my heart's content on Forest Service lands as long as 
I dumped the stuff out of an airplane instead of packing it in on 
horseback," Jonathan Ratner, Wyoming director of the Western 
Watersheds Project, wrote in a statement. Part of his concern is what 
would come with increased rainfall over the forest -- increased 
pollution. Rampant gas and oil development in Wyoming has raised 
emissions several-fold; rain could bring that out of the sky into the 
water and cause nitrification.

Neither protests nor the deep discomfort about changing the weather 
has translated to a glut of weather-modification-related lawsuits. No 
doubt that's partly due to the fact that a plaintiff seeking damages 
would have to prove the cloud seeders were responsible for the 
harmful weather, and causation is as difficult to prove for attorneys 
as for scientists. It's not uncommon to hear the complaints that 
someone's cloud seeding stole someone else's rain. But scientists 
point out that that's also impossible to prove.

A bigger worry is that cloud seeding might be having the wrong 
effect. "Right now there's no guarantee, but we might be spending 
time and money and reducing precipitation," says Colorado State 
University atmospheric science professor William Cotton.

U.S. funding for research to answer such questions remains paltry. 
Down from a high in the late 1970s of $20 million, today less than 
$500,000 goes to cloud-seeding studies. Because studies are lengthy 
-- it takes about 10 years to look at weather trends -- even those 
that get funding often run out before the study is complete. Bills 
currently moving though Congress seek to establish a national 
weather-modification program, but such bills have been introduced, 
and disappeared, before.

This time around, there may be renewed interest, courtesy of climate 
change, which presents some of the same fundamental questions as 
weather modification. Scientists are more interested than ever in 
learning how we're already changing our weather, perhaps to learn how 
to change it back.

It seems certain we've altered precipitation patterns in measurable 
ways. "We're finding aerosol pollution reduces precipitation in 
orographic clouds," Cotton says. "It introduces very small particles, 
and they all compete for the same amount of water. Pollution means 
huge numbers of particles, so it's hard to go in and seed clouds that 
are polluted."

Over the past few decades, pollution seems to have decreased 
precipitation considerably, especially in the West, where clean ocean 
air passes over polluted urban areas before moving inland. In the 
Sierra Nevada mountains, the loss is estimated at 3.2 million acre 
feet (an acre foot covers an acre of land in water 1 foot deep) each 

Can we learn to seed polluted clouds so we can get that precipitation 
back? What about the effects of changing temperature? We know low 
clouds tend to have a cooling effect on earth, and high clouds create 
warmth by absorbing more long-wave radiation. Could we use some of 
these effects to alter not just the weather but the climate itself?

Such climate engineering could be the next hot topic among 
atmospheric scientists. "We may have no choice," Cotton says. "Twenty 
years down the road, if the warming trend has increased enormously 
and half of Florida is underwater, politicians will say, 'Do climate 
engineering.' Doing something is better than sitting on your hands. 
If, at that point, we don't have the scientific knowledge, and we 
introduce the technology, we could find ourselves in the middle of an 
ice age. We won't be able to figure this out that fast."

Attempting such a strategy would raise all of cloud seeding's 
questions -- of control, unintended consequences, environmental 
effects -- to a new order of magnitude. But we need to start looking 
at it now, Cotton says. "If politics take control, and we don't have 
a science basis, who knows what could happen?"

-- By Suzanne Bopp