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
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
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
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
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 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 happens."
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
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
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
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
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