Humans have been trying to control the weather since the day we traded in our spears for shovels. Cultures from every corner of the globe have worshipped rain-granting deities, and our sci-fi villains have been obsessed with flood and drought. But in the modern era, we no longer have use for the old water gods. We've got the technology, finally, to make the clouds do our bidding.
That's not to say that the transition from praying for rain to manufacturing rain was an easy one, or even that the current methods are the most effective possible. The history of weather modification, the act of intentionally manipulating the atmosphere, has had its fair share of charlatans and crackpots. You may have guessed that, considering this scientific school has grown out of pure superstition.
Cloudbusting Was a Bust
The most famous weather modification quack has got to be Austrian psychoanalyst Wilhelm Reich. Like L. Ron Hubbard without the cult, Reich performed dozens of scientifically unsound experiments throughout the '50s and '60s, which resulted in highly questionable results not well-regarded by the mainstream scientific community.
Reich's weather modification techniques were among his most absurd attempts at innovation. He used a series of hollow tubes, like a giant metal pan flute, attached to flexible metal hoses at their rear, which were in turn attached to slightly smaller hollow metal tubes whose open ends are dipped in a pool of water. This contraption supposedly harnessed "orgone energy" from the water and attracted it from the atmosphere, converting it into moisture. Sort of like a lightning rod, but bullshit.
Cloud Seeding: The Atmosphere's Test Tube Baby
Cloud seeding is the opposite of cloud busting. For one thing, it's a real thing. The process has been replicated numerous times both in the lab and in the field and is backed up by years of peer-reviewed scientific research. For another, it impregnates clouds to instigate the precipitation process rather than magically gathering them using dark energies.
Cloud seeding is currently used all over the world — including throughout the United States, China (where it is used to clear smog in Beijing), India and Russia — to enhance precipitation, both rain and snow, while inhibiting hail and fog. And it actually works.
Cloud seeding takes effect by spraying microscopic particles like aluminium oxide or silver iodide to affect the development of condensation by acting as artificial ice nuclei. They effectively give ice crystals something to grow on. The downside of cloud seeding is that it requires that the surrounding air already contain a certain percentage of water vapour; you can't make something from nothing.
The particulate method, specifically using silver iodide, was discovered by none other than Dr Bernard Vonnegut, Kurt Vonnegut's brother, in 1971. Since Silver iodide has a similar crystalline structure to ice, it forms an artificial reef of sorts for ice crystals to grow on.
Vincent Schaefer, however, is credited with discovering the principles of contemporary cloud seeding in 1946. After a hike up New Hampshire's Mount Washington with Nobel laureate Irving Langmuir, Schaefer developed a supercooled cloud system (where the liquid water vapour is at most 0C) out of a deep freezer in his lab in order to study the effects of ice crystal growth in a variety of mediums from talcum powder to table salt to top soil. The cloud for these experiments consisted of a large breath of air exhaled into the freezer. However, on one hot summer day, the freezer simply couldn't work hard enough to get the chamber sufficiently cold, so Schaefer helped the process along, dropped some dry ice in there, and promptly discovered a way to instantly transform supercooled water vapour into ice. Further experiments successfully replicated the effect, with -40 degrees C as the transformative limit for supercool liquid water.
Unlike silver iodide, which gives the crystals somewhere to start, the dry ice method simply drops the temperature low enough to incite spontaneous crystallisation while producing a vapour supersaturation. They're typically delivered by aircraft, which light silver iodide flares as they fly through clouds, or by ground-based delivery systems like Howitzers and anti-aircraft guns.
Though dry ice and silver iodide are the two primary methods of cloud seeding, liquid propane and table salt are also used. Salt has proven especially effective in warmer clouds, such as those in Mexico and South Africa, because the salt crystals cause larger droplets to form than otherwise would and precipitate out of the cloud more readily.
America's cloud seeding efforts are well documented. In the sweltering summer humidity of Alexandria, Virginia in 1948, mayor Carl B. Close ordered a cloud seeded with dry ice and was almost immediately rewarded with 22mm of rain — during a drought. And while international treaties now forbid using weather modification for war, from March 1967 through July 1972, the US military's 54th Weather Reconnaissance Squadron carried out Operation Popeye, an extensive cloud-seeding effort to extend the monsoon season over Vietnam in the hopes of miring the Ho Chi Mihn Trail for an extra 30 - 45 days a year. The squadron's motto: "Make mud, not war."
The UAE's Ionizers: Tearing the Sky a New One
The United Arab Emirates is a land rich in wealth but poor in precipitation. That's why president Sheikh Khalifa bin Zayed Al Nahyan has had the nation's top scientific minds secretly toiling for years to create a new means of weather manipulation that would work more effectively in the region's extreme temperatures. The result: the biggest Ionic Breeze on Earth.
Ionic Breeze devices are giant ionisers mounted atop tall steel poles and were built by the Swiss company, Metro Systems International. The devices generate massive ionic fields, positively charged ions ground back to the Earth while the negatively charged ions rise into the atmosphere. As they rise, the negative ions (electrons) collect particles of dust on the way up. These flecks act as seeds for ice crystal formation, much as silver iodide does except without the need for clouds. As long as the atmospheric humidity is at least 30 per cent, the system supposedly works even in clear skies.
In the summer of 2010, 100 such emitters were spread over five sites in the Al Ain region. During July and August alone, when the area typically receives zero rainfall, it reportedly rained on 52 separate occasions, often with gusting winds and sometimes hail. The Max Planck Institute for Meteorology monitored the project and backed the study's findings. This could be huge for the Middle East, where water is often in short supply and desalinisation plants are nine-figure investments (and another eight-figures a rear to run). The ionisers reportedly only cost $US10.5 million to build and $US8.9 million a year to operate.
Atlanta and the Clean Air Act
But why spend all that money when you can just curb air pollution to the same effect? That's what Atlanta did.
When the Clean Air Act went into effect in 1970, nobody could have possibly foreseen the immediate and incredible effects it would have on the environment. In the first five years following the bill's enactment, small particle emissions (under 10 micrometers) decreased by 40 per cent nationwide. In the following two decades the average rainfall in Atlanta jumped 10 per cent and stayed there.
Turns out the air pollution caused by Atlanta-area factories in the '50s and '60s resulted in less efficient clouds. That is, the small particle size of the pollution was great for forming clouds, but terrible at creating precipitation. For that, you need larger particles as well. "You don't want tons of little ones, which is what Atlanta had in the '50s and '60s," Jeremy Diem, a climatologist at Georgia State University, told Scientific American.
The Sky's the Limit
During its hosting of the 2008 Olympics, China went far beyond a grandiose opening ceremony. The PRC reportedly had 30 airplanes, 4,000 rocket launchers, and 7,000 anti-aircraft guns on the ready to obliterate any potential precipitation. This raises more than a few technical and ethical questions, like "what are the environmental and pathological consequences of spraying large amounts of silver iodide into the atmosphere?" and "If China can stop rain on a whim for the Olympics, what's to keep them (or any nation) from weaponising that ability?"
On the other hand, there is also significant upside to our methods of weather control beyond just making it rain. Many of the same techniques can be used, for instance, to mitigate the destructive force of hurricanes.
Overall, while weather modification techniques can be hit or miss, the future of the science looks promising. With advances in large-scale systems modelling and atmospheric research, we may soon be able to control the weather with the touch of a button. And that's when the real fun begins.