China is notorious for having some of the worst air pollution in the world. Images of dense, miasmic smog engulfing its most polluted cities are a common sight. The country has made significant progress in combating air pollution, but it remains a problem in many areas.
In light of these pollution concerns, it was reported earlier this month by the South China Morning Post that the Chinese government had used a weather modification technique called cloud seeding to clear air pollution over Beijing before the country’s Communist Party celebrated its centenary in July. The technique involves using an aerial vehicle like a plane or drone to deploy a compound into the clouds (most often silver iodide) to trigger condensation of water in the air. It leads to rain or snow—which inevitably helps to rid the atmosphere of the nasty pollution particles.
The artificial rain, Chinese researchers would later learn, actually reduced air pollution over the city by more than two-thirds, and nudged the air quality index from moderate to good. For the crowd watching the military flyover and 100-gun salute at Tiananmen Square, the sky looked a bit better than it had for a while.
Cloud seeding might seem completely outlandish on a first glance, but it's far from science fiction—and its star is only on the rise. China previously used cloud seeding during the 2008 Beijing Olympics to reduce smog. Manipulating the weather like Storm from X-Men actually has some utility in remediating some of today’s climate problems.
But Katja Friedrich, an associate professor in atmospheric and oceanic sciences at the University of Colorado, Boulder, told The Daily Beast that using it to clear pollution isn’t necessarily the most effective plan, and China might be misguided into believing this is a reliable long-term solution.
“Rain does get pollution out of the air. There’s no question,” Friedrich said. “But I think it’s easier to solve the air pollution problem than to try to solve it after the fact with cloud seeding.”
In fact, cloud seeding’s most impactful applications are less about pollution and more about drought. The American West is facing a historic drought, so many Western states like Arizona, California, Colorado, and Wyoming have embraced cloud seeding as a way to hopefully keep crops alive and maintain water supplies. The United Arab Emirates unleashed a fleet of cloud-seeding drones this past summer to help residents in Dubai beat the heat. China recently announced plans to develop an expansive cloud-seeding system over the next decade to produce artificial rainfall over 224,00 square miles across the country.
Triggering rainfall might also be important to meeting our energy needs moving forward. The utility company Idaho Power has a cloud seeding program that’s meant to keep its hydroelectric plants running. That program began in 2003, and the company claims it produced nearly half a million acre-feet of additional water in the region in 2020.
Studies have shown cloud seeding may increase precipitation by anywhere from 5 to 15 percent. Friedrich cautions, however, that this can vary wildly, and we still don’t have a great sense of what interfering with condensation and precipitation in the atmosphere will actually lead to.
“Once you manipulate the cloud, you don’t really know what this cloud would have produced in terms of precipitation without the manipulation,” Friedrich said. “It’s really important to run models where you can maybe simulate the impact of these different technologies.”
There are plenty of books and films that suggest our attempts to control the weather will simply backfire and usher in a global apocalyptic nightmare—the sky’s gone black, the crops are dead, and humanity is fighting with each other to stay alive.
But cloud seeding isn’t as extreme or new as a lot of other ambitious geo-engineering proposals, and that means scientists have a better understanding of how it works. Cloud seeding was actually first attempted by an American chemist and meteorologist named Vincent J. Schaefer in 1946. He flew a plane over Massachusetts and released pellets of dry ice into clouds, and he was able to help produce snow.
"Since ancient times man has dreamed of manipulating the weather to his advantage," Schaefer wrote in 1968. "His efforts to this end have ranged from drawing pictographs, lighting ceremonial fires, participating in rain dances and then during the past twenty-one years in directing his attention toward utilizing certain scientific relationships to initiate physical and chemical reactions in the atmosphere." Seemingly overnight, Schaefer had accomplished what was once impossible for millennia.
The science behind cloud seeding is deceptively simple. Rain occurs when too much water vapor in the air condenses. Clouds become too heavy to stay together, and the water falls back to the ground as liquid droplets. Water vapor condenses around minuscule particles in the air, so cloud seeding involves introducing more particles into clouds to induce more precipitation.
A newer idea for cloud seeding—first proposed by researchers at the University of Reading in 2017—involves actually electrifying water droplets in clouds. A positive or negative charge can merge with other droplets, and heavier droplets are more likely to fall. The UAE has been pioneering this technique with its own cloud seeding projects, and the country’s own meteorology program claims it is working.
All of these programs are being taken more seriously thanks to the fact that the science and technology behind cloud seeding is growing more sophisticated every year. Armin Sorooshian, a chemical and environmental engineering professor at the University of Arizona, told The Daily Beast that big data and machine learning are being used to better understand how to make clouds produce rain. Having a better sense of the sizes of particles and droplets distributed in the air and how they influence cloud formation could give scientists more hints into how to cater cloud seeding to meet specific goals.
This kind of research can also help scientists better understand climate change, Sorooshian said. There’s still a lot we don’t know about how particulate matter created by human activity affects clouds.
“I’m currently leading this huge NASA mission called ACTIVATE, and the whole point of this $30 million project is just to understand the science of aerosol-cloud interactions, because it is thought to be the largest uncertainty in our understanding of how the climate is changing,” Sorooshian said. “It has to do with these interactions between particles and clouds.”
There are, of course, risks involved with manipulating the weather—the books and films that envision these calamities have a point. We should be careful about how much cloud seeding we do, Sorooshian said. If you’re deploying a compound like silver iodide into the air, there’s a concern it could fall from the sky and alter a body of water’s pH levels, for example, which could impact the health and stability of the plants and animals below.
“I’m not entirely sure if I would advocate for people to start doing this aggressively right now,” Sorooshian said. “We need to learn more.”
As droughts become more common due to climate change, cloud seeding is poised to become a more regularly used tool to help alleviate water shortages. But it should be thought of as one tool within an arsenal of solutions. If there are no clouds in the sky, cloud seeding will lead to bupkis. Groups making huge bets on cloud seeding, like the Chinese government, would do well to keep this in mind.
“If you’re thinking about mitigating drought, then you need to have a bigger plan,” Friedrich said. “Not just cloud seeding.”