Five years ago, China was the most trigger-happy cloud seeder in the world. It was creating 55 billion tons of artificial rain a year, with plans to quintuple that amount. In 2013, launching cloud-seeding chemicals by rocket into the sky or spraying them from planes were the preferred methods.
Now, reportedly equipped with new military weather-altering technology, China is embarking on its biggest rain-making project yet, the South China Morning Post says. Using a system developed by the state-owned China Aerospace Science and Technology Corporation, the Hong Kong news outlet reports, the country plans to build tens of thousands of combustion chambers on steep Tibetan mountainsides. The chambers would burn a solid fuel, which would result in a spray of silver iodide billowing towards the sky.
The particles, much like those already sprayed from planes, would provide something for passing water vapor to condense around, forming clouds. And the clouds would bring the rain.
A single cloud-seeding chamber could create a strip of clouds covering a five-kilometer area, the Morning Post states.
Water in Tibet is good for Asia
The Tibetan plateau was chosen for its massive impact on water supply. Climate models predict it will see severe drought as temperatures rise and regional rainfall decreases. This poses a major problem that extends far beyond Tibet itself; the Tibetan plateau is vital to the water supply for much of China and a large swath of Asia. Its glaciers and reservoirs feed the Yellow, Yangtze, Mekong, and other major rivers that flow through China, India, Nepal, and other countries.
The chambers were said to have first been developed as part of a Chinese military program to use weather modification for defense purposes. They “burn fuel as cleanly and efficiently as rocket engines, according to the Morning Post, “releasing only vapours and carbon dioxide, which makes them suitable for use even in environmentally protected areas.”
The plan, announced this month, would be the world’s largest cloud-seeding project. It is intended to force rainfall and snow over 1.6 million square kilometres (620,000 square miles)—an area roughly three times the size of Spain (if you’re in Australia, then it’s the size of Queensland).
“More than 500 burners have been deployed on alpine slopes in Tibet, Xinjiang and other areas for experimental use. The data we have collected show very promising results,” an unnamed researcher told the Morning Post. “Sometimes snow would start falling almost immediately after we ignited the chamber. It was like standing on the stage of a magic show.”
Is this a good idea?
Plenty of questions remain about the safety and efficacy of such a system. First of all, releasing silver iodide at the ground level could affect humans like small particles in dust or smoke do. “Based on their small size they can be inhaled deeply into the lungs, potentially causing health issues for the workers operating the equipment and others in the area,” explains Faye McNeill, a chemical engineer at Columbia University who studies atmospheric aerosols. “In other words, these particles will add to the amount of fine particulate matter.”
The silver iodide would eventually fall back down to Earth with the rain, but McNeill tells Quartz that isn’t as much of a concern, at least not for people. “Once the silver iodide enters the groundwater, it is not expected to be in a very toxic form, but it may disrupt the aquatic ecosystem.”
There are also ethical implications of sucking moisture out of the air. You’re invariably taking rain away from another region, says Adam Sobel, an atmospheric scientist at Columbia University’s engineering school: “If you’re making it rain where it wouldn’t otherwise, you’re taking water out of the air that would have rained elsewhere.”
Update: A previous version of this article misstated the origin of the water vapor that would fuel the cloud-seeding project and incorrectly stated that if China manages to make a large enough volume of rain fall on Tibet, it could reduce the rain that falls on India.