Is Cloud Seeding Good, Bad, Or Ugly?

Is Cloud Seeding Good, Bad, Or Ugly?

The Chinese Communist Party celebrated its centenary on the 1st of July, 2021. For such a celebration, clear skies and clean air would be ideal. For the capable nation-state, however, one needn’t hope against the whims of the weather. One can simply control it instead!

A recent paper released by Tsinghua University indicated that China had used cloud seeding in order to help create nicer conditions for its 100-year celebration. Weather modification techniques have been the source of some controversy, so let’s explore how they work and precisely what it was that China pulled off.

What Is Cloud Seeding?

The basic principle of cloud seeding, using chemicals as nucleation points for precipitation in clouds. Credit: Naomi E Tesla, CC-BA-SA-4.0

Cloud seeding is a relatively simple process that aims to induce or vary the amount of precipitation that falls from the sky. Various substances can be dispersed into cloud formations, serving as nuclei for ice crystals or water droplets to form. Once reaching a certain size and weight, these then fall to the ground as rain or snow or other forms of precipitation.

A significant variety of methods exist, with silver iodide being a popular choice. This is as the substance bears a similar crystal structure to that of water ice, allowing it to serve as a nucleation point for condensation, helping to form snowflakes in clouds. The material can be delivered directly via aircraft or rockets, or released into updraft airstreams from generators on the ground.  Actual amounts of chemical used are quite small, with minimal polluting impact.

The technique is useful, as it allows some level of control over precipitation. It can, in theory, be used to cause clouds to rain over an area, to either make an area wetter when desired, or to remove water from the atmosphere so that later days will be drier. Cloud seeding does rely on the presence of moisture already in the cloud system, however; it cannot cause precipitation where no atmospheric water exists.

China’s Applications

As reported by the South China Morning Post, the recent research document indicated evidence that cloud seeding had been used in the days leading up to the centenary celebrations. In the lead up, local air pollution levels were high, despite reported efforts by Chinese officials to close heavily-polluting factories ahead of time. Low winds in the area were cited as a possible complicating factor that was preventing the pollution from clearing.

Researchers claimed that a cloud-seeding operation had occurred for two hours on the day prior to the ceremony, with reports of rockets being fired into the sky from residents in the area. The paper asserts that the rockets spread silver iodide particles into the clouds to create rainfall ahead of the event.

The paper also indicated an improvement in PM 2.5 particulate levels, significantly improving the air quality readings from “moderate” to “good” in the affected area. The paper notes that they found little evidence of anything other than artificial rainfall that would be responsable for the better air. Easily-accessible online data from the area is difficult to compare, as the results are averaged over a full 24 hours. However, a small drop is noted from June 29 through to July 1.

Often referred to as “blueskying,” the weather modification method has been used in similar ways before, such as during the 2008 Beijing Olympics. In fact, China’s history with cloud seeding goes all the way back to early efforts in 1958 to help bring rains to agricultural areas in the north of the country.

Since then, China has invested heavily, with the country’s weather modification organizations reportedly employing over 35,000 people, including everyone from meteorologists to simple farmers, charged with firing shells into the atmosphere bearing silver iodide or other seeding agents.

So What’s The Problem?

A Royal Malaysian Air Force plane loads up with water and sodium chloride for cloud seeding, hoping to generate rain to combat smog from forest fires. Credit: Getty Images

There are plenty of benefits to getting rain on command – water for crops, rain to help remove particulate pollution from the air, or even just keeping rivers flowing in periods of drought. However, the practice of cloud seeding has drawn some controversy, due to the potential for either deliberate or unintended negative outcomes.

China has already put forth bold plans, and hopes to one day divert water vapor in the skies above the Yangtze River Basin to fill the drier Yellow River basin in the country’s north. The hope is to shift up to 5 billion cubic meters of water annually to where it’s needed.

However, projects on such a large scale could easily effect water that would typically fall in other regions. Fears are that south-east Asia and India could be affected, if rain is directed to fall where it suits China best instead. Outlets like the Times of India openly speculate that this could have serious affects on India’s rainfall, and thus its vital water supply.

Cloud seeding already has a history of being used with less-than-pure intentions in the past. United States forces infamously implemented Operation Popeye during the Vietnam War, a cloud-seeding operation with direct military goals. The project hoped to maintain rainfall on the strategically-vital Ho Chi Minh Trail, such that the dirt roads would turn to mud and break the Vietcong’s supply lines. The project began in 1967 and lasted until 1972, with pilots seeding clouds with silver or lead iodide from canisters spewing chemical-laden smoke into the air.

Cloud seeding equipment as fitted to a Piper Cheyenne II light aircraft. Credit: Getty Images

The results were mixed, and secrecy around the project means that it’s hard to determine exactly what Operation Popeye achieved. However, after it was revealed to the public in the 1970s, it quickly led to the establishment of the Environmental Modification Convention, which aimed to ban the use of weather modification for military aims.

It’s also been cited that cloud seeding may have been used in the wake of the Chernobyl disaster, aiming to cause rain to help remove nuclear fallout from the atmosphere before the radioactive cloud reached Moscow itself. The assertion has repeatedly been denied by authorities, but it’s another example of how weather and rainfall could be manipulated for better or for worse.

Meanwhile, small and large cloud seeding projects go on around the world on a regular basis. Some are for research, others hope to break droughts, and some even want to fight fires.

A Controversial Technology

Like many technologies, cloud seeding is as controversial as the way in which it is used. The problem, however, is that the results of cloud seeding are so diffuse and difficult to quantify that it can be hard to police or even accurately measure its effects.

It’s entirely possible to fire a bunch of chemicals into a cloud, and measure how much rain falls in the immediate aftermath. The cloud may have rained anyway, and controlling for this effect is difficult because cloud seeding relies on the humidity being in the air in the first place. The downstream effects are similarly murky. A country may run some experiments or programs to seed clouds in their own territory, but proving that this causes a drought 1,000 miles away would be incredibly difficult.

Regardless, humans have always wished to control the world around them, and weather modification is just another way to do just that. With any technology, expect to see it used and misused in equal measure going forward. Only when we truly understand the effects, can we make sure that we see more of the former, and less of the latter.