Editor's note: This article is a reprint. Originally published August 8, 2017.
Artificially manipulating the weather is called weather manipulation, and although it sounds like something out of science fiction, more than 50 countries around the world are already engaging in one type of weather manipulation called cloud seeding.One The U.S. Government Accountability Office predicts that 40 U.S. states will experience partial drought-related water shortages within the next 10 years.2
The prospect of using cloud seeding to increase rainfall is the most popular use case, and while it is appealing, it is also quite controversial. In the United States, about $15 million is spent annually on cloud seeding projects, a pittance compared to the $100 million spent annually in China. Nevertheless, cloud seeding in the United States has increased by a third over the past decade.three
For example, in North Dakota, it is not only used to promote rain, but also to suppress hail (and thus reduce hail damage to crops). Cloud seeding is also sometimes used to clear fog.
Meanwhile, in California, “cloud seeders” have been installed on mountaintops to increase rain and snowfall in an effort to combat drought. But as the practice has grown in popularity, some have questioned whether it is cost-effective and whether it could have negative effects on the weather. The latter is why some farmers in North Dakota are calling for an end to the state’s cloud seeding program.
How does cloud seeding work?
Cloud seeding can operate in a number of different ways, but typically involves applying dry ice (icy carbon dioxide) pellets or silver iodide to specific clouds to modify the output. Seeding agents can be applied to the cloud from the ground, but in most cases aircraft are used to apply materials to the cloud.
This occurs by releasing seeding material below the cloud into the updraft or by dropping the seeds directly into the upper region of the cloud. According to the North Dakota Cloud Modification Project (NDCMP):4
“In North Dakota, all seeding is done by aircraft. Base seeding aircraft use a combination of wing-mounted ice core generators and in-situ combustion flares to release seeding material into the updraft below the developing storm. Above the clouds. “The seeding aircraft releases possible flares and dry ice directly into the supercooled cloud.”
There are some considerations regarding which method to use. Direct injections work faster and results are almost immediate. However, the NDCMP points out that this costs more because it requires high-performance aircraft that can fly directly within the cloud at higher altitudes. Updraft treatment performed on a cloud basis is an easier and less expensive method, but results can take up to 30 minutes.
In North Dakota, the program is run under the direction of a radar meteorologist who is responsible for determining when to seed clouds. According to the NDCMP, “in addition to weather conditions, a number of factors, including safety standards, radar information, pilot observations, and aircraft instrument data, influence the decision-making process.”5
North Dakota reports up to 10% increase in precipitation due to cloud seeding
Determining whether cloud seeding is effective is difficult. One reason for this is that many regions using this technology want to process every cloud available for seeding to reap the most potential benefits. However, in Wyoming, the Wyoming Weather Modification Pilot Program (WWMPP) conducted a random cloud seeding program and found that seeding increased snowfall by 5 to 15 percent under ideal seeding conditions.6
Meanwhile, in North Dakota, the NDCMP reported that cloud seeding has resulted in an additional 5 to 10 percent of annual rainfall in the project area and a 45 percent reduction in crop hail losses. As for cost, it is said that the cost of enhancing rain and suppressing hail is only 16 cents per acre.7
Environmental impacts were also reported to be minimal, with the NDCMP noting that “cloud seeding agents, including silver iodide and dry ice, meet all National Environmental Policy Act (NEPA) regulations and are safe for the environment.” They also note that no harmful environmental effects have been detected from cloud seeding using silver iodide, explaining:8
“Silver concentrations in rainwater from seeded storms are well below the acceptable environmental concentration of 50 micrograms per liter set by the U.S. Public Health Service. Additionally, iodized salt consumed by humans has a much higher iodine concentration than is found in rainwater from seeded clouds. Silver iodide is used in very small amounts because it is a very effective ice nucleus.
Based on the average use of silver iodide each summer in North Dakota, it would take nearly 500 years to spread one gram of silver iodide (1/28th of an ounce) evenly over an area the size of a basketball court!”
North Dakota Farmers Demand Stop Weather Manipulation
Not everyone believes cloud seeding is a win-win proposition. Farmers in Ward County, North Dakota, have asked the county commission to suspend their cloud seeding program for the rest of 2017 due to drought, with some opponents arguing the practice could worsen dry conditions. The commission voted 4-0 to ask the Air Resources Board to suspend operations.
“We're not asking for anything radical here. We're asking you to join the other 47 counties in the state that are not trying to change the weather,” spokesman Roger Neshem told the committee. In The Dickinson Press he noted:9
“I said, ‘What are we getting for spending this money?’ The only thing that’s true in this whole situation is that hail insurance rates in Ward County are higher than in the local counties… I think there are people who think that could have a negative impact on the weather patterns here.”
Did Cloud Seeding Cause the Rapid Urban Flooding of 1972?
June 9, 1972 is a day etched in the memory of many residents of Rapid City, South Dakota. In just six hours, the city received 10 inches of rain, with up to 14 inches overnight. Local streams overflowed and the dam on Canyon Lake failed, causing massive flooding in the city, killing 238 people and injuring 3,000.10
Before the flood, the South Dakota College of Mines and Technology was conducting cloud seeding studies in the area, which some suggested may have been responsible for the catastrophic flooding. But an investigation led by the governor concluded that the seeding project was not the cause. Darin Langerud, director of the North Dakota Air Resources Board, told The Green Sheet Farm Forum:11
“There were those who tried to blame cloud seeding on that incident… After that incident, at the request of the governor, a study was done to look into all the details, and the conclusion was that cloud seeding was not the cause of the 1972 Rapid City flood, but it did have a negative impact on interest in cloud seeding.”
California seeds clouds to fight drought
California is one of the U.S. states that has begun cloud seeding to increase rainfall in drought-stricken areas. In 2002 and 2016, Los Angeles and other municipalities used hilltop “flare trees” to send silver iodide into clouds. The problem is that, as with any other field utilizing technology, its effectiveness depends on getting the conditions right.
“Part of the secret is finding the right geographic and meteorological conditions, as well as placing the silver iodide in the right spot in the cloud,” Scientific American says, “while not creating massive storms or inducing rainfall in places vulnerable to dangerous flooding and landslides.” or other adverse effects.”12
The news outlet also quoted William Cotton, an atmospheric scientist and professor emeritus at Colorado State University, who said cloud seeding could be more of a political move than anything else. “For most water agencies, it’s just about going out and doing something,” he said.
Don Griffith, president of North American Weather Consultants, which has been seeding clouds for more than 50 years, offered another, less than enthusiastic assurance. Asked whether California’s cloud seeding efforts have worked, he told Scientific American, “That’s a very difficult question to answer. We think and hope so, but there’s no way to prove it.”13
In fact, there is a misconception that cloud seeding can end droughts. In practice, this is impossible because droughts are characterized by a lack of precipitation-producing clouds, and these clouds are necessary for cloud seeding opportunities.
So during a drought, there’s little chance of successful cloud seeding. “Nobody can make clouds,” Roelof Bruintjes, an atmospheric scientist at the National Center for Atmospheric Research, told Scientific American.14
There is an attitude that doing something is better than doing nothing, but it remains to be seen whether this will hold true. According to the NDCMP, cloud seeding could also be used to increase precipitation before and after a drought to “mitigate rainfall reductions during drought periods.”15
But it’s not a quick fix that can suddenly make rain fall from the sky during a long drought. “Cloud seeding is more of a long-term water management tool,” Bruintjes said.16
What are the risks and ethical issues of cloud seeding?
Changing the weather is not something to be taken lightly, and cloud seeding is no exception. The technology has been used for over 70 years, including during the Vietnam War, but questions still remain as to whether the practice is beneficial or has unintended consequences. The American Meteorological Society (AMS) has noted that the latter cannot be ruled out.17
“Unintended consequences of cloud seeding, such as changes in precipitation or other environmental impacts on the leeward environment of the target area, have not been clearly demonstrated but cannot be ruled out. Additionally, cloud seeding agents may not always be successfully targeted; , the intended effect in areas other than the desired target area.
This raises ethical concerns that activities undertaken for the benefit of some may have undesirable effects on others. Sometimes unintended effects may cross political boundaries. Climate change programmes should be designed to minimize negative impacts. In some areas, international cooperation may be required,” he said.
Moreover, weather modification does not end with cloud seeding. For example, programs have been attempted to reduce the intensity and/or direction of tornadoes and tropical storms, and other methods besides cloud seeding have been used to increase precipitation. “The effectiveness of these other techniques is much less known, and they are much more difficult to scientifically substantiate, both statistically and physically, than cloud seeding,” AMS said.
To minimize the risks and ethical concerns that arise from inherently unpredictable science, they recommended well-designed and supported research programs that “improve the predictability of unperturbed weather and the magnitude of weather-modifying effects.” In short, following the precautionary principle, we should learn more about the immediate and long-term impacts of climate-modifying technologies before deploying them on Earth.
