On Tuesday, I shared an article about condensation trails, commonly called contrails and explained the science behind how they form. If you missed it, you can read it here.
I expected a few comments about so-called “chemtrails” or “chemical trails,” but I was surprised by the intensity and emotion behind some of the responses. Despite producing hundreds of weather explainer videos over the years, this was the first time I had been called a “media shill” or a liar.
What surprised me even more, though it probably shouldn’t have, was the widespread confusion between contrails and cloud seeding. These are completely different things. I also received a number of comments referencing geoengineering, which again is not the same thing.
Today, I want to explain the differences between contrails, cloud seeding, and geoengineering, what they are, how they work, and why they are often misunderstood. Below are the three different types of contrails.
Cloud seeding is a real, well-studied practice:
It works by dispersing small amounts of silver iodide, into suitable clouds using aircraft. The goal is to enhance precipitation by encouraging ice crystal formation within clouds that already contain enough moisture to produce rain or snow.
Cloud seeding does not create clouds or precipitation from clear skies. It can only be effective when clouds with the right structure and moisture are already present. For that reason, cloud-seeding aircraft operate within or near existing storm systems, not in dry, cloud-free air.
I searched extensively for examples of cloud-seeding aircraft producing trails that resemble high-altitude contrails and could not find any. The primary reason is that cloud-seeding planes fly much lower than commercial jets. And releasing seeding material in clear skies would be ineffective and pointless.
The first scientific cloud-seeding experiments were conducted in 1946 by American meteorologist Vincent J. Schaefer, who introduced dry ice into a supercooled cloud. Snow was observed shortly afterward, leading to additional experiments and expanded research over the following decades.
Today, peer-reviewed research indicates that cloud seeding can increase precipitation by approximately 5% to 15% under the right conditions. It is important to note that cloud seeding does not create clouds or generate precipitation from dry air. It only works when clouds already contain sufficient moisture and the appropriate atmospheric structure to produce rain or snow.
When those conditions are present, cloud seeding can enhance precipitation and has been used as a water-management tool in drought-prone or water-scarce regions. I have personally seen cloud-seeding operations used in both California and Texas.
One of the most frequently cited—and misunderstood—chapters in cloud-seeding history is Operation Popeye during the Vietnam War. From 1967 to 1972, the U.S. government seeded clouds over parts of Southeast Asia in an attempt to extend the monsoon season, muddy roads, and disrupt supply routes along the Ho Chi Minh Trail.
The limitation was the science itself. As recent studies show, cloud seeding typically increases precipitation by about 5% to 15% under favorable conditions. In practical terms, if a storm was expected to produce 5 inches of rain, cloud seeding might add less than an inch. That modest increase fell far short of producing the large-scale impacts the operation hoped to achieve. As a result, Operation Popeye was eventually discontinued.
During this era, weather modification captured the imagination of policymakers. A quote by then Vice President Lyndon B. Johnson reflects that mindset: “He who controls the weather will control the world.” In reality, Operation Popeye demonstrated just how limited human influence over weather truly is.
There were also attempts to modify hurricanes. Beginning in 1962, the U.S. government launched Project Stormfury, a series of experiments aimed at weakening tropical cyclones by seeding them. Hurricanes Esther (1961), Beulah (1963), Debbie (1969), and Ginger (1971) were among those seeded.
After years of field experiments, laboratory research, and modeling, NOAA scientists concluded that hurricanes could not be controlled or meaningfully altered through cloud seeding. Project Stormfury was officially terminated in 1983.
Subsequent research has only reinforced that conclusion. As MIT scientist Moshe Alamaro has noted, a single powerful hurricane releases energy comparable to the combined output of all the world’s power plants, far beyond anything humans can influence.
Here’s the bottom line on cloud seeding:
- When it is conducted, it looks nothing like high-altitude contrails.
- While the benefits can be meaningful for farmers, ranchers, and ski resorts, the overall impact is small in the context of large-scale weather systems.
- Cloud seeding cannot create storms, steer weather, cause floods, or generate droughts.
Geoengineering:
I want to be honest and clear here. I am a Certified Broadcast Meteorologist. My expertise is in weather and climate, not geoengineering. As I read through many of the geoengineering related comments, it became clear that this topic sits outside my primary area of specialization. That said, I can offer some general, well-established context.
I also recognize that for some people who firmly believe the government is intentionally harming the public through geoengineering, nothing I say will change their minds. Still, facts and definitions matter, and that’s where I’ll focus.
What is Geoengineering?
By definition, geoengineering, also known as climate engineering or climate intervention, refers to deliberate, large-scale efforts to alter Earth’s climate system, primarily in response to human-caused climate change.
Broadly, geoengineering concepts fall into two categories:
- Carbon Dioxide Removal (CDR) These approaches aim to remove carbon dioxide from the atmosphere.
- Solar Radiation Management (SRM) These ideas focus on cooling the planet by reflecting a small portion of incoming sunlight into space.
Both are theoretical or experimental approaches intended to address global climate change not weather on a local or day-to-day scale.
Is Geoengineering being used today?
Not at any large or operational scale.
Most geoengineering work today is limited to:
- Computer modeling
- Laboratory research
- Small, tightly controlled experiments
In the United States, many proposed outdoor experiments have been delayed, canceled, or restricted due to public concern, environmental risk, and ethical questions surrounding intentional climate manipulation. These concerns are taken seriously within the scientific community.
One challenge today is the lack of a comprehensive global governance framework. There is no international rulebook that clearly defines who could deploy geoengineering, how it would be regulated, or how unintended consequences would be handled. That uncertainty is one of the major reasons widespread deployment has not occurred.
Bottom line:
Focusing strictly on the discussion sparked by my earlier article:
- Geoengineering does not look like the contrails shown in my photos.
- Geoengineering is not cloud seeding.
- Geoengineering is not a covert program designed to make people sick.
As I said earlier, geoengineering is not my area of expertise. If you have credible, peer-reviewed, scientifically supported evidence that shows otherwise, I want to see it.
But I’ll repeat what I said on Tuesday: Extraordinary claims require extraordinary evidence. Most of the comments I received earlier this week were completely emotion-based arguments.
Seeing lines in the sky one day and feeling under the weather the next does not mean the government, or any other entity, is targeting you. Weather, aviation, and human health are complex systems, and coincidence is not causation.
Clear science matters. That’s what I’ll continue to focus on.