Science, Tech, Math › Science Chemtrails Versus Contrails Exploring the Chemtrail Conspiracy Theory Share Flipboard Email Print Persistent criss-cross contrails occur over highly trafficked areas with high humidity. Richard Newstead/Getty Images Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 04, 2019 Do you know the difference between a chemtrail and a contrail? A contrail is an abbreviation for "condensation trail," which is a visible white vapor trail produced as water vapor condenses from aircraft engine exhaust. Contrails consist of water vapor or tiny ice crystals. The length of time they persist varies from several seconds to a few hours, depending largely on the temperature and humidity. Chemtrails, on the other hand, are "chemical trails" purportedly resulting from an intentional high-altitude release of chemical or biological agents. While you might think chemtrails would include crop dusting, cloud seeding and chemical drops for firefighting, the term is only applied to illicit activities as part of a conspiracy theory. Proponents of the chemtrail theory believe chemtrails may be distinguished from contrails by color, displaying a criss-cross trail pattern and persistent appearance. The purpose of chemtrails might be weather control, solar radiation control, or testing of various agents on people, flora or fauna. Atmospheric experts and government agencies say there is no basis for the chemtrail conspiracy theory. Key Takeaways: Contrails vs Chemtrails Contrails are condensation trails left in the sky when the water in aircraft engine exhaust condenses to form artificial clouds.Contrails may last a matter or seconds or persist several hours. Contrails dissipate more slowly when a lot of water vapor is present in the atmosphere. Lower temperatures also aid contrail persistence.Chemtrails refer to a conspiracy theory. The theory stems from a belief in intentional high-altitude releases of chemicals or biological agents.Supposedly, chemtrails are indicated by contrails that persist, occur in a criss-cross pattern, or display colors besides white.Scientists and government agencies have found no evidence supporting the existence of chemtrails. It is true agents are released into the atmosphere from time to time for cloud seeding and experiments on controlling solar radiation. Are Contrails Harmful? Even if it's assumed contrails serve no nefarious purpose, it's worth asking whether they impact the environment and whether they are potentially harmful. To answer this question, it's useful to understand how contrails form. An aircraft with a jet engine burns fuel and releases an exhaust plume into the atmosphere. The composition of the fuel is tightly regulated to minimize impurities, but may contain a small fraction of nitrogen or sulfur. Combustion releases carbon dioxide and water, two important greenhouse gases. Sulfur particles provide nuclei on which water vapor may condense into droplets. The collection of droplets appears as a contrail. Basically, a contrail is an artificial cloud. Criss-crossing contails occur in high traffic areas. Researchers know the "clouds" produced by aircraft have an impact on air temperature and may impact rainfall and weather patterns. Basically, contrails have the potential to affect global climate change. However, the nature and extent of the change is uncertain. Contrail cover is expected to change over time as aircraft technology, the number of aircraft, and humidity conditions evolve. Persistent contrail cloud cover is expected to increase, at least until 2050 (the end date of the forecast). Aircraft emissions are regulated because they have the potential to contribute to ozone formation and smog. Jet engines emit nitrogen oxides, carbon monoxides, carbon black, and hydrocarbons (as well aforementioned carbon dioxide, water, and sulfur). However, contrails are not believed to have any immediate effect on public health. Small aircraft do use leaded fuel and release lead into the atmosphere (but don't produce visible trails). Modern "Chemtrails" If the concept of chemtrails is expanded to include the intentional release of chemicals into the atmosphere (not for some evil purpose), then such projects do exist. Weather modification in the form of cloud seeding is used in parts of the world, including China and Southeast Asia. Some of the chemicals used in the process (typically silver iodide, potassium iodide, table salt, liquid propane, or dry ice) can affect human health and damage the environment. Solar radiation management is an area of ongoing study intended to reflect sunlight and reduce global warming. Some proposed methods include the release of sulfate aerosols and other chemicals into the air. While toxicity is not a primary concern, altering the weather patterns will definitely have environmental effects. Sources Cama, Timothy (March 13, 2015). "EPA confronts 'chemtrails' conspiracy talk." The Hill.Johnson, M. Kim (December 1999). "Chemtrails Analysis." NMSR Reports, 5(12).Radford, Benjamin (2009). "Curious Contrails: Death From the Sky?" Skeptical Inquirer.Smith, Oliver (July 4, 2017). "Incredible contrail made by Boeing 787 - what causes them, and are they part of a global conspiracy?" The Telegraph.US Environmental Protection Agency (September 2000). Aircraft Contrails Factsheet.