Solar Radiation Modification (SRM) Primer

Distinguishing SRM from Chemtrails, Contrails, and Weather Modification

Authors

Mitch Poulin

SRM is sometimes conflated with contrails, chemtrails, and weather modification, but the three are distinct concepts.

SRM comprises a series of proposed technologies that, if implemented, would aim to cool Earth by reflecting sunlight away from the planet.

Contrails (condensation trails) are long white clouds that are sometimes visible behind airplanes. They are composed of aircraft exhaust and water vapor and are an aviation byproduct that is not designed or intended to cool the planet.13 Contrails both reflect solar radiation into space and trap some of Earth’s heat in the atmosphere.14 By trapping more radiation than they reflect, contrails have a small net warming effect.15

Conspiracy theorists define chemtrails (chemical trails) as contrails that have been intentionally modified to disperse toxic chemicals for population control, mind manipulation, and/or to change weather patterns.16 This theory is not supported by evidence. However, well-known figures like U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. have echoed the theory, and he is not alone; a 2017 study found that at least 10 percent of Americans believe the theory is completely true.17 The U.S. Environmental Protection Agency (EPA) website states that, though some chemicals are intentionally sprayed from airplanes to combat fires or promote crop growth, the federal government is unaware of any chemicals being released from aircraft for weather control or other nefarious purposes.18

Weather modification is the act of intentionally changing localized weather patterns, usually to increase precipitation, while SRM is intended to deflect solar radiation (in the case of MCB and SAI) or facilitate atmospheric heat release (in the case of cirrus cloud thinning) to cool the planet.

Endnotes

13
“Contrails,” NASA.
14
“Are Chemtrails Harmful to the Environment?” National Academies of Sciences, Engineering, and Medicine, August 22, 2025.
15
Roger Teoh, Zebediah Engberg, Ulrich Schumann, et al., “Global Aviation Contrail Climate Effects from 2019 to 2021,” Atmospheric Chemistry and Physics 24 (10) (May 2024): 6071–6093; and Andrew Gettelman, Chieh-Chieh Chen, and Charles G. Bardeen, “The Climate Impact of COVID-19-Induced Contrail Changes,” Atmospheric Chemistry and Physics 21 (12) (June 2021): 9405–9416.
16
Holly Jean Buck, “Understanding and Addressing ‘Chemtrails,’” Salata Institute for Climate and Sustainability, Harvard University, June 25, 2025.
17
Madison Czopek, “RFK Jr. Says DARPA Is Spraying Chemtrails—With No Evidence and No Basis in Fact,” Poynter, May 7, 2025; and Dustin Tingley and Gernot Wagner, “Solar Geoengineering and the Chemtrails Conspiracy on Social Media,” Palgrave Communications 3 (1) (October 2017): 12.
18
U.S. Environmental Protection Agency, Office of Air and Radiation, “Information on Contrails from Aircraft,” October 6, 2016.