Chemtrails

The Story

Look up on a clear afternoon near a busy flight path and you will see them: long white lines drawn across the sky by jets. Sometimes they vanish almost at once. Sometimes they linger for hours and spread into a haze. To scientists they are contrails, short for condensation trails. To a lot of people they are something else.

The chemtrail theory holds that the lingering lines are chemicals deliberately sprayed from aircraft. A 2016 study of the theory found that its claimed purpose has shifted. At first it was most often said to be 'control over population, food supply, and/or the weather.' After climate geoengineering research emerged in the 2000s, the theory increasingly said the spraying was meant to alter the climate. A survey cited in the study found that 2.6 percent of respondents in an international poll thought a secret spraying program was 'completely true,' and 14 percent 'partly true.'

Of 77 atmospheric experts surveyed, 76 'said they had not encountered evidence' of a secret spraying program.

Governments say the explanation is ordinary physics. The UK Department for Transport says contrails 'form when the warm moist exhaust fumes from an aircraft mixes with the cold ambient air producing ice crystal clouds,' and that they 'are essentially ice.' Why do some last and others not? 'If the air around the plane is very dry, the ice crystals will turn back into water vapour and disappear within a few minutes,' it says, while 'humid air causes the ice crystals to remain and may even spread out.' A flight level 1,000 feet higher or lower can be enough for one plane to leave a trail and another not. And the grids? Aircraft 'often follow similar routes separated by altitude, time, lateral distance and direction.'

Believers also collect samples of water, soil and snow and test them for aluminum, barium and strontium. The UK government answers: 'We have no credible evidence of the release of chemtrails,' adding that aluminosilicates 'are common in clay soils and a wide range of other minerals.'

In 2016, researchers at the University of California, Irvine, and the Carnegie Institution for Science put the claims directly to experts, atmospheric chemists who study contrails and geochemists who study dust and pollution. They showed them the photos and lab results that chemtrail websites cite. '76 of the 77 scientists (98.7%) that took part in this study said they had not encountered evidence' of a secret program. The one exception cited 'high levels of atm[ospheric] barium in a remote area with standard 'low' soil barium.' For the lab results, experts repeatedly said the numbers looked like ordinary soil or dust. One described the recommended home sampling method, a glass jar with a metal lid, as one that 'will contaminate the sample.'

Part of what keeps the theory alive is that real cousins of it exist. Cloud seeding, spraying particles such as 'dry ice or silver iodide, onto clouds in order to increase precipitation,' has been used openly by some states and countries. Scientists have proposed injecting reflective aerosols into the stratosphere to cool the planet; the UK government says 'we do not use SRM or have plans to do so.'

Contrails do matter, just not in the way the theory says. The UK government notes that persistent contrail cirrus 'can affect the reflection of solar radiation and therefore have an impact on the Earth's climate,' a real effect scientists are still working to measure.