Jet fuel is harmful to the environment. Contrails are even worse.

Every time an airplane flies, it emits a trail of pollutants into the atmosphere. They don’t know how the industry behind them can fix it.

Since long, the fact that planes are climate-damaging fuelhogsaviation accounts to two per cent of human-caused global warming has been apparent to the public. However, it is becoming increasingly obvious that more jet fuel may be required to address the larger contributor to the warming climate: contrails. Researchers are quickly gaining insight into how these anthropogenic cloud formations contribute to global warming and how they can be prevented.

MORE: Why these artists leave ghostly sculptures at bottom of ocean

The planes continuously emit a trail containing substances such as carbon dioxide, water vapour, and black carbon (soot). When aircraft fly through cold, humid air, water vapour and large soot particles combine to form a long stream ice particles. Sebastian Eastham, a research scientist at MITs Laboratory for Aviation and the Environment, says that the ones that disappear quickly don’t pose a problem. However, cirrus clouds can persist for hours and trap large amounts of thermal radiation that would otherwise escape to space. Contrails are a sudden, large contribution to global warming. They have the effect of retaining a significant amount more energy in the Earth’s atmosphere. Carbon dioxide, however, has a more sustained, but less acute, energy-trapping effect.

The challenge of aviation is therefore avoiding the cool, humid areas that are ripe to create contrails. It is difficult to predict their locations, which can vary from hour to hour. This is a problem for air traffic control and modelling. The theory is that temporarily flying higher or lower for short stretches of certain flights can result in huge savings in contrails. However, this comes at the expense of relatively little extra fuel burn and carbon emissionemitting a little more to save the earth. At a conference last May, John Green of the Royal Aeronautical Societys stated that this is the best way to reduce aviation’s climate impact. The industry is now turning simulations into real-world examples. United Arab Emirates Etihad Airways teamed up with a U.K flight analysis firm to adjust the route of a Boeing 787 flying from Heathrow to Abu Dhabi. It claims it avoided the equivalent of 64 tonnes CO emissions by emitting only 0.48 tonnes more.

READ:Politics is the problem in energy and climate

Alternative fuels are another option for avoiding contrails. The National Research Council of Canada has tried out jets using crop-based biofuels. They are less carbon intensive over their lifetime than jet fossil fuels. Anthony Brown, NRC research pilot engineering, says that they do not produce lower inflight carbon emissions than jet fuels. However, they significantly reduce the amount of soot particles that contribute to the formation of contrails. Brown says that because it is impossible to predict when contrail-prone flights will occur, switching fuels is a better way to address this problem than changing flight paths.

However, it will take many years before either solution is available for industry-wide use. While conspiracy skeptics still fear chemtrails, there are reasons to look up and see lingering jet exhaust clouds, and be a little anxious.

This article appears in print within the March 2022 issue. Macleans Magazine with the headline Menace in the Mist. Subscribe to the monthly print magazine Here.