The climate-damaging vapour trails from jet planes could be eliminated for just a few pounds per flight, according to experts. Researchers say contrails – the white lines in the sky created by planes – can double the amount of warming caused by aviation’s carbon emissions.
But tweaking the flight paths of very few flights could reduce global contrail warming by more than half before 2040, a study by the Transport & Environment advocacy group found. This could be just 3% of flights, which, according to the analysis, generate about 80% of the warming associated with contrails.
The simple change is set to be explored for the first time at an event during the Cop29 UN climate conference taking place in Baku, Azerbaijan. Contrails are made up of ice crystals, which form when water vapour condenses on unburned fuel fragments in a plane’s exhaust stream as it travels through cold humid air.
Transport & Environment researchers said changing flight paths to avoid areas where contrails could form will only be needed on a small number of flights for a short part of the journey, at a cost of less than £3.50 per ticket each flight. The analysis showed the extra fuel burned to avoid contrails would be 5% or less but 80% of the warming from its contrails would be eliminated.
The climate benefits from avoiding most of the contrail warming would always be larger than the climate impact from the extra carbon emissions, it found. Carlos Lopez de la Osa, aviation technical manager at Transport & Environment, said: “The aviation industry is being offered a simple and cheap way to reduce its climate impact.
“Some industry actors overstate the scientific uncertainty of warming contrails, but the climate benefits of contrail avoidance are huge and solutions are improving by the day. By identifying the very few flights which cause warming contrails and tweaking their flight paths, we can have an immediate effect on contrails warming. So, let’s no longer discuss whether we have to do it, but how to do it.”
Geography, seasonality, time of day and flight latitude have a strong influence on whether a contrail is warming. Flights over North America, Europe and the North Atlantic region accounted for more than half of global contrail warming in 2019, the study said, while contrails formed by evening and night flights, or in winter, have the largest warming contribution.
The research found that climate benefits from contrail avoidance could be 15 to 40 times larger than the CO2 penalty from a re-routed flight – benefits the researchers say could go up as technology advances. Contrail avoidance is a solution that could be widely implemented in the next decade, providing decisive action is taken, Transport & Environment said.
For this to happen, the campaign group recommended contrails are monitored on all flights departing and arriving to the European Union from 2027 and advised regulators to prepare the European airspace for inclusion of contrail avoidance. It also recommended that funding is prioritised for avoidance research and incentives are offered to early mover airlines and manufacturers.
“There are very few climate solutions that can be implemented so quickly, at so little cost and with little impact to industry and consumers,” Mr Lopez de la Osa said.
“Policymakers and the industry cannot afford to lose the climate opportunity of this decade.”
While the impacts of contrail avoidance could be significant, the campaign group warned that reducing aviation’s carbon emissions would not be any less urgent.