Contrails – the white lines in the sky created by planes – can double the amount of warming caused by aviation’s carbon emissions
Experts have claimed that the climate-damaging vapour trails from jet planes could be eliminated for just a few pounds per flight.
Researchers suggest that contrails — the white lines in the sky created by planes — can double the amount of warming caused by aviation’s carbon emissions.
However, a study by the Transport & Environment advocacy group found that adjusting the flight paths of very few flights could reduce global contrail warming by more than half before 2040. This could involve just three per cent of flights, which, according to the analysis, generate about 80 per cent 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.
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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 five per cent or less but 80 per cent 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.”
According to the study, factors such as geography, seasonality, time of day, and flight latitude significantly influence whether a contrail is warming. In 2019, flights over North America, Europe, and the North Atlantic region accounted for more than half of global contrail warming.
Evening and night flights, as well as those in winter, have the largest warming contribution. The research revealed that the climate benefits of contrail avoidance could be 15 to 40 times greater than the CO2 penalty from a re-routed flight. These benefits are expected to increase as technology advances. Contrail avoidance is a solution that could be widely implemented within the next decade, provided decisive action is taken, according to Transport & Environment.
A campaign group has urged that from 2027, all flights taking off or landing in the European Union should have their contrails tracked, pushing regulators to prep Europe’s skies for incorporating contrail avoidance. They’ve also called for focus on funding research into dodging these trails and proposed rewards for airlines and makers who get ahead of the game.
“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. However, he warned, this doesn’t make cutting aviation’s carbon footprint any less critical, insisting: “Policymakers and the industry cannot afford to lose the climate opportunity of this decade.”
The group cautioned that despite the potential benefits of avoiding contrails, the challenge of tackling the sector’s carbon emissions remains a top priority.
When it comes to how much global warming is caused by aviation, Effective Radiative Forcing is the important thing. That is a measure of the extra energy (heat) trapped by the atmosphere. It is a way of comparing the physical impact of different climate problems, like contrails and CO2.
One study found that CO2 emisisons from planes was responsible for 34 per cent of their Effective Radiative Forcing, contrails 57% and others (notably nitrogen oxides) 9%.
“Newer studies have estimated other values for contrail warming, usually lower, but still of similar magnitude to CO2 warming. In any case, the gist is: contrails are a significant climate issue, similar to aviation’s CO2 emissions, and there are effective, low cost solutions that could solve this in the coming decade,” Carlos told the Mirror.