In the face of growing public criticism, many airlines are looking for more ways to cut down on their enormous carbon footprint.
But a new paper has ‘thrown a spanner in the works’ for the aviation industry as it reveals that modern aircraft are actually worse for the environment than older models.
Modern planes fly at higher altitudes, creating longer-lasting contrails than older models, according to researchers from Imperial College London.
Just like natural clouds, these contrails trap excess heat in the atmosphere and may contribute more to climate change than the carbon produced by burning jet fuel.
Dr Edward Gryspeerdt, lead author of the study, says: ‘Most people do not appreciate that contrails and jet fuel carbon emissions cause a double-whammy warming of the climate.’
A new study warns that modern planes could be worse for the environment since their higher, more fuel efficient flight paths produce larger contrails
Contrails are twice as bad for the planet as planes’ carbon emissions, accounting for around 60% of aviation’s total climate impact. Researchers found that modern planes like the Boeing 787-9 Dreamliner (pictured) create more contrails than older models
Contrails are essentially clouds of ice formed as hot, humid air ejected from engine exhausts hits cold air in the upper atmosphere.
When the conditions are right, soot from the engine can become coated in water vapour and ‘seed’ the formation of ice crystals which produce larger clouds.
As these clouds linger in the atmosphere, they act like a silver emergency blanket, reflecting infrared energy back to Earth and preventing heat from escaping.
While their exact impact is hard to quantify, some studies estimate that contrails contribute around 60 per cent of the aviation industry’s total climate impact – double the impact produced by planes’ carbon emissions.
In this study, the researchers used satellite images taken from NASA’s GOES-R satellite to track more than 64,000 contrails from aircraft flying over the North Atlantic Ocean.
The researchers analysed more than 64,000 contrails over the North Atlantic. In these images you can see how the scientists filtered out all the contrails seen by the satellite (right) down to those they were able to obtain flight data for (left)
Contrails form when the soot from the engine gets coated in water vapour and then freezes in the atmosphere. In high humidity regions this then leads to crystals which create contrail and these merge with clouds to form ‘contrail cirrus’ clouds that can last for 18 hours. These clouds prevent heat from escaping and reflect it back to Earth, acting like a huge blanket
This contrail data was then compared to flight tracking information to examine how different types of aircraft created contrails.
The results revealed that newer, more efficient aircraft were producing larger contrails that lingered for longer periods of time.
Dr Gryspeerdt explains: ‘Newer aircraft are flying higher and higher in the atmosphere to increase fuel efficiency and reduce carbon emissions.
‘The unintended consequence of this is that these aircraft flying over the North Atlantic are now creating more, longer-lived, contrails, trapping additional heat in the atmosphere and increasing the climate impact of aviation.’
Since the thinner air in the upper atmosphere produces less drag, modern aircraft tend to fly at 38,000ft or higher in order to burn less fuel.
But as aircraft climb higher, they also encounter colder air which more frequently falls below the ‘threshold temperature’ at which contrails can form.
Older planes such as the Boeing 707 (pictured) which had its maiden flight in 1957, create fewer contrails since they fly at lower altitudes and produce cooler emissions
So, even though newer planes produce fewer carbon emissions from burning jet fuel, their overall environmental impact might be greater.
While the researchers point out that more efficient aircraft are obviously a good thing, the aviation industry faces a tricky balancing act between carbon emissions and the impact of contrails.
Dr Gryspeerdt says: ‘This study throws a spanner in the works for the aviation industry.’
The research also found the private jets of the ultra-wealthy were the biggest producers of contrails.
Private jets tend to fly above 40,000ft where there is less air traffic which puts them into even colder bands of air.
This graph shows the number of contrails detected relative to altitude for different types of plans. Planes older than 25 years old are shown in blue, planes less than 5 years old are shown in orange, and private jets are shown in green
Despite being smaller and burning much less fuel, the researchers found that private jets produce contrails comparable to those of larger commercial aircraft.
These contrails also last longer and so produce an outsized climate impact.
Dr Gryspeerdt says: ‘We already know that these aircraft create a huge amount of carbon emissions per passenger, so the super-rich can fly in comfort.
‘Our finding adds to concerns about the climate impact caused by private jets as poor countries continue to get battered by extreme weather events.’
Recently, global superstar Taylor Swift has faced increasing scrutiny for her use of private jets.
In 2023 it is estimated that Swift flew 178,000 miles via private jet, the equivalent of seven times around the Earth, and emitted 1,200 tons of CO2 in the process.
Private jets such as the Dassault Falcon 7X (pictured) used by celebs like Taylor Swift produce an outsized climate impact since they create larger and longer lasting contrails
Taylor has faced criticism for her use of private jets (pictured boarding in Kansas City) as it was revealed she produced 1,200 tons of CO2 travelling in 2023
With the disproportionately large impact of private jet contrails, Swift’s climate impact is likely even larger than previously estimated.
Yet the researchers note that there is a fairly simple fix to the problem of contrails.
Co-author Dr Marc Stettler says: ‘Our study provides the first evidence that emitting fewer soot particles results in contrails that fall out of the sky faster compared to contrails formed on more numerous soot particles from older, dirtier engines.’
Since soot from the incomplete combustion of jet fuel provides the nucleation point for ice crystals, cutting down on soot could mean fewer contrails.
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This means that cleaner, more efficient engines could help the airline industry cut down on both carbon emissions and the climate impact of contrails at the same time.
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