Flying is often pinpointed by environmentalists as being one of the most severe causes of climate change, with teenage activist Greta Thunberg shunning plane travel earlier this year when she crossed the Atlantic by yacht.

And Sir Elton John paid to offset the use of his private jet to fly the Duke and Duchess of Sussex around.

But a study has warned that travelling by aeroplane causes twice as much damage to air quality as it does to the climate.

The research from the Massachusetts Institute of Technology in America suggests it is even more damaging to air quality, with 16,000 deaths each year from poor quality air reportedly caused by plane emissions. 

Lead researcher Dr Sebastian Eastham, from the Laboratory for Aviation and the Environment in the institute’s Department of Aeronautics and Astronautics, said: “Aviation emissions are an increasingly significant contributor to anthropogenic climate change. They cause five per cent of global climate forcing.

“When you consider the full flight, which includes emissions from take-off, cruising and landing, aircraft emissions are also responsible for about 16,000 premature deaths a year from impaired air quality. 

“This is small compared to other sectors, being only about 0.4 per cent of the total deaths attributed annually to global air quality degradation, but is often overlooked in policy analysis.”

Attempts to address the climate and air quality impacts from aviation have traditionally come through policy changes, new technology or regulations to reduce carbon dioxide emissions.

But, the study notes, reducing one type of emission could come at the cost of increasing another, either in absolute terms, or by limiting potential reductions offered by new technology.

Dr Eastham said: “We could decrease nitrogen oxide emissions by designing engines with lower combustor temperatures. However, the resulting loss in thermodynamic efficiency would mean we need to burn more fuel, meaning more CO2. 

“These are the types of trade-offs that need to be quantified, and our study offers a fast way for decision makers to do this.

“We developed a set of metrics for comparing the climate and air quality impacts of aviation emissions at all flight stages, by estimating the social costs per unit of emitted pollutant. 

“The cost metrics are broken down by flight phase – cruising, landing and take-off – and by the geographical region of emission, both per kg of emission and per kg of fuel burn.”

The research team applied these metrics to evaluate the potential effects 
of a global expansion in aviation, consistent in magnitude with its current annual growth. It then used those findings as a benchmark for three scenarios.
Firstly, the researchers considered a scenario where fuel efficiency increases, and nitrogen oxide emissions reduce consistently in line with current 10-year goals.

Secondly, they looked at the trade-offs between climate and air quality impacts of engine-based nitrogen oxide emission reductions and, finally, they reassessed the climate air quality trade-offs of jet fuel desulphurisation.

Dr Eastham said: “Our results show three components are responsible for 97% of climate and air quality damages per unit aviation fuel burn:air quality impacts of nitrogen oxide at 58%; climate impacts of CO2 at 25%; and climate impacts of contrails at 14%. 

“It is important to note that the vast majority, about 86% in fact, of the nitrogen oxide impacts on air quality are due to the emissions from cruising, as opposed to the landing and take-off cycle. 

“These components - cruise NOx emissions, CO2 emissions, and contrails - are therefore primary targets for future strategies to reduce the atmospheric impacts of aviation emissions.

“To reduce the climate impacts of aviation, measures aimed at reducing CO2 emissions and contrails are likely to have the greatest net climate benefit. 

“In contrast, we found 94% of air quality impacts are driven by nitrogen oxide. 

“This suggests measures aimed at reducing nitrogen oxide emissions during cruising could lead to the greatest net benefits, even if they cause a small but uncertain climate nitrogen oxide drawback and a small decrease in fuel efficiency.

“Finally, we found the air quality impacts of aviation emissions significantly exceed the climate impacts, with air quality impacts being 1.7 to 4.4 times higher than the climate impact per unit of fuel burn. 

“This must be contrasted to ground-based industries, where post-combustion emissions control and access to cleaner fuels is widespread.

“For example, the climate impacts of the US power sector are of similar magnitude as the air quality impacts following significant declines in co-pollutant emissions over the past 15 years.”