A modest diet in our flying habits would be enough to level off the global heating caused by the aviation industry. That’s the surprising conclusion from a study, which also warns that if the aviation industry continues to grow at current rates then it will be responsible for around nearly 0.1C of heating by 2050.
Taking a flight adds to global heating in two ways. The first is from the direct effect of burning jet fuel and producing carbon dioxide, which remains in the atmosphere. The second is from indirect effects caused by tailpipe emissions in the upper atmosphere, resulting in cirrus clouds that trap additional heat and complex chemical reactions that alter the balance of greenhouse gases such as ozone and methane.
Working out how much global heating aircraft cause is complicated because carbon dioxide hangs around for thousands of years (meaning a flight taken in 1950 is still contributing to global heating today), while the indirect effects (clouds, contrails and the like) are much shorter lived – usually less than a year.
Milan Kloewer, from the University of Oxford, and colleagues from Manchester Metropoliton University took both the direct and indirect heating effects of aircraft into account to model the aviation industry’s contribution to global heating up to the year 2050. They found that to date aircraft are responsible for 0.04C of global heating: about 4% of the 1.2C temperature increase humans have caused since the Industrial Revolution. If aviation continues to grow at about 3% a year then it will have caused 0.09C of heating by 2050.
But their results, which are published in Environmental Research Letters, also show that if we were to reduce air traffic by just 2.5% each year (resulting in about 50% less air traffic by 2050 compared with 2019) then the aviation industry’s contribution to global warming would remain about 0.04C, resulting in a relatively insignificant amount of additional heating between now and 2050.
This is because more than half the warming caused by aircraft comes from the indirect effects – contrails, clouds and chemistry. And the fall in these indirect effects would balance out the warming caused by the continued rise in carbon dioxide.
“Any growth in aviation emissions has a disproportionate impact, causing lots of warming,” said Prof Myles Allen at the University of Oxford, a co-author of the study. “But any decline also has a disproportionate impact in the other direction. So the good news is that we don’t actually need to all stop flying immediately to stop aviation from causing further global warming – but we do clearly need a fundamental change in direction now, and radical innovation in the future.”