Emissions produced by the aviation industry must be reduced each year if the sector’s emissions are not to increase warming further, according to the report.
The researchers behind the study, based at the University of Oxford, Manchester Metropolitan University and the NERC National Centre for Earth Observation, developed a technique to quantify the temperature contribution of historical aviation emissions, including both CO2 and non-CO2. The article also projects future warming due to aviation, based on a range of possible solutions to the climate crisis.
Lead author Milan Klöwer said: “Our results show that aviation’s contribution to warming so far is approximately 4% and is increasing. Covid reduced the amount people fly, but there is little chance for the aviation industry to meet any climate target if it aims for a return to normal.”
The only way to ‘freeze’ the temperature increase from the sector is to strongly decline carbon dioxide emissions by about 2.5% per year, the researchers found.
There is room for optimism, as they also showed that ensuring a 90% mix of low-carbon sustainable fuels by 2050 could achieve a similar outcome, with no further temperature increase from the sector. However, this relies on a sustainable production chain of low-carbon fuels that does not exist yet, said Klöwer. “The aviation industry has to come up with a credible plan for a 1.5˚C world,” he said.
“Any growth in aviation emissions has a disproportionate impact, causing lots of warming”, said co-author Professor Myles Allen. “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.”
Co-author Professor David Lee from Manchester Metropolitan University said: “These are important results that show stylised pathways of how we can get to where we need to be with aviation emissions, robustly showing the different roles of CO2 and non-CO2 impacts.
“One of the important nuances is that the non-CO2 impacts, like the formation of contrails and cloudiness, have been thought to dominate the total impact: this is true at present, but it’s not widely understood in the stakeholder community that if you take care of CO2, the non-CO2 fraction decreases in importance – even more so with sustainable alternative fuels that generate fewer contrails. This emphasises the importance of tackling aviation’s CO2 emissions.”
The solutions discussed in the study – such as moving to alternative fuels – could minimise warming, but will take time to implement. In the short-term, the researchers said there are actions that the industry can take right now.
Dr Simon Proud from the National Centre for Earth Observation and RAL Space said: “A ban on fuel tankering – where aircraft carry more fuel than they need, and hence burn extra fuel, to save the cost of refuelling at the destination – would reduce CO2 emissions in Europe alone by almost 1m tonnes.”
Other solutions, such as more efficient air traffic control and minimising holding patterns at airports, would also reduce emissions and help keep future warming minimal.
The research was published in Environmental Research Letters.
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