New Study Suggests Ways to Halve Airplane Emissions

Researchers show how aviation emissions could be cut in half by using existing technology and simple strategies.

That’s according to a new study led by the University of Oxford, England. These efficiency measures could be far more effective in tackling the fast-growing carbon footprint of flying than pledges to use “sustainable” fuels or controversial carbon offsets, the researchers said.

They believe their study, which analysed more than 27 million commercial flights out of approximately 35 million in 2023, is the first to assess the variation in operational efficiency of flights across the globe.

Researchers found an enormous variability in emissions efficiency. Some routes were shown to produce nearly 900 grams of CO2 per kilometre for each passenger - almost 30 times higher than the most efficient.

The study noted that business and first-class seats are up to five times more CO2-intensive than economy seats. Axing them - a scary proposition for most airlines - would boost passenger loads and offer big emissions savings quickly, it said. Upgrading to more energy efficient airlift would also yield significant CO2 cuts.

Aviation accounts for around 2.5 percent of global climate-heating emissions, but is rising. Decarbonising air travel remains a tough nut to crack as there is not yet a properly viable alternative to kerosine, and electric power is yet to be proven for large, long haul aircraft.

“Our results clearly show that efficiency-focused policy could swiftly reduce aviation emissions by more than half, without reducing flight numbers or waiting for future fuels,” said study co-author Dr Milan Klöwer from the department of physics at the University of Oxford. “These are tools that we can use right now.”

Add to this the results of a collaboration between American Airlines, Google Research and Breakthrough Energy which examined the climate impact of contrails, and the aviation sector really could, and swiftly, radically cut emissions. Contrails - the thin, white lines you sometimes see behind airplanes - have a surprisingly large impact on our climate. A 2022 IPCC report noted that clouds created by contrails account for roughly 35 percent of aviation's global warming impact, over half the impact of the world’s jet fuel.

In 2023, a group of pilots at American flew 70 test flights over six months while using Google’s AI-based predictions, cross-referenced with Breakthrough Energy’s open-source contrail models, to avoid altitudes that are likely to create contrails. After these test flights, Google analyzed satellite imagery and found that the pilots were able to reduce contrails by 54 percent.