Climate change: How can we make flying greener?

Before the COVID-19 pandemic, when the global aviation sector soared in 2019, it contributed nearly 6 % to the planet-warming greenhouse gases in our atmosphere. A year later, as the industry was crippled by pandemic-related flight cancellations, that number dropped by 43 %. Last year it was still lower by 37 %. However, according to industry body the International Air Transport Association, air travel continues to increase. Greenhouse gas emissions are also growing. In response, the European Parliament announced a proposal to introduce environmental labels for air transport from 2025. The system should serve to inform passengers about the climate footprint of their flights. Carbon dioxide is responsible for only about one of the global warming effects attributed to air travel. Two-thirds are caused by other factors, most notably contrails, or contrails left behind by aircraft. Alternative flight paths could prevent contrails — those narrow white clouds that trace an airplane's path across the sky — that form when jet fuel, which contains kerosene, burns. At an average altitude of 8,000 to 12,000 meters (about 26,000 to 40,000 feet), the low temperatures cause water vapor to condense around the soot and sulfur that the jet emissions leave behind. The resulting ice crystals can remain suspended in the air for several hours. Contrails trap heat in the atmosphere, similar to a greenhouse, thereby greatly amplifying the impact of flying on the world's climate. Recent studies have shown that when it comes to global warming, contrails are about 1.7 times more harmful than CO2 emissions. On the plus side, condensation streaks are relatively easy to avoid. Using satellite data, flight planners can optimize aircraft routes to avoid weather conditions that promote contrail formation. Pilots can fly their jets, for example, 500 to 1,000 meters below, where temperatures are not so low. "It doesn't take a lot of effort to make these changes," said Markus Fischer, division director of the German Aerospace Center, adding that it would mean 1 to 5 % more fuel and flight time. But he told DW it would lead to a 30 to 80% reduction in the warming effect caused by factors other than CO2, he said. The European Union aims to include these non-CO2 climate impacts in future European emissions trading agreements. Airlines will have to start reporting such pollutants from 2025, according to a preliminary agreement in the European Parliament. (Gero Rueter, Microsoft Start)