Reduction in air transport emissions requires intensified efforts

"This progressive scenario already takes into account continuously improving aircraft technologies and additional efficiency improvements in en-route air traffic management," explains Markus Fischer, Director of Aeronautics Research at DLR. "The emissions-related analyses of the study show that the climate targets for air transport cannot be achieved by 2050 with the current state of research. Accelerated development of alternative propulsion concepts combined with SAF blending rates of 80 percent are needed for a significant trend reversal by 2050."

"In the Development Pathways for Aviation up to 2050 (DEPA 2050) study, we analysed two particularly likely scenarios for air transport up to 2050 in an interdisciplinary team," explains Project Manager Alexandra Leipold from the DLR Institute of Air Transport and Airport Research in Cologne. "Our conservative scenario assumes continued moderate technological developments in aircraft technology and horizontal flight efficiency. Despite those efficiency improvements, climate-relevant emissions will continue to rise due to the forecasted growth in air traffic. In addition, a progressive scenario with new technologies, processes and extensive use of sustainable aviation fuels at least points the way to reversing the trend in global air transport emissions despite growth." The DLR study examined in detail the expected future emission developments in both scenarios and the resulting climate impact with regard to aircraft technologies, air traffic management and SAFs.

Given the long development cycles in aeronautics, it is unlikely that there will be a comprehensive market penetration of emission-free alternative propulsion concepts based on hydrogen by 2050. Consequently, these are not included in the study. However, if development programmes and the market introduction of climate-friendly propulsion systems, especially with hydrogen as an energy carrier, are significantly accelerated, these technologies could significantly reduce the carbon dioxide emissions of global air transport ahead of the 2050 deadline. In the future, it will be necessary to investigate more closely how the climate impact of the non-carbon-dioxide emissions of these propulsion systems will turn out, for example, through the formation of condensation trails. The requirements that will arise with regard to the necessary infrastructure, such as with the introduction of electric and hydrogen-powered aircraft will also need to be assessed in more detail.

Challenge – reducing emissions despite air traffic growth

However, reversing the trend in greenhouse gas emissions from air transport remains a particular challenge given the projected long-term growth of the industry, and the lasting effects of the COVID-19 pandemic are still difficult to assess. Before the pandemic, the researchers had expected international passenger flights to roughly double from 31 million flights in 2014 to 61 million in 2050. Additional changes in connectivity and network design are expected to result from the market entry of supersonic aircraft and unmanned aerial vehicles in the air taxi sector from around 2030. The potential growth of these new market entrants was also examined as part of the study, based on forecasts of future aircraft movements and fleet development.