Issue Brief | The Growth in Greenhouse Gas Emissions from Commercial Aviation (2019, revised 2022)

by Jeff Overton (Environmental and Energy Study Institute) This issue brief examines the impact the growth of air travel and freight will have on greenhouse gas emissions. Subsequent briefs will feature the aviation industry’s emission mitigation efforts and commitments to reduce its contribution to climate change, as well as the effects of a warming planet on industry operations.

According to scientists who study aircraft emissions and their climate impacts, more research is required to fully understand the formation and impact of contrails and contrail-induced clouds so that mitigation strategies can be developed. One potential mitigation strategy is the use of sustainable biofuels blended with kerosene jet fuel, which is beginning to enter the commercial aviation market. Biofuels can have a significantly lower lifecycle greenhouse gas assessment than conventional petroleum-based jet fuel. Biofuel blends also reduce soot content, water vapor, and sulfates in the exhaust. Fewer particulates and less water vapor will mean a reduction in contrail formation. Reducing the sulfur content of kerosene jet fuel and engine design changes can also decrease exhaust particulates. Flight planning and altitude changes to avoid ambient conditions that produce contrails is another possible strategy. However, routing changes can create traffic problems and extend flights, adding to CO2 emissions.

Note: This issue brief was published in October 2019, but was revised in Spring 2022 to include more up-to-date information about the overall climate impact of aviation as well as the impact of the COVID-19 pandemic on commercial aviation recovery and growth. Previously, commercial aviation was thought to be responsible for approximately 5 percent of the world’s climate-warming problem. Newer research, using the metric “effective radiative forcing,” concludes aviation accounted for 3.5 percent of total anthropogenic climate warming in 2011, and likely in 2018 as well. According to the Intergovernmental Panel on Climate Change (IPCC), effective radiative forcing is a more accurate metric than radiative forcing as it is “a better indicator of global mean temperature response.” Scientists continue to acknowledge uncertainty in determining the influence of non-CO2 factors in aviation’s overall climate impact. The revision also reflects the United States’ adoption of ICAO’s carbon standard for commercial aviation aircraft in January 2021.