Aviation Non-CO2 Effects

The report examines non-CO2 aviation effects, specifically contrails, which contribute to surface warming at a rate potentially similar to CO2 emissions. It evaluates three primary mitigation strategies: reducing aromatics in conventional fuel, increasing SAF adoption, and implementing flight path deviations to avoid ice-supersaturated regions (ISSR). While fuel hydrotreatment can reduce soot, the report warns that the energy-intensive process may increase CO2 emissions, potentially offsetting climate gains. SAF is presented as a more effective long-term solution, with targeted use on high-impact flights offering 9-15 times the benefit of low-level global blending. Operational mitigation via AI and satellite-based re-routing shows promise, though it faces challenges from air traffic congestion and weather forecasting inaccuracies. The document concludes that a combination of these technologies and specific non-CO2 policies is necessary to reduce the sector's total climate impact.

• Contrails, formed in ice-supersaturated regions (ISSR), contribute to surface warming at a rate similar to aviation carbon dioxide (CO2) emissions and may represent one third or more of aviation's total climate impact.
• Hydrotreating conventional jet fuel to remove aromatics and naphthalene can reduce soot and contrail formation, but the energy-intensive nature of the process may increase CO2 emissions, potentially outweighing the climate benefits.
• Sustainable aviation fuel (SAF) reduces soot emissions and ice crystal formation; targeting a 50% SAF blend to the approximately 2% of flights responsible for the most warming contrails is 9-15 times more effective than blending 1-2% SAF across all flights.
• Real-time flight path deviation using AI and geostationary satellites to avoid ISSR is a viable mitigation strategy, with one trial involving American Airlines achieving a 54% reduction in contrails.
• Flight deviation strategies face significant operational hurdles due to airspace congestion, particularly on domestic routes in central Europe, making overnight routes from the eastern U.S. to the EU more suitable for initial application.
• Hydrogen-powered aircraft may increase the total volume of contrails due to higher water vapor emissions, but these contrails are expected to be shorter-lived and less warming because they lack the soot particles that act as ice crystal nuclei.
• The European Union is leading policy efforts to address non-CO2 effects through the EU ETS monitoring, reporting and verification framework starting January 1, 2025, and ReFuelEU reporting obligations for fuel suppliers.

APA

Sanchez, R. G., & III, T. K. W. (2025). Aviation Non-CO2 Effects. Clean Air Task Force. https://cdn.catf.us/wp-content/uploads/2025/03/18113117/contrails-report.pdf

Chicago

Sanchez, Rocio Gonzalez, and Thomas K. Walker III. Aviation Non-CO2 Effects. Clean Air Task Force, 2025. https://cdn.catf.us/wp-content/uploads/2025/03/18113117/contrails-report.pdf.

Wikipedia

{{cite report |last1=Sanchez |first1=Rocio Gonzalez |last2=III |first2=Thomas K. Walker |title=Aviation Non-CO2 Effects |publisher=Clean Air Task Force |date=March 2025 |url=https://cdn.catf.us/wp-content/uploads/2025/03/18113117/contrails-report.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{sanchez2025aviation, author = {Sanchez, Rocio Gonzalez and III, Thomas K. Walker}, title = {{Aviation Non-CO2 Effects}}, institution = {Clean Air Task Force}, year = {2025}, month = mar, url = {https://cdn.catf.us/wp-content/uploads/2025/03/18113117/contrails-report.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }