Aviation Non-CO2 Effects: Strategies for Minimizing Contrail Climate Impact

Greenhouse gas emissions from aircraft engines are one of two aviation sector climate impacts that must be mitigated as we approach midcentury. The other is contrails, the visible line-shaped clouds that form behind aircraft when flying at high altitudes, as those have been shown to contribute to surface warming at a rate similar to aviation carbon dioxide (CO2) emissions. While additional research is needed to more fully understand contrail related warming, it is abundantly clear that regardless of the exact impact non-CO2 effects like contrails must be minimized alongside GHG emissions if we are to significantly reduce the climate impact of aviation.

This paper introduces the concept of contrails, explaining what they are, how they form, and their climate impact. Following this, an overview is presented of potential mitigation solutions currently under consideration by the scientific community and the aviation industry, including the latest developments, opportunities, and challenges. Finally, we discuss our recommendations on how mitigations for non-CO2 effects can be integrated into policy.