The Aviation Non‑CO₂ Expert Network (ANCEN) Task Group 4 has finalised a new report on ‘Gaps and uncertainties in aviation non‑CO₂ effects on climate’, which synthesises the current state of scientific understanding and identifies priority areas where further research is needed. This report is intended to support policymakers, regulators, industry and the wider scientific community as they work to assess and mitigate aviation’s non‑CO₂ climate impacts.
While aviation’s non‑CO₂ effects are known to contribute a large fraction of the sector’s effective radiative forcing, the associated uncertainties remain substantially higher than for CO₂. The report explains how these uncertainties arise from incomplete knowledge of the background atmosphere, gaps in observational data, limitations in process understanding and the way key processes are represented in climate models.
The report reviews the main sources of uncertainty across four major areas: contrails and contrail-cirrus clouds, indirect aerosol effects, NOx impacts on atmospheric composition, and smaller direct forcing components such as sulphur, soot and water vapour.
By clarifying where the largest knowledge gaps lie and which are most tractable, the Task 4 report provides a science‑based foundation for future research that is needed to enhance the assessments of mitigation options targeting aviation’s non‑CO₂ effects. It will inform upcoming ANCEN work on evaluating mitigation pathways and on distinguishing between uncertainties inherent to the underlying science and those introduced by specific mitigation strategies.
The report is available to download on the ANCEN website (section Task Group Reports)
