Aircraft emit a mix of gases and particles in the Earth’s atmosphere, near the surface and at altitude, up to 12 km. Aviation emissions degrade air quality in the vicinity of airports and globally, and contribute to climate change through pathways that are specific to emissions released at altitude, including but not limited to NOx-induced ozone, methane and stratospheric water vapour changes, and aerosol–radiation and aerosol–cloud interactions. These impacts remain uncertain, while the sector continues to grow at ~5% every year. At the same time, the atmospheric implications of mitigation options, including Sustainable Aviation Fuel (SAF) and hydrogen, are also not well understood, despite their high policy relevance.

This specialised session synthesises measurement and modelling contributions towards better understanding the present and future impacts of aviation emissions on atmospheric composition, air quality and climate, alongside the substantial recent progress on contrail research. We invite contributions on:
- the characterisation and quantification of gaseous and particulate emissions from current and future fuels, engines and combustor technologies, including ultrafine particles (volatile and non-volatile), lubrication oil and emerging or unregulated pollutants, based on laboratory, engine test-cell, airport and in-flight measurements as well as emission models and inventories;
- the atmospheric fate of these emissions: plume processing, transport pathways, chemistry, aerosol microphysics and removal processes;
- their air quality effects near airports and at regional and global scales, and the associated exposure and health implications;
- their non-CO2 climate effects through ozone, methane, water vapour and aerosol–radiation and aerosol–cloud interactions, including feedbacks, metrics and uncertainty assessment;
- the atmospheric implications of mitigation options, including fuel composition, sustainable aviation fuels, hydrogen and electrified propulsion, engine technology and operational measures.

We hope that these contributions will bring the community together and spark fruitful discussions and collaborations towards an improved understanding of aviation’s growing impacts on the atmosphere.