Aviation Non-CO2 Research Programme

This project investigates how SAF and hydrogen affect contrail formation and their overall climate impact. It combines laboratory experiments, advanced simulations and global aviation system scenarios modelling to quantify contrail ice properties, assess their radiative forcing, and evaluate mitigation pathways. The findings will inform policy and support strategies to reduce aviation’s non-CO₂ climate impacts.

SAFice aims to quantify how transitioning from conventional Jet A1 fuel to SAF changes the radiative impact of contrail cirrus. The project combines laboratory aerosol and gas turbine experiments with global contrail simulations to understand how different SAF usage scenarios affects ice-forming particles, contrail properties and atmospheric lifetime. By linking detailed measurements to large-scale modelling, SAFice will provide robust evidence on the climate implications of increased SAF use.

CRANE examines the climate efficacy of aviation NOx emissions, improving estimates of the ERF:RF ratio and associated global temperature responses under current and future scenarios. Using two Earth System Models (UKESM and WACCM/CESM2), it quantifies NOx-driven changes in atmospheric composition, radiative forcing, and climate response. The work reduces key uncertainties in non-linear chemistry–climate interactions and sectoral attribution. Findings will support evidence-based decisions by industry, regulators, and ICAO on future NOx controls.

COBALT addresses major observational gaps in contrail formation, persistence, and climate impacts. It combines high-resolution ground-based measurements in southern UK, novel satellite techniques, and detailed flight data to characterise the full contrail lifecycle. The project will generate a unique dataset to evaluate aircraft-scale and climate-model representations of contrails. Its outcomes will strengthen model reliability and inform contrail avoidance strategies and sustainable fuel trials.

REVEAL-NOx reduces uncertainty in the climate impacts of aviation NOx, a key Near-Term Climate Forcer. Using new in situ observations, advanced chemistry–climate models, improved emission inventories, and future scenarios, it constrains NOx radiative effects and associated trade-offs. The results will support robust, evidence-based pathways toward Net Zero aviation, recognising that eliminating NOx entirely is unlikely.

This project evaluates how future low-CO₂ aircraft designs influence contrail formation and climate impact, integrating turbulence/microphysics interactions into climate-optimised aircraft design. Advanced computational methods will quantify how alternative airframe and propulsion architectures affect contrail cirrus development. The resulting tools, embedded in open software and developed with industry partners, will guide technology choices that minimise overall future aviation climate impact.

GRIM-SAF uses a unique UK engine test-cell facility to generate contemporary total-emissions data from two engine types operating on conventional fuels and SAFs. It combines ground-based measurements with a UK-first in-flight ‘chase’ experiment to quantify real-world combustion and lubrication oil emission at engine-exit and within the evolving plume, and to evaluate their implications for contrail formation and local air quality. Outputs will improve emission inventories, atmospheric and climate models, and inform policy, regulation, and future low-emission engine design.

QR-CODE addresses the lack of observational constraints on aviation-induced cirrus. Leveraging COVID-era flight reductions, 20+ years of satellite data, and advances in machine learning and computer vision, the project will isolate aviation fingerprints on cirrus and contrails. It will generate the first large ensemble of observation-based constraints to improve aviation cirrus prediction and quantify climate effects. The results will support contrail avoidance strategies and inform trade-off mitigation pathways aligned with the UK Jet Zero strategy.

MAPLE aims to develop a robust framework for accounting for aviation non-CO₂ effects within climate policy using CO₂-equivalent (CO₂e) metrics. It will quantify uncertainties in different metrics, benchmark leading climate emulators (e.g., MAGICC, FaIR, LinClim, CICERO-SCM), and assess CO₂ trade-offs and temperature outcomes across scenarios and time horizons. The work will identify the most appropriate CO₂e approaches and estimate any additional CO₂ removal required to meet net zero targets. The results will provide policymakers with evidence-based guidance to minimising  the risks of perverse mitigation outcomes.

This project aims to reduce uncertainty in aviation non-CO₂ climate impacts by improving simulation of the two largest contributors: contrail cirrus and aerosol–cloud interactions. It will enhance the UK Met Office climate model to align with ECHAM and CESM methodologies, enabling consistent cross-model comparison for the first time. The project will assess future Net Zero-aligned scenarios, including SAFs, hydrogen, kerosene with direct air capture and storage, and contrail avoidance, supported by a global aviation systems model and the FaIR climate emulator. Results will guide technology, operational strategies, and policy decisions through close engagement with industry and government stakeholders.

Conlce aims to quantify how aerosols from next-generation sustainable aviation fuels and engine designs control contrail ice crystal number concentrations. It will quantify the fundamental aerosol activation parameters, predict contrail ice crystal emission indices, and deliver an open-source tool to improve contrail modelling and support industry in reducing contrail climate impacts.

AIRIC aims to improve understanding of how aerosol–radiation (ARI) and aerosol–cloud interactions (ACI) associated with aviation aerosols evolve under future scenarios, including SAF, hydrogen and contrail avoidance. It aims to reduce key uncertainties in aviation climate impact assessment and provide evidence to inform future technologies and climate policy.

TRITON uses novel computational methods to develop an efficient model of upper-tropospheric humidity. This will improve predictions of contrail formation and persistence, assess the impact of future changes to aircraft technology and improve the understanding of high cloud processes.

CRAFT assesses the impact of non-CO₂ aircraft emissions on the Arctic following the closure of Russian airspace, using recently launched EarthCARE satellite observations to measure aerosol emissions from flights high over the Arctic and track emissions to identify contaminated air and clouds. It’ll reduce uncertainty in aerosol–radiation and aerosol–cloud interactions, support impact-aware route planning, and advance satellite-based methods to monitor and track aviation aerosol emissions.

This project traces contrail formation from the first metres behind the engine to the point of climate relevance using high-resolution simulations. It examines how soot emissions from alternative fuels, fuel aromatic content, hydrogen combustion, and exhaust particles such as lubrication oil droplets influence ice formation. The project will provide high-resolution datasets to inform larger-scale contrail models, inform industry on non-CO₂ impacts of technology choices, and support policymakers in evaluating environmental trade-offs of future fuels and engines.

This project investigates how contrails from alternative fuels evolve within aircraft trailing vortices. It’ll address the roles of different particle types, trailing vortices, and fuel composition through a unique combination of Large Eddy Simulation and detailed microphysical modelling, alongside laboratory experiments generating artificial contrails using hydrogen and realistic SAF blends.

TRACE,  led by Airbus UK with inputs from Imperial College London , is developing modelling and analysis capabilities, together with sensor technology to better understand contrail effects and enable operational contrail avoidance. This project aligns with the Fuel Characteristics, Aircraft Systems and Knowledge, Data and Operations stream in the ATI Non-CO₂ Technology Roadmap.

QRITOS, led by Rolls-Royce with inputs from British Airways, Imperial College London and Heathrow, is exploring how limited supplies of SAF can be used more strategically, aiming to target SAF deployment towards the small proportion of flights that contribute most to climate impact.

OXCCU is assessing how its synthetic SAF (OXFUEL), produced directly from carbon dioxide and hydrogen using a Fischer–Tropsch catalyst, reduces soot and particulate emissions linked to persistent contrails. The project aims to evaluate the potential of this single-step process to produce jet fuel with improved combustion and reduced non-CO₂ impacts.

Honeywell is collaborating with Boeing and the University of Reading to develop a next-generation, aircraft-based humidity sensor prototype capable of providing more accurate, high-frequency atmospheric data than current commercial aircraft sensors. This data will help improve weather models, enhance contrail prediction, and support contrail avoidance strategies.