Recognising the Full Climate Picture in Aviation
Moving Beyond the Carbon Narrative
The aviation industry has made significant progress in reducing carbon dioxide emissions. However, climate impact does not begin and end with CO2. In high-altitude environments, aircraft release a range of other emissions — including nitrogen oxides, water vapor, and fine particles — that interact with the upper atmosphere in complex ways.
These non-CO2 emissions contribute to radiative forcing and climate change through processes like ozone formation and contrail-induced cirrus clouds. Despite their major influence, these effects have often remained secondary in both research and regulation. This is beginning to change.
Introducing UNIC: A New Horizon for Non-CO2 Research
A Science-Led European Collaboration
On July 7th, the European project UNIC (Understanding NonCO2 Impacts from Decarbonised Aviation) officially launched under the Horizon Europe programme. Coordinated by ONERA, the French national aerospace research center, this initiative is supported by the European Union and the Swiss State Secretariat for Education, Research and Innovation.
The goal of UNIC is clear: to understand, measure, and model non-CO2 impacts from aviation, especially in the context of decarbonised fuels and technologies. It brings together eleven research and academic institutions across Europe and Canada, building a powerful collective for applied atmospheric science.
Why Non-CO2 Emissions Matter More Than We Think
Understanding Complex Interactions at High Altitude
Non-CO2 emissions can have a climate-warming effect equal to or greater than CO2, depending on the altitude, fuel type, and atmospheric conditions. Emissions like nitrogen oxides lead to ozone creation, while water vapor forms contrails that trap heat. Particulates also influence the formation and properties of these contrails.
Because these impacts occur in specific layers of the atmosphere, they require targeted study. General emissions accounting or low-altitude assumptions are insufficient. UNIC addresses this gap by focusing on real-time, high-altitude emissions data, combined with next-generation models.
Four Strategic Objectives of the UNIC Project
1. Development of Innovative In-Flight Sensors
To capture precise measurements of non-CO2 emissions, UNIC will design and deploy advanced sensors directly on aircraft. These tools will provide real-time, in-situ data during flight — enabling researchers to quantify emissions as they interact with the surrounding environment.
2. Evaluating Alternative Fuels in Real Conditions
Laboratory simulations and in-flight experiments will be used to assess the behaviour of Sustainable Aviation Fuels (SAF) and hydrogen. These studies will reveal how new fuels affect the production of non-CO2 emissions such as particulates and water vapour.
3. Improving Predictive Models for Contrail Formation
Current models for contrail prediction often lack the resolution needed for policy or operational planning. UNIC will integrate fine-particle data into contrail models, improving their accuracy and enabling more informed strategies to avoid persistent warming contrails.
4. Supporting Data-Driven Climate Policy
UNIC’s insights will be packaged into accessible, validated datasets to inform climate regulation. The goal is to provide scientific backing for decisions related to fuel certification, air traffic management, and long-term climate commitments in aviation.
ONERA’s Leadership Role in UNIC
Building on Experience from CLIMAVIATION
ONERA’s involvement in UNIC is a natural extension of its work under the CLIMAVIATION programme, a national-level research initiative supported by the French DGAC. In CLIMAVIATION, ONERA collaborates with IPSL (InstituteInstitut Pierre-Simon Laplace) to quantify the climate impact of aviation emissions, particularly focusing on non-CO2 effects.
In UNIC, ONERA is responsible for developing the core scientific tools that underpin the project’s modeling and sensor architecture. Their work ensures continuity between national and European research goals, creating an integrated framework that can adapt to future aviation technologies.
Relevance for the Wider Sustainability Landscape
Beyond Technology: Data-Driven Environmental Stewardship
As decarbonisation strategies continue to evolve, sustainability professionals face an increasingly complex matrix of emissions metrics. Projects like UNIC offer a more complete scientific foundation — one that recognizes the multi-dimensional impact of aviation and avoids over-simplified solutions.
By expanding our understanding of emissions beyond carbon dioxide, such initiatives contribute to smarter decision-making. They also highlight the importance of bridging the gap between scientific research and regulatory frameworks — a space where environmental consultancies are especially well-positioned to interpret, translate, and advise.
Conclusion: A Fuller Flightpath Toward Climate Responsibility
The Future of Aviation Demands Comprehensive Insight
UNIC signals a major evolution in how the aviation industry can measure, understand, and eventually mitigate its full climate impact. While CO2 remains a crucial metric, the atmospheric effects of non-CO2 emissions are too significant to ignore.
As global aviation transitions toward SAF, hydrogen, and other emerging solutions, projects like UNIC help ensure that progress is not just directional — but measurable, validated, and genuinely impactful. Understanding these nuances is key to building a climate-conscious transport sector that is both innovative and responsible.
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