As the aviation sector continues its journey toward decarbonization, attention is increasingly shifting to non-CO2 emissions, particularly contrails—the cloud-like formations left by aircraft. These contrails, though short-lived compared to CO2, have been shown to contribute significantly to global warming. The growing recognition of their impact has led to new scientific studies and policy discussions, culminating in the first International Civil Aviation Organization (ICAO) symposium on non-CO2 effects in September 2024.
Understanding Contrail Climate Impacts
Contrails form when aircraft emissions interact with cold, humid air at high altitudes, often creating ice crystals. These can evolve into cirrus clouds that trap heat and contribute to climate warming. Although the warming potential of contrails is complex, current studies suggest that their contribution to global warming could rival, or even exceed, the impact of aviation’s carbon dioxide emissions.
However, unlike CO2, contrails are short-lived and not all contrails have a net warming effect. Factors like fuel composition, flight altitude, and atmospheric conditions play a significant role in contrail formation and persistence. For instance, sustainable aviation fuels (SAF), which have lower aromatic content, can reduce the likelihood of contrail formation, making them a valuable tool in mitigating non-CO2 climate impacts.
Mitigation Solutions: Strategic SAF Use and Rerouting
Mitigating the impact of non-CO2 emissions is now a central focus in aviation’s sustainability strategies. One proposed solution is the strategic deployment of SAF on flights most likely to produce contrails. Recent academic research and initiatives like the Flight100 transatlantic mission, powered entirely by SAF, have demonstrated the potential of this approach. By using SAF on targeted routes, airlines can reduce both CO2 emissions and contrail-related warming.
Another emerging solution is navigational avoidance—rerouting aircraft to avoid areas where persistent contrails are likely to form. The first large-scale trial took place in European airspace in 2021, where slight altitude adjustments were made for thousands of flights. While this method showed promise, it also highlighted the challenges of accurately predicting contrail formation. Advances in data analytics and predictive modeling, driven by collaborations with tech companies like Google and Breakthrough Energy, are helping to close this knowledge gap.
Policy Momentum: Tackling Non-CO2 Effects
In Europe, efforts to regulate non-CO2 emissions are gaining traction. From 2025, the EU Emissions Trading Scheme (ETS) will include a monitoring, reporting, and verification (MRV) system for non-CO2 emissions, alongside the ReFuelEU Aviation initiative, which mandates an increased supply of SAF. These regulatory frameworks are designed to address both carbon dioxide and contrail-related emissions, offering a comprehensive approach to aviation’s climate impact.
The Role of VURDHAAN in Aviation Sustainability
At VURDHAAN, we are at the forefront of supporting the aviation industry in navigating the complex landscape of non-CO2 emissions. Our expertise in areas like CORSIA, ReFuelEU Aviation, and Sustainable Aviation Fuels positions us to help airlines and aviation stakeholders understand emerging regulations and implement effective mitigation strategies. We work closely with our clients to ensure compliance with evolving policies while promoting sustainability and reducing their overall climate impact.
A Future of Collaborative Solutions
The growing focus on aviation’s non-CO2 emissions signals a shift toward more comprehensive climate strategies within the industry. While challenges remain—particularly in accurately predicting contrail formation and balancing fuel efficiency with rerouting—innovations in SAF deployment, data-driven decision-making, and policy frameworks are laying the groundwork for effective solutions.
As the global community continues to address both CO2 and non-CO2 emissions, the aviation sector has a unique opportunity to lead the way in climate action. With the right tools, strategies, and partnerships, the industry can mitigate its environmental impact and contribute to a more sustainable future.
At VURDHAAN, we are proud to be part of this journey, offering expertise and guidance to help our partners rise to the challenge of aviation’s evolving environmental responsibilities.