Aviation's emissions are gaining a lot of public attention, with civil society being worried about climate change and its impacts. The industry's environmental performance is frequently scrutinized and air transport is regularly portrayed in the press as a major contributor to greenhouse gas emissions and a significant driver of climate change. Aviation today is responsible for approximately 2% of all man-made CO2 emissions and 3-4% of all man-made greenhouse gas emissions.
The reality is that as the number of flights increased yearon- year (pre-COVID-19), aviation's contribution to climate change had been growing steadily in absolute terms but remaining stable relative to other emission sources.
The need for a systemic approach to all aviation entities and cooperation
Aviation constitutes a multifaceted and interconnected system with a web of interdependencies. Beyond airlines, aviation encompasses aircraft and engine manufacturers whose innovations influence fleet efficiency and environmental performance. Airports facilitate passenger and cargo flows and themselves have a significant environmental impact. Air traffic control coordinates the aircraft movements, and any inefficiencies lead to extended flight paths. Maintenance Repair and Overhaul (MRO) organisations, ground handlers, equipment providers are only a few parts of the aviation systems, along with passengers and corporate travel.
By recognizing these diverse components and their interactions, policymakers should have a systemlevel thinking and develop policies that account for the entire aviation ecosystem, fostering a balanced approach that considers economic growth, environmental consideration, and social welfare. Following a systems perspective, policymakers can have a better-informed decisionmaking, identify potential synergies, recognise conflicts and trade-offs and implement multifaceted policy solutions for sustainable aviation.
There is a compelling need for better interconnection of sustainability policies in Europe, where the intersection of economic growth, aviation, and environmental responsibility is paramount.
Policies should be better interconnected
There is a compelling need for better interconnection of sustainability policies in Europe, where the intersection of economic growth, aviation, and environmental responsibility is paramount. This is even more critical when we recognise that aviation is a system. Having a siloed approach to address environmental issues limits the effectiveness of sustainability policies. By fostering further synergy among policies across various areas, such as engine standards and airspace architecture improvement, climate policy can be more effective.
Complementarity is an essential aspect of decarbonisation policies for aviation. This means that policies must work together to achieve the greatest possible reductions in emissions. There are various policies related to sustainable aviation with various levels of interconnection. An area that I have explored is the European Union's Emissions Trading System (EU ETS) for aviation, coupled with the Single European Sky initiative, that exemplify how regulatory frameworks can work in tandem. These two policies are not interconnected, but they complement each other. The EU ETS places a cap and trade on carbon emissions from flights incentivizing airlines to adopt cleaner technologies and invest in sustainable practices. Simultaneously, the Single European Sky initiative aims to optimise the airspace architecture, reducing congestion and shortening flight routes, thereby lowering fuel consumption and emissions. It is critical when we look at the effectiveness of the schemes to evaluate any cancel-out effects or double-counting in the reduced emissions attributed to each scheme.
EU ETS is now also better connected to Sustainable Aviation Fuel (SAF) in the form of offering 20 million SAF allowances to aircraft operators to incentivise the deployment of SAF as directed by the ReFuelEU blending mandate and financially assist the industry when the free ETS allowances are faced out from 2026. Similarly, though policies aimed at increasing the use of SAF (e.g., ReFuelEU) must be accompanied by supply-driven policies that aim to reduce the of SAF and increasing their availability.
In conclusion, European aviation policy needs to realise its full potential of approaching environmental sustainability policies in an interconnecting way to drive meaningful progress toward a more sustainable future while addressing environmental, economic, and societal dimensions simultaneously.
Regulation of Carbon emissions is only the start
When talking about sustainable aviation in terms of climate change, we think of carbon. Most sustainable aviation policies focus on reducing the carbon dioxide (CO2) emissions produced by aircraft fuel burn, with CO2 being a well-known contributor to climate change. We have achieved some significant progress on this thanks to the airlines push for fuel efficiency. Jet aircraft in service today are well over 80% more fuel efficient per seat kilometre than the first jets in the 1950s.
CO2 emissions are the most wellknown and well-understood aspect of aviation emissions, but non-CO2 effects such as contrails and cirrus clouds can also have a significant impact on the environment. As the scientific understanding of GHG is increasing, we need to realise that aviation decarbonisation efforts need to go beyond CO2, as according to EASA (2022), two-thirds of aviation's effect on climate is caused by non-CO2, with contrail cirrus alone accounting for up to 57% of the total impact.
Aviation produces black carbon emissions (soot) can contribute to localized warming and NOx emissions from aviation lead to ozone concentrations in the upper atmosphere, increasing radiative forming and contributing to climate warming. The climate impact of the non-CO2 emissions is dependent on the altitude and meteorological conditions and therefore is not related to the fuel consumption in a linear way. Therefore, addressing the fuel consumption does not resolve the non-CO2 effects; thus, they require further policy control.
There is a growing body of scientific research supporting the existence and significance of non-CO2 effects of aviation on the Earth's climate and policies need to consider this. The inclusion of non-CO2 emissions in the MRV of EU ETS is a positive step towards the right direction, but the non-CO2 emissions are still largely ignored in other sustainability and aviation policies. Establishing clear and ambitious emission reduction targets for both carbon dioxide (CO2) emissions and non-CO2 effects is vital.
The aviation industry has made significant commitments to achieving net zero emissions, but those commitments are only aspirational and not binding. Therefore, interconnected decarbonisation policies for aviation are critical to reducing greenhouse gas emissions and mitigating the effects of climate change. These policies must be complementary and consider both CO2 and non-CO2 effects and more importantly approach aviation as a system.