Like other countries, China’s civil aviation industry faces difficulties in fundamentally changing its aviation energy mix, which is primarily reliant on fossil jet fuel in the short term, and the large-scale application of deep decarbonisation technologies that balance availability and affordability. In the long term, as the most populous developing country, China has a vast potential demand for civil aviation transport, making the energy transition very challenging. However, a Five-Year Plan is underway for the green development of the industry. Against this backdrop is an insistence by China that the transition must be fair and equitable to developing countries, particularly regarding ICAO’s CORSIA scheme. Dr David Ma, an expert in Chinese civil aviation climate policy, analyses China’s current position.

As global climate issues intensify, countries around the world are formulating their own net-zero roadmaps in accordance with their national conditions. In 2020, China officially announced its climate goals of “striving to peak carbon dioxide emissions by 2030 and to achieve carbon neutrality by 2060”, incorporating climate change response as a national strategy.

In the following years, China issued guidelines and action plans at the national level, while key industries and sectors introduced implementation plans. The civil aviation industry, being a high-energy-consuming and high-emission sector, is one of the key areas that needs focused attention and improvement to achieve China’s “carbon peaking and carbon neutrality” strategic goals.

To address this, the Civil Aviation Administration of China (CAAC) released the ‘14th Five-Year Plan for Green Development of Civil Aviation’ in 2022, proposing the vision for green development by 2035, including a well-established green low-carbon circular development system, achieving carbon-neutral growth in air transport, and making green civil aviation a distinguished profile in the industry’s international exchanges, positioning China as an important leader in global civil aviation sustainable development.

Meanwhile, at the 41st Assembly Session of International Civil Aviation Organization (ICAO) held in 2022, the Chinese delegation expressed differing positions on the climate change resolution and the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) resolution of agenda item 18. They reserved their stance on the global international aviation 2020 carbon-neutral growth target, the 2050 net-zero carbon target for global international aviation, and the emission reduction mechanisms formed based on these targets, specifically on Articles 6, 7, 9, 17 of the climate change resolution, and the entire text of resolution 18/1 on CORSIA.

The delegation submitted a written reservation to the Secretariat after the meeting, stating they would decide whether and when to withdraw the reservation based on the progress of feasibility analysis of the above targets, the resolution of CORSIA fairness issues and the development of assistance mechanisms for developing countries.

Why does the stance of China’s civil aviation industry on climate change (mainly CORSIA) differ domestically and internationally?

International aviation emissions reduction is an integral part of global climate governance and should adhere to the fundamental principles of global climate governance, particularly the principles of common but differentiated responsibilities, equity and respective capabilities established by the United Nations Framework Convention on Climate Change (UNFCCC) and its Paris Agreement. It should align with the consensus on global climate governance models, allowing countries to independently choose mid-to-long-term goals and implementation pathways best suited to their national conditions.

The historical cumulative emissions of developed countries over nearly 200 years of uncontrolled industrialisation are the primary cause of current climate change. Developed countries have international obligations under the UNFCCC to significantly reduce greenhouse gas emissions ahead of developing and emerging market countries and to provide sufficient financial, technical and capacity-building assistance to developing countries.

China’s CORSIA position

In its working paper A41-WP/468 submitted to ICAO’s 41st Assembly, China explained its proposal to implement CORSIA through Nationally Determined Plans to Implement the CORSIA (NDPIC) and to establish a regular review method for CORSIA (see Figure 1 below). The document argues that to avoid any market distortions caused by CORSIA and to enhance the effectiveness of its implementation, a framework for a NPDIC should be established. This would allow each country to determine its own implementation rules and frameworks, subject to technical review by ICAO. Regarding regular reviews of CORSIA, the document proposes the establishment of a CORSIA Review Working Group, which would develop a set of evaluation metrics based on the guidelines for designing and implementing market-based measures (MBMs) provided in the appendix to resolution A40-18.

Figure 1: Framework of the Nationally Determined Plans To Implement The CORSIA (NDPIC) proposed by China

In working paper A41-WP/469, China elaborated on its stance and suggestions regarding the targets and measures for international aviation carbon emissions reduction. The document contends that the current CORSIA implementation plan and standards, which are based on ICAO’s goal of carbon-neutral growth starting from 2020 (CNG2020), do not conform to international law and the basic principles of global climate governance. It argues that if developed countries do not fulfil their international obligations under the United Nations Framework Convention on Climate Change (UNFCCC) through ICAO, developing countries will be deprived of fair development opportunities. The specific points are as follows:

In contrast to its stance at ICAO, China is cautiously advancing the implementation of market mechanisms domestically. The Civil Aviation Administration of China (CAAC) proposed in its Five-Year Plan in 2022 to “coordinate the construction of domestic and international carbon markets, and promote the establishment of a market-based carbon reduction mechanism for aviation activities.”

China actively promoting SAF

In contrast to CORSIA, China actively promotes SAF. In working paper A41-WP/468, China proposed that “countries refer to relevant ICAO standards or guidelines to determine sustainable aviation fuels and/or low-carbon aviation fuels recognised by their governments.” The Five-Year Plan aims to “promote breakthroughs in the commercial application of sustainable aviation fuels, striving to achieve an annual consumption of more than 20,000 tonnes of sustainable aviation fuels by 2025,” and targets a cumulative SAF consumption of 50,000 tonnes from 2020 to 2025.

It defines SAF as “aviation fuels that meet aviation airworthiness standards and sustainability evaluation standards for aviation fuels.” At the project level, it proposes to accelerate the establishment of a sustainable aviation fuel certification system and fully promote the construction of an airworthiness certification system for sustainable aviation fuels. It aims to conduct regular application demonstrations of sustainable aviation fuels, pilot blended supply models of sustainable aviation fuels at airports with an annual passenger throughput of more than 5 million in regions such as Beijing-Tianjin-Hebei, Yangtze River Delta, Guangdong-Hong Kong-Macao Greater Bay Area, Chengdu, Chongqing and Hainan, and support related airports in accelerating the construction of supporting infrastructure.

The latest news is that the CAAC has identified SAF, the carbon market and efficiency improvements as the three main directions for the green transition of civil aviation in the next five years (2025-2030).

The inconsistency between China’s domestic actions and international commitments on civil aviation’s climate change stance can be found in the Five-Year Plan. It pledges to: “Adhere to independent emission reduction actions, undertake emission reduction responsibilities commensurate with China’s national conditions, the development stage of civil aviation and its capabilities. Fully participate in the global governance process for sustainable development of international civil aviation, uphold the correct view of justice and interests, follow the principles of equity, common but differentiated responsibilities and respective capabilities, strengthen the application of international law, advocate for the establishment of a new international civil aviation emission reduction order with wide participation, independent contributions, mutual learning and benefit sharing, propose more Chinese solutions, promote a balance of obligations and rights, and demonstrate China’s image as a responsible major country.”

From this, several key points can be summarised:

■ Independent emission reductions and independent contributions.
■ The principle of equity and the extension to the principle of common but differentiated responsibilities and respective capabilities.
■ The ‘Chinese solution’.

Accelerating the energy transition

To achieve the goals of “carbon peaking and carbon neutrality”, China’s energy industry is steadfastly accelerating the energy transition, shifting the primary energy source from fossil fuels to non-fossil fuels. As a hard-to-abate sector, the civil aviation industry must make significant adjustments based on China’s macro situation to overcome resource and environmental constraints.

According to roadmaps by IATA, carbon emissions need to be reduced by 1.8 billion tonnes by 2050, with 65% of the emissions reduced through SAF, 13% through new engine propulsion technologies (such as hydrogen), 3% through efficiency improvements and the remainder through carbon capture and storage (11%) and offsets (8%). These measures are reflected in the Five-Year Plan.

Chinese civil aviation has positioned the energy transition, led by SAF, as a crucial node in fostering “new quality productivity” in the latest round of technological and industrial transformation, to achieve a new phase of high-quality development in civil aviation. This also demonstrates the significant role of Chinese civil aviation in building a community with a shared future for mankind. Therefore, China is very proactive and efficient in promoting SAF and other emission reduction measures, recognising that the issue is no longer whether to do it, but how to do it and how to do it well.

In terms of specific actions, due to the differences in national conditions and development stages compared to developed countries in advanced countries and the significant growth needed in the civil aviation transport market in the future, along with the two binding carbon targets of 2030 and 2060 set by the state, China has chosen more pragmatic independent actions, including emission reduction targets and measures. Chinese civil aviation’s vision is that every country should actively contribute to combating climate change but should make independent decisions based on their circumstances, rather than a one-size-fits-all approach.

Principle of equity

In its submitted position papers, China does not oppose the market mechanism of CORSIA, as it has already initiated a national emissions trading system, with civil aviation soon to be included. What Chinese civil aviation disputes is the lack of the principle of equity in CORSIA’s resolution and mechanism design. They often use this metaphor: requiring a growing teenager to diet along with an overweight adult is unfair.

The principle of ‘equity’ emphasises that the responsibilities and measures for emission reductions should consider the historical emissions, economic development levels and emission reduction capabilities of different countries. Developed countries that have competed industrialisation, having accumulated significant historical emissions during their industrialisation process, should bear greater emission reduction responsibilities and provide more financial and technological support. Meanwhile, developing countries need to gradually increase their emission reduction efforts based on their capabilities, promoting sustainable development.

Only on the basis of equity can countries achieve common but differentiated responsibilities and jointly address the severe challenge of global warming. An equitable emission reduction scheme not only promotes international cooperation but also ensures the well-being and environmental sustainability of people worldwide. This climate change principle contrasts with the ‘non-discrimination’ principle of commercial operations in international aviation. However, many developing countries, represented by China, unanimously demand that ICAO reflects the principle of equity in its emission reduction mechanisms.

Unfortunately, only textual confirmation is provided, and it is not reflected in the CORSIA mechanism design. If the climate change principle and aviation operation principle cannot be balanced within the ICAO framework, discrepancies in any emission reduction negotiations and discussions will persist.

China’s anticipated stance at ICAO’s next Assembly

At the ICAO 42nd Assembly in September 2025, China is expected to maintain its established stance, reiterating concerns regarding CORSIA, the implementation paths and standards associated with it, and the 2050 global international aviation carbon-neutrality goal. China believes these targets and pathways are inherently unfair and disadvantageous to developing countries.

Furthermore, because there is currently no intersection between ICAO’s work path and China’s, and with China effectively and confidently taking independent climate actions and involving its national ETS, China will persist with its established stance. The Chinese civil aviation sector will align with the national targets of “achieving carbon peaking by 2030 and carbon neutrality by 2060”, and will not prematurely declare that the aviation industry will achieve carbon neutrality ahead of schedule. Consequently, China will, to a large extent, not join CORSIA’s mandatory implementation phase in 2027.

The ‘Chinese solution’

Chinese civil aviation has made significant progress in responding to climate change and promoting sustainable development. Through the promotion of advanced fuel technologies, optimised route designs and enhanced air traffic management efficiency, China has significantly reduced carbon emissions. Additionally, Chinese civil aviation actively participates in international emission reduction initiatives, sharing experiences with global aviation organisations and counterparts to jointly address global climate challenges. With this series of emission reduction plans, Chinese civil aviation not only demonstrates a firm commitment to reducing carbon dioxide emissions but also strives to achieve significant results through practical actions. These efforts have enabled Chinese civil aviation to confidently push the ‘Chinese solution’, contributing wisdom and strength to the sustainable development of the global aviation industry.

China’s confidence in promoting the ‘Chinese solution’ includes not only technological innovation and operational efficiency improvement but also policy support and international cooperation. Through solid emission reduction actions and comprehensive emission reduction plans, China aims to establish a good international image and demonstrate its responsibility as a major country.

The introduction of the ‘Chinese solution’ will provide valuable experience and a model for the green transition of the global aviation industry, contributing to achieving global carbon neutrality targets. The solution will not only consider ICAO’s resolutions but also reflect its domestic climate change initiative actions, especially as the civil aviation industry is about to be included in the national ETS, which will significantly advance the deployment of CORSIA and SAF, a prospect worth looking forward to.

Photo (H. Goussé, Airbus): Air China A350-900

About the author

David Ma

Dr Xiangshan (David) Ma, who has long worked in China’s civil aviation industry, has been involved in tackling climate change and has experienced the historical transition of China’s civil aviation from energy conservation and emission reduction to carbon neutrality. After leaving the civil aviation industry, he has worked with the Global CCS Institute, Energy Foundation China, GIZ, and FutureCoal (formerly World Coal Association) on CCU/S and energy transition. Currently, he serves as an independent consultant on energy transition and climate change. He can be contacted at maxiangshan.2010@tsinghua.org.cn.

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Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

A lack of direction from governments worldwide, specifically in relation to the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), has left potential buyers in the Voluntary Carbon Market (VCM) in the dark, with many choosing instead the route of doing nothing – avoiding any potential complications or mis-purchases. However, the good news for buyers looking to invest in the VCM is that both the communication and regulatory landscape around carbon markets are improving, writes Tatiana Feuerhahn. We are seeing market proponents pushing for greater guidance in the VCM regarding what constitutes a “high quality” carbon credit, with the recent development by the Integrity Council for the Voluntary Carbon Market (ICVCM) of the Core Carbon Principles (CCPs) being a perfect example. We have also officially entered Phase I of CORSIA in 2024, with the aviation industry expecting greater guidance from the International Civil Aviation Organization (ICAO) in the latter half of the year regarding eligible emissions units (EEUs).

As a result, there is growing confidence among buyers. This increased clarity should boost demand and, as the price of carbon rises, make more projects financially viable. These initiatives coupled with the recent announcement by The White House, which has set out plans to develop robust standards for buyers and sellers of carbon credits in the VCM to help tackle ‘greenwashing’ and unlock green investment, will all help boost market sentiment and ensure that carbon markets can effectively support ambitious and credible climate action.

Aviation stands as a unique leader, being the only industry among the hard-to-abate sectors – such as steel, chemicals and cement, where it’s more difficult to lower greenhouse gas emissions – committed to achieving net-zero carbon emissions by 2050. This ambitious goal is accompanied by significant compliance obligations. ICAO requires airlines to mitigate most of the growth in their emissions beyond a 2019 baseline with eligible carbon credits. This requirement, a key facet of CORSIA, will become mandatory for all international operators, with a few exemptions, from 2027, following the current voluntary adoption phase.

Despite the sector’s strides towards reducing emissions through sustainable aviation fuel (SAF) and operational efficiencies, the current availability of SAF falls dramatically short of what is needed to power global commercial airlines, even for a single day. For instance, the recent deal by Emirates delivering 300,000 gallons of blended SAF from Shell Aviation to Dubai marks progress, but the lack of scaled availability is evident for today’s emissions. Moreover, the current regulations cap the maximum blend of SAF with conventional jet fuel at 50%, and most airlines use far lower proportions due to cost and supply constraints.

Carbon credit challenges

In order for the airline industry to meet its net-zero aspirations and current capabilities it must explore comprehensive strategies, including carbon offsetting, to bridge the gap. Currently, the demand for CORSIA-eligible products is expected to significantly outstrip supply by the end of the decade. Analysis by Abatable forecasts that demand could be between seven and fourteen times greater than supply, depending on the actions airlines take to cut emissions, as well as the development of eligible carbon registries and projects. This anticipated shortage underscores the urgency for airlines to improve their operational efficiencies and invest in new technologies. Yet, with major advancements like large-scale hydrogen storage and electric passenger planes still years away from being commercially viable, carbon credits remain a critical tool in the journey to net zero.

They provide a viable interim solution while technological advancements and increased SAF production capacities are developed. But navigating the environmental commodities market can be complex and challenging, particularly with the intricacies of CORSIA eligibility and the broader carbon market.

By working with a carbon market trading and advisory desk that is dedicated to assisting the aviation industry in its transition to a sustainable future, the industry can overcome the hurdles of decarbonisation and achieve its net-zero emissions goals. It can access expert advice on how to approach and manage emissions reduction efforts effectively, facilitate the acquisition and management of carbon credits, renewable energy certificates (RECs) and SAF credits, ensuring compliance and progress toward sustainability goals.

If the aviation industry leverages the existing expertise in carbon markets and sustainability, they can streamline emissions reduction efforts and meet the ambitious net-zero goals, contributing to a more sustainable future.

The aviation industry’s commitment to net-zero emissions by 2050 is a bold and necessary step towards combating climate change. However, the journey is fraught with challenges, particularly in the realm of carbon credits and sustainable fuel supply. The VCM will be instrumental in transitioning the aviation sector towards environmental sustainability.

About the author

Tatiana Feuerhahn
Valitera offers strategic advisory, principal trading, and portfolio management services to help clients navigate the complex environmental commodities landscape and seize market opportunities. Specialising in sourcing and trading carbon credits, renewable energy certificates (RECs), and sustainable aviation fuel (SAF). Formerly with Delta Air Lines, Tatiana is responsible for Valitera’s aviation advisory practice and has extensive experience in managing carbon credits and navigating CORSIA regulations. Her expertise helps Valitera’s airline clients to meet their environmental obligations and achieve net-zero targets. She can be contacted at tatiana@valitera.com.

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Top photo (Government of Guyana): In February, Guyana announced the world’s first credits eligible for use by airlines in the first phase of CORSIA

Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

For the “difficult to decarbonise” air transport sector, the advancement of sustainable aviation fuels (SAF) and alternative propulsion sources are well under way, along with technological and operational emissions mitigation measures. But even collectively they are likely to fall significantly short of the achievement of emissions reduction goals stemming from the Paris Agreement on climate change. Hence demand management will be necessary. Fiscal instruments such as taxes and frequent flyer levies fall foul of privacy and competitive issues, and notably of the economic regulatory framework unique to international air transport services. But capping emissions directly is feasible and would have definitive effect. Chris Lyle elaborates on the issues and puts on the table an emissions capping concept with airports as the nub in the context of the flights they enable.

The United Nations Framework Convention on Climate Change (UNFCCC), in pursuance of its 2015 Paris Agreement and basing itself on present scientific consensus, advocates that global greenhouse gas emissions will have to peak by 2025 and be halved by 2030 over 2019 levels, with an aim of ‘climate neutrality’ by 2050. Emissions from international air transport have been the subject of outsourced treatment by the UNFCCC, with the International Civil Aviation Organization (ICAO) as surrogate. However, they remain under the UNFCCC umbrella and, notably given the sector’s economic impact (and Scope 3 emissions generation), they are expected to meet the same goals – which are largely accepted by the industry, certainly as regards the longer term.

There is increasing evidence that existing aviation emissions mitigation measures are substantially inadequate for meeting these goals, whether shorter or longer term. Technological and operational improvements are levelling off and are being well outdistanced by traffic growth. Alternative propulsion sources to kerosene are in development, with electric (battery and hydrogen fuel cell) and hybrid electric expected to be significant in the 2030s, but only for shorter-haul and smaller aircraft. Gas turbine and liquid hydrogen, requiring considerable renewable energy and major structural change both in design of aircraft and in fuel delivery, are not expected to be widely in usage before mid-century.

SAF is the critical in-sector measure on which expectations are pinned, but bio-based sources face questions as to their full life-cycle benefits, limits on the supply of raw materials and considerable barriers regarding the necessary investment, economic pricing and scaling up to a commercial level. Synthetic e-fuels (also known as power-to-liquid), like biofuels, have drop-in capability, plus they do not emit any greenhouse gas emissions at all in operation. However, their prices are likely to remain in the order of three times, if not more, that of kerosene, they require massive scale-up and their production requires an enormous volume of renewable energy – and notably green hydrogen, for which there will continue to be limited availability and intense competition.

As well as privacy and competitive issues, fiscal measures come up against the economic regulatory framework for international aviation – the global Chicago Convention plus a network of around three thousand bilateral air services agreements and a few regional agreements. A large majority of these include legally-binding implications that restrict the application of emissions mitigation tools, particularly including taxation as well as other market-based measures.

Finally, out-of-sector measures such as carbon offsetting, capture and storage are frequently of questionable or unproven value and must be regarded as transitional in favour of real in-sector reductions in emissions.

All avenues of exploration and development of technology, propulsion and SAF should and will continue to be pursued, but it is already evident that even when all these measures are taken together there remains a pressing, paramount need for substantial additional action. Climate Action Tracker, an independent scientific analysis that follows government climate action and measures it against the Paris Agreement, found in June 2020 and confirmed in September 2022 that mitigation measures for international aviation were “critically insufficient”, compatible with a 4°C+ world.

A survey by GE Aerospace prior to the Paris Air Show in June 2023 showed that even the aviation industry itself was split on whether its own net zero 2050 goal was achievable, with under half of the 325 executives surveyed believing the industry will meet that goal. At the recent 2024 Annual General Meeting of the International Air Transport Association (IATA) there were several public remarks conditionally backing that goal, but the climate of optimism did not seem to have moved forward over the past year. Serious concerns were expressed that the achievement of various SAF goals – and notably that of ICAO’s aspirational reduction of 5% globally in carbon intensity by 2030 – were simply not achievable given the formidable issues of full life-cycle assessment, scaling up and pricing down.

In April of this year IATA produced a report, ‘The Aviation Net Zero CO2 Transition Pathways Comparative Review’,  which illustrated that there remain significant uncertainties regarding current routes and measures for achieving net zero. The 14 major global and regional net zero CO2 emissions roadmaps reviewed were based on differing assumptions, conditions and constraints. They all assume SAF will be responsible for the greatest amount of CO2 reductions by 2050, but their contribution varies from 24% to 70%. There are also differences in the forecast volume of residual emissions by 2050, which would necessitate continuing out-of-sector carbon capture or market-based measures.

Emissions capping rationale

In the light of the above, the need for specifically capping aviation operations has now come on the radar. For example, a comprehensive research report in 2023 by the Travel Foundation found only one scenario for travel and tourism to achieve net zero by 2050 and that incorporates slowing the growth in air transport, including capping long-haul flights (over 3,500 km) to 2019 levels.

Capping air transport emissions themselves – rather than the number of flights or through pricing mechanisms with their imprecise effects – would be direct and with a definitive impact. Imposition of a structure for capping emissions consistent with the Paris Agreement goals would proffer pre-determined limits and, coming into play when other measures are insufficient, would be a principal driver of mitigation. The conundrum is finding the most effective way to do this.

Irrespective of the ‘ownership’ of flight emissions – generally attributed to passengers/shippers and particularly air carriers, to whom mitigation action is today predominantly addressed – the best origin for capping the emissions is the airport. And the prevalence of self-interest and privacy issues for passengers/shippers, airlines and other market players means that government regulation is necessary. Emissions capping action with airports as nexus is feasible within the existing regulatory framework and could be most effective. 

Blending mandates for SAF are effectively airport-oriented and amongst recent examples one by the Singapore government is of particular interest. In February 2024, it announced SAF blending targets for departing flights to be applied from 2026, in this case to be partly funded by a levy on passengers which will vary according to both class of travel and distance (in bands). This initiative falls within both the environmental and the economic regulatory frameworks for international air services – as could emissions capping action based on airport departures. Different circumstances apply from the 2023 Amsterdam Schiphol flight capping proposal, which was aimed essentially at noise and local air quality rather than emissions reduction and came up against the globally agreed ‘balanced approach’ to aircraft noise management. 

At present, emissions assessed for airport accountability are limited in compass. Emissions ascribed to airports can be restricted to the Scope 1 airport operations, although increasingly they include a component of Scope 2 emissions. However, and crucially, they do not include emissions from the flights that the airports empower. Also, emissions from international flights are presently treated separately from those generated by domestic flights and from the not insubstantial emissions generated by local ground transportation and business created around airports by all flights.

Airports could become key enablers in aviation emissions reduction if their accountability were to move to a form of Scope 3 which had the extent of including emissions from the flights departing their runways to their first destination, whether domestic or international.

Capping emissions, not flights

A climate-based approach could be to cap not simply the number of flights but rather the volume of emissions from the first leg of all departing flights, whether by passenger, combi or freight aircraft. Data regarding CO2 from domestic operations should be readily accessible at the national level and data from international operations, in total and for individual routes, are available through various sources, notably including the Monitoring, Reporting and Verification system of ICAO. While not government instituted, the necessary information is also accessible from entities such as Google Flights and Travalyst. For the 1,300 largest global airports it has already been packaged since 2019 by Airport Tracker, a project attempting to visualise the climate impact of airports worldwide. In cases where data may be incomplete, emissions evaluated from fuel uplifted by flight could be used as a surrogate.

The capping approach – for an airport or for a group of airports serving the same city – could follow the UNFCCC direction by starting with the 2025 emissions peaking and being reduced annually through to half the 2019 levels in 2030. Beyond that time frame is presently aspirational and somewhat speculative. Parameters to apply beyond 2030 could be made at a later date; similarly, targets for non-CO2 emissions could be incorporated once a more definitive impact for them is accepted – although applying limits on CO2 emissions would automatically cap non-CO2 pro rata.

The table below, with data developed from Airport Tracker and flight search engines, illustrates the stark reality and enormity of such a challenge. The data are representative of the first leg of outbound flights for a typical large European airport (adjusted for illustrative purposes to a round total of 10 MtCO2 emissions for 2019 and hence half that, 5 MtCO2, for 2030). There is an assumed overall percentage increase of 3% in emissions for 2025 over 2019. A single capping reduction is here applied across the board, irrespective of distance. As shown, for the 2019 base year, 19% of departing flights were over 4,000 km but they produced 66% of the emissions. The contribution of long-haul is actually significantly higher than this at major hubs such as Paris Charles de Gaulle, Frankfurt or London Heathrow.

There would evidently be little room for manoeuvre of capping amongst distances given the dominant emissions contribution of long-haul. Nevertheless, the application might be tweaked according to individual country circumstances and policy, for example by division into two or three flight groups according to distance bands with differing capping reductions, by providing partial exemptions to key long-haul routes, or by taking into consideration carbon intensity (lower for longer haul). Where the concept covers a group of airports, different levels could be applied to each airport in reflection of differing market segmentation.

In pursuance of climate justice and the UNFCCC principle of Common but Differentiated Responsibilities, exemptions could be given for flights to and from Least Developed Countries, Landlocked Developing Countries and Small Island Developing States, with the cap(s) for other flights being reduced pro rata.

The procedure for application of the caps would, as today, be through the airport slot allocation process. While allocation based on emissions generated by a flight, rather than simply the flight itself, would add a dimension of complexity to the process, this would be well within the bounds of practicability, with likely fewer flights and little effect on timings.

Action could be taken nationally, with the level of capping or reduction determined in the context of other emissions mitigation measures in place for the country concerned. Such a national approach, if carefully designed and applicable to all carriers at an airport, would not breach the Chicago Convention or air services agreements. Even action by a handful of countries would help, preferably in a co-ordinated framework.

While the increasing plethora of SAF initiatives is encouraging, along with alternative propulsion sources for the longer term, regulatory capping action on reducing aviation emissions will almost certainly become, or remain, necessary for the Paris targets are to be achieved. With the need for CO2 peaking now only a year away, addressing such capping is well overdue. This article was developed with a view to encouraging debate, research and advocacy accordingly.

About the author

Chris Lyle, FRAeS
Chris is a veteran of British Airways, the UN Economic Commission for Africa, ICAO, UN Tourism (as Representative to ICAO) and his consultancy Air Transport Economics. He has been involved in policy on mitigation of aviation’s climate change impact for over 25 years. He can be reached at clyle@airtransporteconomics.ca

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Editor’s note: Chris insists this is his last article for GreenAir and is taxiing off into the sunset after many years of contributing not just thoughtful Commentary op-eds on tackling the challenge of aviation’s impact on the climate but also the insights he shared from his vast experience of international aviation climate policy that stretches back to the adoption of the Kyoto Protocol in 1997, when he was a senior official at ICAO. We wish him and his wife Linda a long and happy retirement.

Top photo: Heathrow Airport

Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

Travel and tourism represents directly some 3.5-4.0% of world GDP and employment and around 5% of CO2 emissions. Air transport is increasingly dependent on tourism – and tourism has been making increasing use of aviation, particularly internationally. But despite their symbiotic relationship, on greenhouse gas emissions mitigation the two components essentially operate in policy silos at both national and global levels. Chris Lyle reviews recent studies including a seminal and wide-ranging Stocktake by the Tourism Panel on Climate Change undertaken to assess progress on sector climate action and provide insight for advancing climate resilient tourism development worldwide. Present inadequate mitigation action, potential implications and pathways for tourism are addressed here, including the need for integrated tourism and aviation policy.

As a complement to the first Global Stocktake by the United Nations Framework Convention on Climate Change (UNFCCC) concluded at COP28 in Dubai in December 2023, the Tourism Panel on Climate Change (TPCC), an independent science-based collaboration, released a complementary Tourism and Climate Change Stocktake at the sectoral level. Aviation is the single increasingly dominant contributor to travel and tourism emissions, particularly at the international level, and the TPCC has recently also issued a Horizon Paper (by this author) that takes a comprehensive look at related mitigation policy regarding international aviation emissions. Both documents are available as downloads on the TPCC website.

Also in 2023, a report, Envisioning Tourism in 2030 and Beyond, published by the Travel Foundation, addressed aviation emissions in the changing shape of tourism in a decarbonising world.

The TPCC and Travel Foundation publications are the first global assessments of travel and tourism’s contribution to climate change and mitigation options to encompass international aviation since the definitive study, Climate Change and Tourism – Responding to Global Challenges, published in 2008 by the UN World Tourism Organization (now UN Tourism) with the UN Environmental Programme and the World Meteorological Organization. These studies produced critical findings in relation to the aviation and tourism nexus.

First, tourism has seen significant growth and is continuing to grow faster globally than the rest of the economy, putting greater pressure on the need to decouple growth from emissions. Continued capital investments and trends toward longer average travel distances and more air travel are key barriers to emission reductions. Tourist transport emissions increased by 65% between 1995 and 2019. Air travel was a key driver of this growth, now contributing 26% of all tourist trips (domestic and international) but 75% of tourist transport emissions. Aviation contributes 40% of the GHG emissions of tourism overall and at least 60% of the emissions from international tourism.

Existing technologies are unlikely to mitigate aviation emissions fully by the aspirational target of 2050. Sustainable aviation fuels (SAF) can contribute to mitigating aviation’s climate impact, but their net greenhouse gas improvement, broader sustainability, scalability and climate justice implications will constrain production. Emerging technologies will play an expanding role after 2040.

Neither tourism nor aviation policy is yet integrated with global and national climate change frameworks, despite an increase in sectoral climate pledges. Only 18% of the UNFCCC’s Nationally Determined Contributions (NDCs) and 43% of National Adaptation Plans submitted over time address tourism. Tourism is omitted from climate change frameworks in many countries where the sector represents a high proportion of the economy. Few parties currently incorporate international aviation emissions in their NDC filings, although these include the EU and its member states and some others have indicated their intention to do so.

The separate treatment of domestic and international aviation is a governance challenge for effective mitigation policy. International aviation emissions policy (but not domestic) has effectively been outsourced since 1997 by the UNFCCC to the International Civil Aviation Organization (ICAO), whose action is significantly circumscribed by its regulatory dictate.

The Travel Foundation study found only one scenario for travel and tourism to achieve net zero by 2050 and that incorporates an increasingly substantial contribution of SAF, revolutionary zero-emissions technology entering the air transport market from 2040 onwards and slowing the growth in aviation – including capping long-haul flights (over 3,500 km) to 2019 levels.

Demand management in the form of emissions capping of air transport is likely to become necessary sooner rather than later if the Paris Agreement targets are to be met, and early evaluation of options should help to minimise the economic and social impact.

National/local action

More and more tourist destinations are becoming aware of the need to mitigate climate change and local entities –  mostly SMEs, including hotels, tour operators and car rental companies – who are actively working to reduce emissions under the umbrella destination management of tourism authorities. But these efforts are most frequently subsumed by the emissions contribution of flights to and from the destination, which are rarely if ever addressed by tourism bodies. A critical issue here is the extent to which the respective tourist provider and receiver parties should be responsible for the flight emissions.

Aviation and tourism were both devastated by the Covid pandemic. But while the aviation sector has been focused on build back and growth, tourism started its recovery earlier through domestic travel, and some parts of the tourism industry are engaged in taking a broader perspective, rethinking the tourism model. Many destination countries are concerned about low retained revenue yield and negative impacts on local communities and facilities.

One aim is also to restore balance between ‘overtourism’ and local quality of life, including reflection of the national environmental and ecosystem sustainability promoted through welcoming international tourists. More generally, tourist destination countries are encouraging longer stays and less frequent visits, non-peak travel and alternative destinations within the same country, as well as imposing restrictions, for example, on access to attractions and accommodation (notably AirBnB), hotel construction and fast-food outlets.

However, there is as yet no indication of whether this focus on higher quality, higher priced tourism with less attention to traffic volume will have a significant impact on air transport. Many destinations still have an approach of ‘build it and they will come’, facilitated by the aviation focus on growth.

Global framework

There are significant legal differences globally between both the environmental and the economic regulation of aviation and those of tourism. As regards greenhouse gas emissions, tourism and domestic aviation (including airports, associated ground transportation and locally related business) are treated directly under the UNFCCC while international air transport emissions mitigation policy is dealt with by ICAO. Equal application provisions in the latter Organization’s governing Chicago Convention continue to dog climate change discussion and agreed action tends to be ‘least common denominator’ and diffuse, with no direct accountability to any individual country.

In 2019 the ICAO Assembly adopted CORSIA, a global carbon offsetting scheme, followed in 2022 by a long-term global aspirational goal (LTAG) for the Organization and its member states to work together to strive to achieve net-zero carbon emissions for international aviation by 2050. However, no intermediate goals have been set and pathways towards the 2050 goal will only be established in 2025.

International aviation had come back into the UNFCCC mainstream in 2021 at COP26 in Glasgow, if only at a side event initiated by the United Kingdom host, where an International Aviation Climate Ambition Coalition (IACAC) was set up, presenting a declaration calling for “ambitious actions to reduce aviation CO2 emissions at a rate consistent with efforts to limit the global average temperature increase to 1.5⁰C.” As with the ICAO LTAG (which it preceded) the IACAC declaration, with an updated version currently signed by 59 States, has no intermediate goals or pathway backup.

The silo split between aviation and tourism was reflected at COP26 in that a Glasgow Declaration on Climate Action in Tourism was adopted separately. The Declaration is currently signed by over 850 private sector organisations, predominantly SMEs and tourism marketing entities – but from the whole aviation sector only a single airport. Consistent with UN Tourism and the World Travel and Tourism Council (which is a signatory) the Declaration is aimed at a “global commitment to halve emissions by 2030 and reach Net Zero as soon as possible before 2050.”

Differences in economic as well as climate change regulation between tourism and aviation add to the intricacy. Both international and domestic tourism are subject to the trade in services rules of the World Trade Organization. But international air transport is generally governed by around 3,000 bilateral air services agreements and a few regional agreements, many of which include legally-binding implications affecting emissions mitigation tools, for example on taxation. This complex regulatory framework has to be accommodated when developing economic measures for reduction of air transport emissions, particularly in the case of international operations.

ICAO and UN Tourism have recently increased cooperation “to strengthen the relationship between air transport and tourism in research, policy and management areas, improve coordination on efficient border management priorities, and support travel and tourism recovery and transformation in light of the climate change imperative.” At the same time, one of ICAO’s objectives for 2024 is to “collaborate with the United Nations World Tourism Organization and global tourism boards to promote travel by air.”

For its part, UN Tourism has developed a Statistical Framework for Measuring the Sustainability of Tourism, “an organizing structure for integrating statistics on the economic, environmental and social dimensions of sustainable tourism.”  But the current (February 2024) version barely even references air transport – and ICAO only in a single footnote.

Demand management

The UNFCCC, basing itself on present scientific consensus, advocates global greenhouse gas emissions will have to peak by 2025 and be halved by 2030 over 2019 levels, with an aim of ‘climate neutrality’ by 2050. Emissions from the international air transport sector, given its economic role, Scope 3 generation and UNFCCC treatment, are expected to follow the same goals – which are largely accepted by the industry, certainly as regards the longer term.

All avenues of exploration and development of technology, propulsion and SAF should and will continue to be pursued, but there is increasing evidence that even when all these measures are taken together they are substantially inadequate for meeting the above goals, whether shorter or longer term. There remains a pressing need for substantial additional action. There are therefore increasing calls for demand management. Fiscal measures face significant obstacles in the form of the economic and environmental regulatory structure of international aviation and thus the concept of specifically capping aviation operations is now on the radar. Imposition of a structure for capping emissions consistent with the Paris Agreement goals would provide definitive limits and, brought into play when other measures are insufficient, would be a paramount driver of emissions mitigation. A viable emissions capping approach within the regulatory framework governing civil aviation is discussed in this author’s article published by the Responsible Tourism Partnership.

As regards demand management in addition to most other emissions mitigation measures, the UNFCCC principle of Common But Differentiated Responsibilities and Respective Capabilities (CBDR) is fundamental. In particular, there are many Least Developed Countries (LDCs), Landlocked Developing Countries (LLDCs) and Small Island Developing States (SIDS) very much dependent on aviation for their tourism sectors, the employment it creates and the foreign currency it brings. While they make up only 5.4% of all tourism transport emissions they deserve special treatment in the name of climate justice. They need a better mechanism for determining and realising their national interest in weighing up the benefits and costs of aviation-dependent tourism to their countries. Also in pursuance of CBDR, and taking a leaf from ICAO’s CORSIA, routes to and from these countries could at least transitionally be exempted from emissions capping.

In that context, research could be initiated on evolution of ‘essential air services’, linking the environmental pillar of sustainability with the economic and social pillars. The concept of such services has long been defined and given special regulatory treatment in a number of domestic jurisdictions and it is not too early for the travel and tourism community to start thinking about working towards their development for widespread international application (for a descriptive methodology see the UNWTO initiated study by ICAO on An Essential Service and Tourism Development Route Scheme). At some point, those small volume destination countries without a national airline may need to (re)assess the need for one, at least for operations to and from nearby major international hubs.

The bottom line

The tourism sector should take much greater responsibility for the emissions caused by the demand for aviation that it generates. For example, destinations should evaluate the options for focusing on geographically nearer originating markets. The sector also needs to get much more directly involved in the decarbonisation of aviation, particularly international aviation, and to address ways forward against the risk of the industry becoming a distressed or even stranded asset. In evolving tourism models, industry and destinations should integrate international aviation emissions into assessments and actions to mitigate climate change.

The initiative will have to be taken by tourism authorities and the tourism industry, including through entities such as the UNFCCC, the World Economic Forum and the World Travel and Tourism Council – the aviation side needs to be nudged beyond its silo.

Chris Lyle

A long term veteran of aviation, Chris is currently a Lead Expert in the Tourism Panel on Climate Change (TPCC). He acknowledges with thanks the comments on a draft of this Commentary by Susanne Becken, Geoffrey Lipman and Paul Peeters of the TPCC. He can be reached at clyle@airtransporteconomics.ca

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Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

This year begins with a reflective assessment of the aviation sector’s climate credentials and the challenges it faces, write Jarlath Molloy and Finlay Asher, who point out this may not be an easy read for some, as there are many barriers to overcome. The strategy so far has been to stick our heads in the sand and ignore these, they say. Yet there are pathways to a safe landing and the costs of doing something are less than the costs of doing nothing. In this article the authors look to shine a spotlight on aviation’s full climate impact and how the sector alone could put us over the 1.5°C goal of the Paris Agreement. They highlight the common failings of the sector’s hypothetical decarbonisation pathways and propose an alternative to the sectors’ net zero aspirational goals – which will feel radical to industry leaders but are consistent with how other sectors are setting science-based targets.

As a group of scientists, engineers, air traffic controllers, pilots and airline workers, climate change keeps Safe Landing members up at night. We worry about the future and our legacy to our children. Meaningful action and change is frustratingly slow, despite all the warnings about planetary boundaries^[i], tipping points^[ii] and the costs of inaction in response to climate and biodiversity crises. We should have the confidence to critically ask ourselves whether the sector’s environmental practitioners can have any hope in terms of impact, relevance or effectiveness^[iii].

Aviation greenhouse gas (GHG) emissions reached one billion tonnes of CO₂ emissions pre-Covid^[iv] and are expected to pass this again in the near future^[v]. This threshold is also known as a ‘carbon bomb’. But of course the bomb is even bigger because most of the sector has historically refused to recognise its non-CO₂ emissions impact. While it is true this is more complex to measure^[vi], the data and tools exist to assess the full climate impact the aviation sector is responsible for^[vii] and to confidently reduce non-CO₂ emissions.

How did we get here? This problem has been 30 years in the making. Heads of states from around the world agreed the formation of the UNFCCC in 1992 at the Rio Earth Summit and to stabilise GHG emissions in the atmosphere to “prevent dangerous anthropogenic interference with the climate system”. Action on aviation GHG emissions was deferred by giving the problem to ICAO. In 2015 the Paris Agreement refined our collective ambition to limit climate change to 1.5°C this century, with GHG emissions to peak “as soon as possible” and reach net zero by 2050.

It took exactly 30 years from the Earth Summit at Rio for governments (and industry) to set GHG emission targets for the aviation sector, in 2022, but which are still only aspirational^[viii] and fall short of what is required to achieve the Paris Agreement’s 1.5°C temperature goal^[ix]. This was in spite of ICAO commissioning a special report from the UNFCCC on aviation’s climate change impact in 1997^[x] and a slew of scientific studies and research since then on the same topic. Despite its name, ICAO’s flagship initiative known as CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation)^[xi] won’t reduce[^xii] aviation GHG emissions. Instead, it relies on offsets from other sectors to keep carbon emissions from international flights below a 2019 baseline.

The gap to the 1.5°C temperature goal linked to avoiding the worst of climate change impacts is only 0.3°C. The aviation sectors’ growth plans alone may use this up, once we count its CO₂ and non-CO₂ emissions, i.e. its full climate impact^[xiii]. Ratings agencies are already assessing Environmental Social & Governance (ESG) risks and performance across the sector and it’s only a matter of time before attention shifts to assessing climate transition risk and the sector’s prospects in a world where carbon budgets are being set, for example in the UK^[xiv] from the 2030s. Likewise, it’s possible that CDP (formerly Carbon Disclosure Project), the Science Based Target initiative (SBTi), activist shareholders and others begin to loudly call out the sector’s omission of its non-CO₂ impact and apply much greater scrutiny to the credibility of the sector’s decarbonisation plans. This includes the role of offsets and the availability of sustainable aviation fuels (SAF) at the quantities required to make a material difference to the sector’s GHG emissions without exacerbating climate impacts elsewhere^[xv]. Continuing high profile examples of climate-related loss and damage will further catalyse public opinion and keep these issues on the agenda.

The sector is often referred to as one which is difficult to abate. This isn’t entirely correct; industry leaders know how to reduce its climate impact – they have just chosen other priorities for 30 years. Two of the biggest barriers to change include groupthink and the short-term cost of change. Until this is addressed and industry leaders are incentivised to do the right thing, we’ll continue to see the sector try to bat away ever increasing concerns about its climate change strategies.

One approach used to date is the role of lobbying of policymakers against proposals that might affect their economic prospects^[xvi], while simultaneously marketing aviation’s services relying on ‘tropes’ including adventure & discovery, privilege and urgency (albeit not climate urgency)^[xvii].

Another approach is to issue decarbonisation roadmaps. Numerous industry-led and other reports have been published since 2020. Few, if any, are independently peer-reviewed or published in scientific journals. None of them have reconciled the sector’s full climate impact with the temperature goal of the Paris Agreement, and instead refer to CO₂ emissions alone. Most of the different decarbonisation roadmaps share the same common features and shortcomings:

• All delay action for another day – it’s easy to say someone else will do something else, sometime in the future;
• Most point to a single hypothetical scenario of what could happen, rather than what will happen as a result of current plans;
• These scenarios often depend on the ‘right’ support in place from governments, with the sector avoiding responsibility for not making progress in their absence;
• They generally rely on techno-fixes, efficiencies and other solutions that have not yet been invented, or proven at scale;
• Sustainable fuel feedstocks and e-kerosene production capacity will be in high demand from multiple sectors, yet the aviation sector assumes it can secure all of the fuel it wants;
• Savings are represented as absolute CO₂ emission reductions, when in fact they are more likely to be avoided CO₂ emissions – which are not the same thing and don’t help achieve net zero;
• Most ignore the GHG emissions budget linked to the Paris Agreement 1.5°C temperature goal, i.e., success isn’t just reaching net zero by 2050 – cumulative emissions between now and 2050 matter more and reductions are necessary now (see figure below);
• All ignore the ethics of inaction; every industry is dealing with decarbonisation challenges and there are plenty of other special cases – including agriculture. Where is the conversation happening between industries about whether to prioritise a tonne of CO₂ for food production, for example, versus a round trip to the other side of the world?
• Neither is there any meaningful discussion on equity-based social change to guide aviation decarbonisation decision-making^[xviii].

Net zero by 2050 doesn´t mean cumulative aviation CO₂ emissions will stay within a 1.5°C GHG emissions budget^[xix]

The decarbonisation roadmaps rarely look back to compare progress on targets against previous forecasts. Perhaps this might raise concerns over credibility, given the sector’s poor track record on delivering against its environmental targets^[xx]. It’s hard to escape the conclusion that these decarbonisation roadmaps are public relations exercises whose purpose is to deflect and defend. Or to put it more charitably, they are opportunities to inform policymakers on the support the sector needs to decarbonise, highlight the excellent progress the sector has made to date and to counter the negative press stoked by NGOs.

Annual reduction target

An alternative approach is possible, indeed necessary. One which better recognises the urgency of the climate crisis and clearly signals the importance of proactively engaging all stakeholders to deliver change in the short term. We propose that the sector adopts, as a minimum level of ambition, the same commitment that other sectors are adopting for 2050 net zero setting, i.e. a linear annual reduction target of 4.2% as set out by SBTi^[xxi]. We note however, that even this minimum approach is inconsistent with achieving the Paris Agreement goal because even greater annual emissions reductions are now required^[xxii] and this is before accounting for the sector’s non-CO₂ warming. As a result, we also propose that the sector immediately start measuring and reporting its full climate impact, i.e. both CO₂ and non-CO₂ emissions. The sector’s CO₂ emissions can be used as a proxy for the net zero pathway, but the focus must shift to align with the Paris Agreement temperature goal in the near term, for example by COP29.

Focusing on timeframes within the tenures of current CEOs and industry leaders would help improve accountability. But it would also allow for fresh thinking on priorities and potential solutions in the short term to mitigate the sector’s climate impacts. This could include, for example, avoidance of persistent warming contrails^[xxiii] and targeted use of sustainable aviation fuel^[xxiv], which potentially offer some of the few reasonably effective and efficient mitigation options (aside from economic instruments) in the near term. These then allow time for scaled up R&D on airframe, engine, fuel and other potential technologies to take effect in the mid-term, in addition to airspace modernisation and other operational measures.

The sector would be free to use its basket of measures in whatever order it wishes, but it must meet the annual reduction target. In the short term it may have to rely on some economic instruments, potentially including demand management, but this will only incentivise the sector further to get into action. The default ‘business as usual’ scenario focusing on growth may otherwise lead to stranded assets of aircraft and airport infrastructure on a scale we are all too familiar with, again impacting aviation workers and investors.

Policymakers should also consider how best to drive this change forward. ICAO brings the ‘common but differentiated responsibility’ conundrum as well as distractions between domestic and international flights, while IATA does not represent the full sector. Perhaps realigning with the main UNFCCC process could help ensure consistency in climate change mitigation policy.

On the corporate side of the aviation sector, we note the increase in climate related shareholder action and litigation. A number of high-profile appeal cases are likely to have established precedent and will influence future case law. Some specific examples include:

• Heathrow Airport’s third runway application was found not to have taken account of the Paris Agreement;
• A greenwashing lawsuit has been filed against KLM in the Netherlands, over misleading marketing that promotes the sustainability of flying^[xxv];
• Shareholders at Delta and United Airlines voted for increased transparency on the company’s climate change lobbying, while shareholders of Air France-KLM have pursued the Board on its environmental commitments;
• Shareholders are increasingly seeking airlines to be more transparent about their GHG emissions performance by disclosing to CDP;
• An institutional investor has forced Spanish airport operator AENA to give shareholders an annual vote on its efforts to tackle climate change; and
• Institutional investors are also monitoring aviation climate related risk disclosures (known as Task force on Climate related Financial Disclosures – TCFD).

New sustainability disclosure requirements, in Europe in particular, are beginning to force the sector from its laggard position to be more transparent about the environmental and social risks it faces and how it plans to respond. The role of sustainable finance is important here too. Parts of the sector have already begun to respond to requests from investors, financial regulators and other stakeholders on climate risk disclosure, for example through CDP, SBTi and TCFD. The TCFD’s transition risks are of special interest as they will likely impact aviation workers most.

The sector needs to be serious about its ESG due diligence, risk assessment and reporting of climate transition plans. We know there are risks facing the sector, and in particular for its workers. Any chance of delivering a just transition requires collaboration and dialogue between aviation industry leaders and employees.

After decades of inaction and missed targets, the aviation sector has a credibility gap and risks being perceived as the next Big-Tobacco / Big Oil, given the similar strategies used by each. The sector has known about and downplayed its climate problem, has sought to distract and delay mitigation at national, regional and international levels. It remains solely focused on near term economic growth with little appetite to consider its externalities, including the pollution and climate impact it is responsible for, or how its employees will fare in the transition to a low carbon economy. Industry leaders understand the challenges in attracting and retaining the best people to help them deliver the change necessary to reduce its climate impact and improve its climate resilience.

Ultimately, the sector’s social licence could come into question, with movement caps at Amsterdam’s Schiphol Airport and domestic flight bans in France just the beginning.

The authors represent Safe Landing, a group of aviation workers campaigning for long-term employment by challenging industry leaders to conform with climate science and reject dangerous growth.

About the authors

Finlay Asher co-founded Safe Landing in 2021. He spent seven years at Rolls-Royce designing future aircraft engine systems and working on various Airbus and Boeing airframe platforms. He worked in System Design on the Trent 7000 (Airbus A330neo), Trent XWB (Airbus A350), UltraFan geared turbofan, and within the Vision 20 future programmes team studying novel propulsion such as Variable Pitch Fan and integrated airframe/engines concepts.

Dr Jarlath Molloy has held roles in a number of organisations connected to the aviation sector and has worked on multiple initiatives and industry groups. He is also a Chartered Physicist.

Top photo: KLM is among a number of companies targeted in a guerrilla poster campaign by Brandalism (© Michelle Tylicki / Brandalism)

Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

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[xxv] Client Earth (2022) Greenwashing lawsuit against KLM airline has been filed in court, available at https://www.clientearth.org/latest/latest-updates/news/we-re-joining-legal-action-against-dutch-airline-klm-for-greenwashing/

Few industries have welcomed the end of Covid-related travel restrictions as much as the global aviation sector. After more than two years of pain, demand is returning, services are ramping up and revenue is flowing again. The recovery has begun, albeit tentatively. But the return to the skies has placed a renewed focus on the industry’s most pressing problem – the reduction of greenhouse gases. As one of the world’s biggest emitters of GHGs, the industry and its regulators have long been trying to address its sustainability issues. In recent years, this has increasingly included the publication of roadmaps to a greener future. These range from Waypoint 2050, by the global industry association ATAG, to the International Energy Agency’s Aviation report and Roland Berger’s Roadmap to True Zero. Some aim to significantly cut carbon levels, while the more ambitious promise a pathway to net zero or even climate neutrality. The question is, how effective are the roadmaps’ decarbonisation levers likely to be? Nikhil Sachdeva of Roland Berger deconstructs the published roadmaps, focusing on the levers they intend to utilise and their potential emissions-reduction impact, and also examines the significant but largely overlooked problem of non-CO₂ GHG emissions.

Global aviation CO₂ emissions plummeted after the outbreak of the coronavirus pandemic in early 2020. Even today, they remain far below Roland Berger’s pre-Covid forecast. Our latest post-Covid forecast shows they are expected to rebound as demand recovers, albeit to a considerably lower level. This is the first time in aviation history that predicted growth in air travel is forecast to become de-linked from a concomitant growth in emissions. This is due to efforts by the sector to decarbonise: investment in new technologies, such as sustainable aviation fuels and hydrogen, are forecast to make it possible.

Source: Roland Berger

However, the assumed effects of radiative forcing from non-CO₂ GHG emissions are even more significant. Like carbon, NO_x, SO₄, soot and contrails absorb energy and contribute to atmospheric warming. These must therefore also be removed if the aviation industry is to not just decarbonise but achieve ‘True Zero’ emissions. Although still poorly understood, with wide error bars and ongoing debate on how best to quantify CO₂ equivalence, the latest research suggests the total radiative forcing impact of non-CO₂ emissions could be three times that of carbon.

Clearly, something needs to be done to address the industry’s emissions problem. The roadmaps, produced by industry groups, regulatory bodies and third parties, have emerged as the basis of potential solutions. They tend to focus almost entirely on decarbonisation, usually citing a continued lack of hard evidence on the reduction of non-CO₂ emissions as the reason for their omission.

Waypoint 2050 (2021): Produced by the Air Transport Action Group, the global commercial aviation sector’s industry association, this roadmap outlines several decarbonisation scenarios that would result in net zero. The three most ambitious lean heavily on SAFs.   

International Civil Aviation Organization Long Term Aspirational Goal report (2022): ICAO, the United Nations’ aviation agency, presents three decarbonisation scenarios (IS1, IS2, IS3), with the most ambitious aiming to cut CO₂ emissions by 87% by 2050 (vs. 2019 levels). It relies mainly on SAFs.

Sustainable Aviation (2020): This is the UK aviation industry’s strategy to achieve net zero by 2050. It is currently focused on market-based measures, specifically the European Union’s Emissions Trading System and ICAO’s Carbon offsetting and reduction scheme for international aviation (CORSIA).   

Destination 2050 (2021): The European aviation industry’s route to net zero is primarily based on improvements in aircraft and engine technologies, especially hydrogen- and electric-powered aircraft. 

Transport & Environment Roadmap To Climate Neutral Aviation (2022): Transport & Environment is a Brussels-based NGO. It promotes zero-emission aircraft as a potential long-term solution, and demand management as the best way to cut emissions in the short term.

International Energy Agency Aviation report (2021): The roadmap of the IEA, a part of the Organisation for Economic Cooperation and Development, places an emphasis on ICAO’s CORSIA scheme and further carbon pricing measures. It has three scenarios, each more ambitious than the next: Stated Policies; Sustainable Development; and Net Zero Emissions.

Roland Berger Roadmap To True Zero (2020): Our roadmap acknowledges that there is no silver bullet to achieving ‘true zero’ emissions, including those from non-CO₂ GHGs. Instead, it offers a five-point plan, the most ambitious of which is investing in new propulsion technologies such as fully electric and hydrogen fuel cell aircraft. In contrast, Roland Berger’s Baseline forecast (2022) is built around evolutionary improvements that have already been announced by industry players, for example the entrance into service of hydrogen aircraft.

In general, the roadmaps agree on the same primary decarbonisation levers: operational and infrastructure improvements; development of aircraft technology (electric, hydrogen powered); uptake of SAF; and the use of market-based measures (offsetting, emissions trading). However, each takes a different view on future technologies, fuels and markets, and applies the levers to different degrees.

But they disagree on which levers, and the extent of decarbonisation, that is achieved. The roadmaps can be split into two categories, based on the effort required to implement them – and indeed the belief systems underlying them. The first are ‘art of the probable’ roadmaps, which present realistic pathways to significantly reduce aviation emissions. These focus on market-based measures and offsetting. The second are ‘art of the possible’ roadmaps. They lay out radical, optimistic strategies that would allow the aviation industry to make a substantial contribution to combating climate change, based largely on SAF and new technologies. This requires a dramatic ramp up of at least one decarbonisation lever.

Source: Roland Berger

As the name suggests, implementation of ‘art of the probable’ roadmaps is realistic as they are based on established or consensus expectations, though they will be challenging nevertheless.  ‘Art of the possible’ roadmaps, meanwhile, are more ambitious and uncertain, relying on the timely and successful development of new technologies. This places them at the very limit of what is possible and means their implementation will be extremely challenging.

So, what are the actual effects of the roadmaps on carbon emissions? In the case of the ‘art of the probable’ category, the roadmaps all lead to a flattening of net CO₂ emissions, typically by around 2040. They forecast emissions ranging from 66% to 160% of 2019-level CO₂ emissions by 2050. This means that in each case, there is a large amount of unmitigated emissions remaining (between 39% and 64% depending on the publication). All of the roadmaps in this category expect that these will have to be addressed through market-based measures and/or offsetting, making them the main decarbonisation lever (with SAF the leading alternative).

Source: Roland Berger

The 2050 forecasts of the ‘art of the possible’ roadmaps are much more optimistic. They range between 0% and 21% of 2019-level CO₂ emissions. The breakdown of emission reduction levers highlights the important role of SAF (ICAO, Waypoint 2050) and aircraft technology improvements (Destination 2050, Roland Berger) in achieving these reductions, as well as the limited need for market-based measures or offsetting.  

Source: Roland Berger

Time will tell which lever proves to be the most successful. Ultimately, commercial viability is likely to play the key role. Regulation and mandates can only carry an industry so far, and technological advancements are neither assured nor guaranteed to be viable in such a highly specialised industry. A combination may well prevail.

No matter what the levers, all emissions-reduction roadmap publishers need to place far more emphasis on the climate effects of non-CO₂ GHGs. These are likely to make a substantial contribution to global warming and the aviation industry ignores them at its peril. If non-CO₂ effects continue to be overlooked, plans to optimise decarbonisation risk worsening their impact.

About the author

Nikhil Sachdeva

Nikhil heads up Roland Berger’s Centre for Aviation Sustainability and is a leading voice in how the aerospace & aviation sectors can achieve climate neutrality.

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Top photo: Airbus

Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

Editor’s note: Nikhil will be making a presentation on roadmaps at the Aviation Carbon 2022 conference in London 17-19 October

The aviation industry faces a conundrum: aviation emissions need to fall now, but the technical solutions to achieve this take time to reach maturity. Andrew Murphy, Aviation Director at Transport & Environment and Board Member of the Climate Change Advisory Council of Ireland, explains what needs to be done now to address aviation’s climate impact. In its new ‘Roadmap to climate neutral aviation’, the clean mobility NGO Transport & Environment shows that a mix of demand management and technology deployment are needed to bring aviation in line with our climate goals. But the key finding is that for the rest of this decade, the only way to reduce emissions from flying substantially is to reduce flying. In time, however, if we step up the deployment of innovative fuels and require manufacturers to sell zero-emission aircraft, demand management recedes as the most effective way to reduce emissions, he writes.

Europe’s efforts to address aviation’s climate impact, as seen in its fuel and carbon pricing proposals launched last year, can be seen as either an historic step towards getting to the root of the problem or as not nearly enough to address aviation’s mammoth climate problem.

The reality is that both of these views are correct. The EU legislation, called the Fit for 55 package, finally gets to the root of the problem: better pricing of aviation emissions and developing alternative fuels to replace fossil kerosene. European co-legislators could bring the package a step forward by also using it to address aviation’s non-CO2 climate effects and supporting the deployment of zero-emission aircraft.

But even with the best will in the world, sustainable fuels will take time to be scaled up. There aren’t enough existing feedstocks for sustainable aviation fuels (SAF) lying around waiting to be used, and a dash for higher targets would result in airlines filling up with unsustainable animal fats, crop biofuels and used cooking oil. Production of the most promising alternative fuels based on renewable electricity, known as e-kerosene, will only scale up towards the end of this decade. And new electric and hydrogen aircraft are exciting prospects but likewise will take time to come to market. Solutions to aviation’s non-CO2 effects are also increasingly viable but also need time to be developed and deployed.

We now face a conundrum. Aviation emissions need to fall now, but the technical solutions to achieve this take time. Thankfully, the Covid crisis has shown that while technology is scaled up, we have ways to immediately reduce the climate impact of flying. What the pandemic showed was that while aviation as a sector was crucial, not every flight ever taken was so. Physical connectivity isn’t always essential to economic growth and employment, and not every corporate deal needs face-to-face meetings.

With this knowledge, Transport & Environment (T&E) has revised its forecasts in its new Roadmap to climate neutral aviation for the mix of demand management and technology deployment needed to bring aviation in line with our climate goals. Our key finding is that for the rest of this decade, the only way to reduce emissions from flying substantially is to reduce flying.

Why do we say this? First point to make is that there are relatively easy ways to reduce emissions through demand management if we target the right flights and fliers. One per cent of the global population is responsible for 50% of emissions from flying and a big share of this, about 30% in Europe, comes from corporate flyers. A golden window exists right now for top corporate executives to decide to align their travel policy with their climate commitments. 

The pandemic has shown a 50% reduction in corporate travel is more than possible. Such a reduction can cut CO2 emissions by as much as 32.6 MtCO2 by 2030, equivalent to taking 16 million polluting cars off the road. We know that the vast bulk of emissions comes from (corporate and leisure) long-haul flights. Substituting long-haul corporate travel by videoconferencing and switching from long-haul to short-haul holiday trips would have serious gains for the climate.

The second point is that demand management isn’t a “forever solution”. It’s the best solution for now, because the sector has dragged its feet in deploying in-sector emission reductions. To many of us working in this area, it seems like airlines spent more money opposing climate measures than supporting new technologies. Much more time was spent pushing offsetting as a solution or believing that the flawed UN aviation agency ICAO would do the job. There are consequences for the failure to deploy the innovation needed to decarbonise the sector.

Our analysis shows that if we step up the deployment of innovative fuels and require manufacturers to sell zero-emission aircraft, then over time, demand management recedes as the most effective way to reduce emissions. However, for that to occur, a fundamental shift from industry is needed. Rather than using their recently adopted net zero pledges as the basis for lobbying for more effective climate measures, many of them are doing the opposite: using them as cover to oppose the very measures that are being proposed to reach such a target. We’ll be exposing more of these anti-climate tactics in the near future.

This sort of short-term thinking is incredibly counter-productive and goes against the optimistic findings of our report: that the technology solutions are actually deployable and can save the industry’s future. Rather than seeing climate measures as a threat, the entire aviation industry should look to them as their best pathway towards an economically and environmentally sustainable future.

That means using their substantial lobbying power to strengthen, not weaken, the proposed legislation. They should provide their technical expertise to help address complex aspects such as non-CO2 effects and provide clearer timelines for deploying zero-emission aircraft. Some in the industry are understanding this already, the others need to follow suit.

We can be optimistic about the possibilities of sustainable aviation, but we shouldn’t be naive about the challenges. Those challenges will be overcome through support for innovators and those providing solutions, not by listening to those who have worked so hard against climate measures. The sooner we do this, the sooner new technologies will overtake flying less as the most effective way to reduce aviation’s emissions.

Photo: EASA

About the author

Andrew Murphy

Andrew joined T&E in 2014 having previously worked for the Green European Foundation and at the European Commission’s transport directorate. Since 2021, he is a member of Ireland’s Climate Change Advisory Council. Andrew leads T&E’s work on sustainable aviation, which includes pricing mechanisms, new fuels and finally addressing aviation’s substantial non-CO2 climate effects.

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Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

The year ahead will be critical for policy to tackle aviation’s contribution to climate change. Following the outcomes of IATA’s annual meeting and COP26 in late 2021, global regulatory co-ordination of international aviation emissions is now firmly in the hands of ICAO. A review of CORSIA by its CAEP environment committee in February and a high-level meeting of ICAO member states in July on a long-term aspirational goal will be followed by the 41st Assembly in late September to formalise conclusions. Chris Lyle describes some key features in the process, notably the heavy reliance in the short- and mid-term on carbon offsetting and the need to turn sustainable aviation fuels into the primary mitigation tool. He looks at the policy challenges and constraints on ICAO alongside the consequential need for complementary action, at least by more ambitious governments.

Trade body IATA has consistently been a driver of ICAO policy and standards, not least on environmental measures. At the Association’s annual general meeting last October a resolution was adopted committing the airline industry as a whole to achieving a goal of net zero carbon emissions by 2050 and aimed at influencing ICAO’s long-term policy on climate change.

On the regulatory front, while the UNFCCC delegated the responsibility of emissions mitigation for international aviation through ICAO in the 1997 Kyoto Protocol, the issue has in the past few years moved into the mainstream. At COP26 in Glasgow, a day was devoted to transport during which the UK government brought together countries under the banner of the International Aviation Climate Ambition Coalition (IACAC) to present a declaration calling for “ambitious actions to reduce aviation CO2 emissions at a rate consistent with efforts to limit the global average temperature increase to 1.5⁰C” and “support the adoption by ICAO of an ambitious long-term aspirational goal consistent with the above-referenced temperature limit, and in view of the industry’s commitments towards net zero CO2 emissions by 2050”.

In addition to the UK, the declaration has 24 further signatories so far – more are being encouraged to join – including 13 European countries and others such as Canada, Japan, New Zealand, Republic of Korea, Turkey and the US, plus some from the developing world, but excluding major players such as Brazil, China, India, Russia and South Africa.

While the IATA text was deemed to represent consensus of all airlines present at the AGM, Chinese airlines, whose government has a generic target of net zero by 2060, expressed reservations – these were glossed over in the context of an industry agreement but may well raise difficulties at the intergovernmental level.

The IATA resolution was backed up by its Fly Net Zero scenario, with intermediate targets leading by 2050 to mitigation contributions of 65% from sustainable aviation fuels (SAF), 13% from new propulsion technology such as hydrogen, 3% from operations and infrastructure, and 19% from carbon offsetting and carbon capture (which could also be used to create more SAF). The IACAC declaration had no intermediate targets and lacked detail or backup.

Both IATA and IACAC strongly endorsed ICAO as the appropriate forum in which to address emissions from international aviation and, for the short- and mid-term, both were strongly supportive of, and heavily dependent on, carbon offsetting (the contribution anticipated by IATA being 93% in 2030 for example) and, in particular, ICAO’s Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).

The IACAC declaration opened the door to actions beyond the ICAO framework through the clause “Working together, both through ICAO and other complementary co-operative initiatives [author’s italics] towards net zero CO2 emissions by 2050”. In this context, concern by IATA regarding a “patchwork of measures” is overhyped. Airlines already deal with a plethora of differing charges and duties in the countries they serve, and the countries themselves, individually or in regional co-operation will ensure that measures they take do not unduly affect competition and become detrimental to their economies.

Drivers of action

In August 2021, the first part of the IPCC’s sixth Assessment Report (AR6), the physical science basis stated that evidence of the human contribution to climate change was now “unequivocal” and stressed the need to limit temperature increases to 1.5°C above pre-industrial levels. In February this year the second part of AR6 will be the latest assessment of the impacts of climate change and in March the third will report on future socio-economic pathways and how they would influence the climate. A synthesis report will be published in September.

These reports will undoubtedly keep concern regarding climate change on the front burner worldwide. As regards the aviation industry, a study published last November by an eminent group of scientists suggests emissions produced must be reduced each year if they are not to increase warming further, otherwise the sector could consume up to one-sixth of the remaining budget to limit warming to 1.5°C by 2050.

The Kyoto Protocol has now effectively lapsed and international aviation is de facto encompassed by the Paris Agreement in the same way as any other sector. While international aviation continues (with international shipping) to be treated separately and specifically, there has been increasing acknowledgement, now confirmed by a legal analysis, that it is to be included in the UNFCCC’s Nationally Determined Contributions (NDCs) under the Paris Agreement.

 The UNFCCC currently has no explicit guidance on the allocation of international aviation emissions amongst Parties, but a number of countries including the UK and, under their collective NDC, all EU Member States will now include the first outbound leg of any international flight by any carrier in their NDCs.

The United States, which published its updated Aviation Climate Action Plan in November, and the EU have taken a lead in integrating aviation into a comprehensive emissions mitigation package. Both strongly endorse ICAO action and CORSIA. The European Commission’s ReFuelEU Aviation proposal would impose a blending mandate on fuel suppliers to include SAF in aviation fuel supplied at EU airports. The obligation would commence from 2025 at 2% SAF, gradually increasing to 63% (incorporating 28% synthetic kerosene) by 2050. Some EU countries have already brought in a mandate and the UK is due to set out proposals this year for its own mandate.

When the EU decided to include intercontinental flights in its Emissions Trading System from 2012, negative reaction from other countries led to suspension of this application, but that covered flights both to and from EU territory. In the context of NDCs, a proposal by the European Commission to apply the ETS to maritime emissions as part of its ‘Fit for 55’ package, including 50% of emissions from voyages which start or end outside of EU territory, seems to have been more acceptable.

The contribution of CORSIA

CORSIA is a complex form of carbon offsetting and is not aimed at the reduction of emissions but rather sets out to achieve a goal of carbon neutral growth, now with a 2019 baseline – at present CORSIA is estimated to cover only 25% of international aviation emissions through its lifetime to 2035. In addition, CORSIA is fragile and, being based on ICAO Assembly Resolutions and implemented through ICAO Standards and Recommended Practices, it will at no point be binding under international law. Countries such as those major players mentioned above in the context of exclusions from the IACAC Declaration are by no means committed to CORSIA.

The ICAO scheme cannot currently therefore be considered as a significant emissions mitigation measure. However, CORSIA is a comprehensively developed mechanism containing crucial elements such as standards on Monitoring, Reporting and Verification. ICAO has also established ‘CORSIA Sustainability Criteria for CORSIA Eligible Fuels’ which could become an important feature in a more general context. Thus there appears to be some consensus that rather than trying to ‘reinvent the wheel’, CORSIA provisions should be reinforced.

One option floated would be to have it apply at some point to all emissions rather than those above 2019 levels However, this would be in direct contradiction of the ICAO action in 2020 actually to change the baseline to compensate for the impact of Covid-19. Another option rumoured to be under consideration by ICAO’s environmental protection committee CAEP, but reportedly facing strong opposition by some fossil fuel providers, would be in-sector offsetting for funding or purchase of certified SAF products.

Nevertheless, the bottom line is that CORSIA is likely to remain substantially inadequate. ICAO’s current basket of emissions mitigation measures for international aviation – technology, operations, CORSIA and SAF – will contribute pro rata much less than any of the first NDCs to which 192 UNFCCC Parties have committed. Climate Action Tracker has concluded these measures, and notably CORSIA, are “critically insufficient” (the worst level) and compatible with a 4°C+ world.

The scientific consensus in the context of the Paris goals is that aviation emissions need to be reduced at least half from 2019 levels by 2030, en route to net zero carbon by 2050. ICAO has been “exploring the feasibility” of a global long-term aspirational goal (LTAG) for mitigation of international aviation emissions for the past eleven years and is finally expected to adopt one at its Assembly Session this year.

Global SAF policy

Electric and hydrogen powered aircraft are now in prototype or on the drawing board, with the potential to reduce air transport emissions substantially in the longer term. But given they will not have a major global market presence until close to mid-century, particularly at the long haul, there is a critical need for early address of other means of reducing aviation’s emissions. As indicated above, the primary emissions reduction contributor in mid-century is expected to be sustainable aviation fuels, notably waste-based fuels and synthetic e-fuels. However, SAF production and take-up are currently negligible, with very high costs (three or more times than fossil jet fuels) and there is an urgent need for stimulative action.

During a side event at COP26, the World Economic Forum launched a ‘Sustainable Aviation Fuel Policy Toolkit’. This guide should help smaller States in particular to develop SAF. However, a number of countries, including for example small islands with high tourism and hence air traffic, are unlikely to have the capacity to produce SAF in adequate quantities – they may well require special treatment in global policy. There will also be a need to address aspects of specifying and verifying SAF consumption given blending into regular kerosene at airport fuel farms or purchase based on ‘book and claim’ (in which the SAF is not physically transported and entered into the specific aircraft of the entity covering the fuel premium but goes into the fuel system at an airport close to the SAF production facility); in such cases the contribution cannot usually be set against specific flights.

A fundamental need going forward is for clarity of definitions used in the aviation sector of ‘carbon neutral’, ‘zero carbon’, ‘zero emissions’ and ‘carbon net zero’. The IATA, IACAC and EU interpretations of carbon net zero for aviation include out-of-sector carbon offsetting or removals. Proponents of hydrogen and electric power claim that they will be zero carbon – however, this relates only to the flights themselves and excludes the manufacturing and distribution process, a factor which needs to be incorporated.

The sector also needs to address the implications of non-CO2 emissions and contrails, with recent research indicating that they contribute substantially to radiative forcing, although they are correlated as of decreasing in importance with CO2 reductions.

On the global policy front, ICAO remains considerably constrained in having to relate the UNFCCC’s principle of ‘Common But Differentiated Responsibilities and Respective Capabilities’ with the ‘equal application’ provisions of the Chicago Convention. Developing a universal commonality for 193 States takes considerable time and effort and has resulted in a lowest common denominator of CORSIA. Furthermore, the UN agency has no regulatory authority over any individual Member.

With ICAO constrained by the Chicago Convention and lacking regulatory authority, it is clear that other complementary initiatives to multilateral sectoral arrangements on aviation emissions reduction, such as CORSIA or the EU ETS, will be critical. Groups of countries or even individual countries should be free to add their own more ambitious action as promoted by the Paris Agreement. Coalitions of the more ambitious may well be more impactful than global application of lowest common denominator.

States should not be constrained, as they have been in the past, from applying such instruments as fossil fuel levies and low-carbon fuel blending mandates. Direct carbon levies are a potential policy vehicle. Tax exemptions for fossil fuels, which discriminate in favour of air transport and against SAF, electric and hydrogen powered aircraft alike, should be removed but with ring-fencing of revenues for alternative fuel and power source development. Such measures fall within the remit of individual governments, beyond ICAO competency.

Potential ICAO Assembly outcomes

ICAO has planned a careful and comprehensive build up to its 41st Assembly Session. In addition to the technical advice from CAEP in February, there will be five regional Global Aviation Dialogues (GLADs) on a LTAG in March/April and a two-day stocktaking immediately prior to the high-level meeting (HLM) to be held, albeit “in principle”, from 20-22 July. A series of GLADS has been held, initially in 2015, aimed at familiarising participants and receiving feedback on proposals for global market-based measures, and in 2021 on a LTAG.

This year’s series (virtual) is aimed at providing more information on a LTAG and, in particular, results of a CAEP analysis on LTAG scenarios with cost impacts. The objective of the HLM, for which arrangements have yet to be finalised, will look at scenarios, options and means of implementation of a LTAG with a view to making recommendations to the governing ICAO Council for consideration in preparation for the Assembly.

The coming Assembly Resolution(s) might include, first and foremost, a commitment to a clearly defined carbon net zero target for international aviation by 2050. If it is to be credible, that long-term goal will require intermediate targets including one for the reduction of international aviation emissions by at least half from 2019 levels by 2030. More frequent intermediate targets could also be set for review every three years at ICAO Assembly Sessions. The policy should evidently include strengthening of the ICAO basket of emissions mitigation measures, notably CORSIA. At the same time, it is likely to encourage evolution of new technologies such as electric and hydrogen powered aircraft.

Even adoption by ICAO of a 2050 carbon net zero target for international aviation is by no means a given. While some 135 countries have now set or are considering a target of reducing their overall emissions to net zero, only about half of these have specified a target year. Of these, major nations such as Brazil, China, Nigeria, Russia, Saudi Arabia and Ukraine are targeting 2060, and India 2070. The number of countries with commitments to net zero 2050 specifically for aviation is far fewer, even if it includes EU Member States, the UK and the US.

As regards SAF, ICAO can offer general guidance if not metrics specific to individual States. A Resolution might provide a clear definition of what is an acceptable SAF (against a criterion such as a 70% or greater reduction in CO2 versus kerosene on a full life cycle basis). It might also include some indicative global figures for quantified proportions of such SAF. And it could offer a roadmap regarding the early development and application of SAF through:

• progressive SAF mandates;
• tax credits for SAF suppliers (both producers and airports);
• levies on aviation fossil fuels, ring-fenced to SAF production and purchase;
• SAF investment guarantees and green financing; and
• prioritisation of applicable alternative fuel production to the aviation sector.

A valuable, if perhaps optimistic, element in a Resolution would be recognition of the inclusion of international aviation into NDCs through adopting the EU and UK lead in acceptance of national authority/control over the emissions from the first outbound leg of all international flights – with no discrimination in favour of airlines with principal place of business or an AOC in the country concerned.

The concept of holding a high-level meeting in preparation for the Assembly is a constructive innovation since it provides full time devotion to a single subject and should deliver the foundation for action by the Assembly. But while substantial progress towards reaching a global agreement will undoubtedly be made, some countries may reserve their final position until they have reviewed the outcome and implications in depth. There is no doubt that relevant Assembly Resolutions will be adopted but States who feel that the policy is inappropriate or too strong may well, as in the past, file reservations against specific aspects, while other countries will be seeking to assure the flexibility for them to take their own additional action.

ICAO should not restrain but rather encourage greater ambition, on the understanding that it should be complementary rather than undermining or conflicting with the ICAO framework. ICAO measures can only be limited and action by coalitions of the more ambitious will be a necessary means of supplementing the ICAO guidance, or perhaps even the primary mitigation measures – with demand management already appearing above the horizon.

Photo: Opening plenary session of ICAO’s 40th Assembly in 2019

About the author

Chris Lyle

Chris is Chief Executive of Canadian-based Air Transport Economics and in 1997, as the Director responsible in the ICAO Secretariat, he facilitated acceptance of the role given to the Organization through the Kyoto Protocol. He can be reached at clyle@airtransporteconomics.ca.

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Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

In April this year, as part of climate measures to reduce carbon emissions, French MPs voted to ban flights on domestic routes that can be travelled by direct train in less than two-and-a-half hours. This had been reduced from a previous recommendation that proposed the limit at four hours, following a French government bailout to Covid-hit Air France. In the UK, and picked up by the national press, environmental pressure group Campaign for Better Transport (CfBT) is now calling on the government to ban domestic flights where the equivalent train journey is under five hours. Calls for bans of domestic flying have become frequent and the general public perception, driven by the constant criticism of environmental NGOs, is that domestic flying is amongst the most climate destructive activities we humans can make. But how bad is it really and when and where do the alternatives come into play, questions Andy Smith, Head of Sustainability Strategy at Scottish regional airline Loganair.

The objective here is not to argue for one mode versus the other, but to understand the true carbon and financial trades of the travel choices consumers and planners face, rather than relying on the very crude national averages used to make sweeping generalisations.

Firstly, what is the scale of the problem being described: the amount of emissions from UK domestic air travel where there is a five-hour equivalent rail journey?

Using OAG data, I found 127 unique UK domestic city pairs currently served by air. Of these only 46 pairs (36%) had a viable rail route given that the majority of UK domestic air services cross water. Of these 46, only 16 routes (13% of the total) met CfBT’s requirement of five hours by rail and some of these only just on occasional services. One of the key claims of rail proponents is that rail has by far the lowest CO2e per passenger km of any form of travel. The government (BEIS) statistics support this claim but do so by taking a blended average of electric and diesel-powered trains.

Given how widely domestic air travel is condemned, most people are surprised to learn that emissions from the rail network are almost double that of all UK domestic air services (3.0 MtCO2e for rail and 1.6 MtCO2e for domestic air) and both of these are dwarfed by the equivalent emissions of road vehicles at 122.6 million tonnes of CO2e per annum. Over half of rail emissions come from diesel trains and although the majority (80%) of rail journeys by kilometre are made by electric train, only 42% of the UK’s rail network is physically electrified.

The electrified network, apart from the East and West Coast mainlines, is concentrated in the commuter belt around London and these commuters account for the majority of UK rail traffic. Outside of the mainlines and the London region, electrification is sparse and patchy and of our 16 “doomed” domestic air routes, only seven can be operated by purely electric train services. Nonetheless, diesel services can connect with electric services to allow efficient travel but this is not necessarily how services are timetabled.

Is there any significant difference between diesel and grid-powered electric train emissions? In short, yes. There are only very opaque figures reported by the rail industry and none on the fuel use per train service or per kilometre travelled by traction type but some high-level figures are available. Taking the regulatory Office of Rail and Road’s 2019 figures of 66.7 billion passenger kms travelled and the 80% electrification figure, we get an estimate of 13.3 billion non-electric train RPKs. Against the 1.7 MtCO2e direct emissions from rail, this gives an estimate of 0.127 kg CO2e per diesel rail passenger km. The equivalent direct CO2e figures quoted by BEIS for domestic air travel are 0.130 kg CO2e per passenger km – so close as to be insignificant.

The other 1.3 MtCO2e from rail is the impact of the electrical consumption of the network and uses the grid carbon intensity average. As the national grid’s renewable power generation increases, so the carbon intensity of electrified rail travel reduces. So far so good. However, the structure of the grid means that when demand peaks, fossil-fuelled production is spun up meet the requirement. Any marginal load on the grid is directly driving fossil fuel consumption and conversely any reduction in demand would directly reduce fossil fuelled emissions.

The point is not to argue that the rail electric system should be disconnected from the grid but rather to indicate that all electrical demand is fundamentally equal and at peak times, regardless of whether a train operating company has contracted only green power, marginal electrical train consumption means marginal generation, which in the UK means fossil fuels being burned – coal or gas.

However, for the sake of this analysis we shall assume that all 16 domestic air routes are replaced by electric trains with virtually no emissions from our hypothetical greened grid.

The routes are:

Aberdeen-Newcastle
Aberdeen-Teesside
Birmingham-Edinburgh
Birmingham-Glasgow
Bournemouth-Liverpool
Bristol-Teesside
Cardiff-Southampton
Edinburgh-London
Exeter-Manchester
Glasgow-London
Humberside-Newcastle
Leeds Bradford-Southampton
London-Manchester
London-Newcastle
London-Teesside
Manchester-Southampton

Using the Eurocontrol small emitters tool and the OAG timetable for October 2021, I estimated the total direct emissions of all carriers on these routes at approximately 112,500 tonnes CO2 per annum. Whilst this sounds like a lot, it is less than 0.1% of annual UK transport emissions, which seems hardly worth the airtime and print space given to CfBT’s proposal.

Over 75% of the emissions from the list of flights above come from just two routes, Edinburgh (EDI) and Glasgow (GLA) to London. Flights are operated into every major London airport – LHR, LCY, LGW, STN and LTN – and clearly serve not just the point-to-point traveller but also connect both EDI and GLA to the primary UK long-haul networks which operate out of LHR and LGW. We shall ignore the importance of such connections and also assume that in the interests of reducing our national emissions, the benefits of travellers being able to day-return via air must also be sacrificed. How would the rail network cope with the additional traffic?

The schedules for EDI provide approximately 3 x E190 and 5 x A320 aircraft on the route per weekday in each direction during peak morning hours. For GLA the equivalent is 2 x E-190s and 5 x A320s, which equates to approximately 1,200 and 1,100 seats in each direction respectively. The Pendolino and IET sets which run on the West (WCML) and East (ECML) Coast rail mainlines respectively seat approximately 550-650 passengers and so two additional sets would be required in each direction on both the WCML and ECML to provide a minimum comparable capacity on the core GLA and EDI services.

Combined with the cancelation of the other services in the list, this is increased to three sets in each direction on both WCML and ECML, for a total of 12 ‘diagrammed’ additional units. In practice, this would require at least 16 additional sets to be acquired with a nine-car IET costing approximately £21.6 million, making a CAPEX of around £345 million ($475m) in rolling stock. But there is no need to purchase the extra train sets because the WCML is currently at capacity, with the May 2020 timetable declaring no viable additional paths possible without impacting punctuality performance, so the addition of six peak hour trains is not an option. The ECML is less constrained but unlikely to be able to provide capacity for more than one or two additional peak time trains for the entire length required. The high-speed HS2 rail line, when it comes online, will relieve some capacity on the London to Birmingham leg of the WCML, but will not provide any capacity north of Birmingham, even if future phases are approved, until the 2030s.

A frequently ignored element of carbon emissions from rail travel is the carbon cost of the 100,000 tonnes of steel and 300,000 tonnes of concrete used annually to maintain the network. This is most striking in HS2, where the carbon cost of the infrastructure on the project is estimated to be between 8 and 14 MtCO2e – nearly 10 times the annual emissions from all domestic air travel in the UK, and this is before a single train has been run between London and Birmingham.

To reiterate, there are undoubtedly carbon savings from electrified rail versus flying specifically. But they may not be the cheapest, quickest or most practical way of decarbonising our national transport system. Even if the rail capacity existed to replace the air services, as CfBT demands, the capital cost of £350 million at a 10% return is generating carbon savings at around £350 per tonne of CO2e. A better discussion would be about how we could improve on this figure.

If we are to make genuine progress in reducing the carbon intensity of our transport network we need less stunts, less deriding the green credentials of competing modes of travel and serious, practical discussions about where and how we can cut emissions from the UK’s public transport network the hardest and the quickest.

Top photo: Airbus/Avanti

Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

In March the Greener by Design Group of the Royal Aeronautical Society, together with the Institute of Atmospheric Physics at the German aerospace research organisation DLR, jointly organised a virtual conference entitled ‘Mitigating the climate impact of non-CO₂ – Aviation’s low-hanging fruit’. The conference provoked a Commentary article in GreenAir in July from Professors Keith Shine and David Lee arguing that “low-hanging fruit may be superficially attractive, but only if that fruit is ripe. It is our contention that in reality, many years’ research is needed to establish whether it is viable. Rather than decreasing aviation’s climate impact, premature implementation of the strategy risks increasing it.”  As joint chair of the conference programme committee, and on behalf of the Greener by Design Contrail Avoidance Group, John Green writes to strongly challenge this contention.  The points made in the Commentary were once valid but take no account of the recent advances presented at the conference, he argues.

The conference was very well received by the delegates. One respondent said it was “Probably the most important aviation conference of the year”. A report on the event is available and there was an accurate follow-up article by GreenAir correspondent Susan van Dyk in April.

It was a significant milestone along the path that began in earnest in 2015 at a Royal Aeronautical Society conference entitled ‘Contrail-cirrus, other non-CO₂ effects and smart flying’ at which Professors Shine and Lee both gave invited papers. At the conclusion of that conference, the broad consensus of the round-table discussion was that the science was by then sufficiently mature to move towards action to reduce persistent contrails.  As a follow-up, Greener by Design invited colleagues from DLR, the UK air navigation service provider NATS and some UK universities to form an informal Contrail Avoidance Group. This development and the conference that prompted it were both covered in a report. Over the past five years the Contrail Avoidance Group has stimulated a body of research that has moved understanding forward appreciably. Much of the new information generated by participants in the Group was presented at the March conference.

The envisaged end point of the path we are following is the worldwide adoption of contrail avoidance by operational measures. We well understand that this is likely to be a long and arduous journey. At the 2015 conference, the final consensus was that the quickest route to this goal is likely to be by adopting a regional approach, with Europe taking the first steps. If appropriate ATM practices are adopted in Europe and can be applied to transatlantic air traffic, and if a reduced climate impact can be convincingly demonstrated, application of the practice in the American continent may well follow; eventually, the rest of the world will join in and ICAO will pass the appropriate regulations. Against this grand vision, the Contrail Avoidance Group has set itself the modest goal of achieving a real-world demonstration of contrail avoidance by ATM in the Shanwick Oceanic Control Area (OCA) of the North Atlantic. That goal is now in sight.

One compelling reason for pursuing contrail reduction is that, as recognised in the Shine-Lee Commentary, the present-day climate impact of contrail cirrus is estimated to be 65-70% greater than that of CO_2. What makes this an economically achievable aim is, as Dr Klaus Gierens pointed out at the 2015 conference, the climate impact of contrail-cirrus varies strongly with atmospheric conditions, time of day and other factors. Because of this large variability, a significant reduction in climate impact can be achieved by avoiding contrails on only a small proportion of flights. Accordingly, in his presentation to the March conference, Gierens described a minimally invasive strategy in which only those contrails with the strongest warming effect are avoided. These ‘Big Hits’, with Effective Radiative Forcing (ERF) in the range 10 to 100 W/m² (ie 2 to 3 orders of magnitude greater than the global ERF of contrail-cirrus currently estimated as 57.4 mW/m²) comprise only 1-2% of all flown distances. They offer a powerful handle for reducing climate impact. The basic concept for avoiding contrails, originally proposed by the late Hermann Mannstein of DLR, is illustrated in Figure 1.

The key fact is that the ice-supersaturated regions (ISSRs) required to form persistent contrails and contrail-cirrus are shallow. Consequently, as shown by Professor Ian Poll at the March conference, the fuel burn penalty of diverting to fly above or below them is very small. It is considerably less than 1% even if the aircraft is flying at the conditions for minimum fuel consumption. The study of contrail avoidance in Japanese airspace, covering all traffic in the defined region over six periods of one month spread over the year, as reported by Stettler et al. at the March conference, brings this home forcefully. 

Figure 2 taken from this study shows 80% of the total energy forcing (EF) by contrails over this period was by 2% of flights, confirming the assessment by Gierens of the frequency of the Big Hits. Stettler at al investigated the effect of an increase or decrease of 2,000ft in cruise altitude for contrail forming flights. They used the DLR CoCiP code to predict the change in total energy forcing, integrating the Global Warming Potential of the change in CO₂ over a time horizon of 100 years. Overall, they found diverting 1.7% of flights reduced contrail-cirrus EF by 59% and total (contrail + CO₂) EF by 36%. The average fuel burn and CO₂ penalty per diverted flight was 0.27% and for the fleet overall it was 0.014%.

These are striking results and, taken together with the other results presented at the March conference, overturn the previously asserted view that contrail avoidance by ATM measures will increase fuel burn, CO₂ emissions and airline costs unacceptably. It is time for the airline industry to recognise this and lend its support to a campaign to implement contrail reduction.

The main obstacle to the successful implementation of a contrail avoidance strategy is the present limitation in the ability of meteorological organisations to predict the location of ISSRs with sufficient accuracy. Improved ISSR prediction was agreed at the March conference to be a priority area for future advance. The study of forecasting accuracy presented by Gierens concluded that present methods are sufficient to predict the region and approximate time period for contrail-cirrus formation but more work is needed. It is a field in which computing power has recently been increased substantially and in which Gierens sees the future need now as an improved representation of the microphysics of ice clouds within their ambient humidity (and supersaturation) field. It is envisaged that this would lead to improved predictions of both cirrus properties and ISSRs. A future GreenAir Commentary is expected by Durant et al. from SATAVIA reporting important advances in ISSR prediction that have recently been made.

The declared aim of the Greener by Design Contrail Avoidance Group is to achieve a successful demonstration of contrail avoidance by tactical use of ATM in the Shanwick OCA. The Aerospace Technology Institute is working to facilitate this, although progress has been delayed by Covid. In addition, as reported at the March conference, DLR and Eurocontrol are jointly engaged in a year-long investigation of tactical contrail avoidance in the crowded airspace of the Maastricht Upper Area Control (MUAC) region of Northern Europe. Both these trials will be significant steps along the road to embedding contrail avoidance as part of ATM procedure in Europe and across the Atlantic, with the eventual roll out of the practice worldwide. As admitted above, this is likely to be a long and arduous road. There will be much work needed to answer all the questions and gain the confidence of the operating and regulating community that the time is ripe to take the next step.

Professors Shine and Lee assert that the time is not ripe. Greener by Design strenuously challenges this. Their Commentary consists of generalised statements and makes no reference to the papers presented at the March conference. Indeed, we might be forgiven for wondering if either of them is aware of the material presented. And we consider it ingenuous to imply that unless their advice is heeded, contrail avoidance will be introduced imminently. There is plainly no possibility of that. Contrary to their view, we see now as time for action – urgent action.

Contrail avoidance has the potential to reduce aviation’s climate impact by at least a half. It can be applied to the entire world fleet, whatever its level of its technology. It is not just the ‘low-hanging fruit’, it is the lowest hanging fruit available to the aviation industry. It will take some time to roll out but could be expected to be effective worldwide many years before the yet-to-be developed new technologies (such as synthetic fuels) have penetrated a significant proportion of the fleet. It is important that policymakers appreciate the potential reduction in climate impact from aviation that can be achieved by contrail avoidance. Supporting a flight demonstration of its practicality is a key first step which should be taken as a matter of urgency.

Top photo: Contrails over the North Sea (credit: European Space Agency)

About the author

Dr John Green (greensinwoburn@gmail.com) spent his early life as an aerodynamicist researching turbulent boundary layers at Cambridge and the then Royal Aircraft Establishment (RAE), becoming successively Head of Subsonic and Supersonic Wind Tunnels, Propulsion and Noise Divisions before becoming Head of Aerodynamics Department. After time in MOD HQ as Director, Project Time and Cost Analysis and in the Embassy in Washington as Deputy Head of British Defence Staff he returned to RAE as Deputy Director Aircraft before resigning from government service to become Chief Executive of the Aircraft Research Association. He was President of the Royal Aeronautical Society in 1996-97 and of the International Council of the Aeronautical Sciences in 1996-98. He has been a member of the Executive Committee of Greener by Design since its formation in 2000, chaired its Technology Sub Group that produced two substantial reports on environmental impact mitigation in 2001 and 2005 and since 2016 has chaired its informal Contrail Avoidance Group.    

Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.