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.

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 1997, the UNFCCC’s COP3 decided, via the Kyoto Protocol, to treat international aviation indirectly through ICAO. CO2 emissions from international aviation have since doubled from 317Mt in 1997 to 641Mt in 2019, to match the total emissions of the 129 lowest emitting countries combined, ranking just behind Canada and at least one and half times those of the UK. Climate Action Tracker, which has been assessing the Nationally Determined Contributions (NDCs) of individual countries under the Paris Agreement, last year turned its attention to international aviation emissions. It concluded that current measures, and notably ICAO’s CORSIA carbon offsetting scheme, were “critically insufficient” – the worst level – and compatible with a 4°C+ world. Therefore, suggests Chris Lyle, that with the opportunity of the Covid-induced delay in the effectiveness of CORSIA and the upcoming COP26, it is time to revisit the ICAO/UNFCCC relationship.

It is currently unclear when international air traffic will return to pre-Covid 2019 levels and whether subsequent growth rates will be lower than in the past, but it remains a likely scenario that without markedly more effective climate policies, damaging emissions from air transport will at least double 2019 levels by 2050. If aviation is to make its requisite contribution to the Paris Agreement targets, its CO2 emissions would have to be reduced by 2030 to half 2019 levels and by 2050 to zero (not ‘net’ zero, which includes out-of-sector carbon offsetting, capture and storage).

The time is overdue to step back from the operational detail of aviation emissions mitigation, to review the effectiveness of current global governance and look to the future.

Technology and operations are a raison d’etre of ICAO and were the initial focus in addressing aviation emissions, including the adoption of standards on CO2 and non-particulate matter for aircraft, and improved air traffic management.

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. ICAO will undoubtedly continue to play a vital role regarding the certification and safety of these new aircraft concepts. But given they will not have a substantial global market presence until close to mid-century, there is a critical need for early address of other means of reducing aviation’s emissions, notably market-based measures and sustainable aviation fuels (SAF).

Voluntary carbon offset schemes from airlines and third parties have been on offer to passengers and shippers for many years but they are minimally taken up. A few airlines currently offset all their emissions themselves.

But carbon offsetting is at best an interim and inadequate mechanism. It shifts the moral responsibility for carbon reduction to someone else, the quality of offset units is heterogeneous and far from guaranteed, and an EU study showed that the majority of even offsets of the highest standards simply do not work. In the words of Christiana Figueres, past Executive Secretary of the UNFCCC: “Carbon offsetting is not a silver bullet, nor an alternative to the deep and decisive emission reductions that economies and communities have to make now and into the future.”

CORSIA limitations

Nevertheless, when technological and operational measures, while effective, proved to be inadequate against a growth in traffic, ICAO turned to carbon offsetting as its primary emissions mitigation measure. This is perhaps understandable given the benefit of hindsight and knowledge of the process of attempting to relate the UNFCCC’s principle of Common But Differentiated Responsibilities (CBDR) with “equal application” provisions of the Chicago Convention, along with the undue influence of the air transport industry. CORSIA is a complex form of offsetting and not aimed at reduction of emissions but rather sets out to achieve a goal of carbon neutral growth. It has been forecast to cover only 25% of international aviation CO2 emissions over its 2021 to 2035 lifetime. CORSIA has also stifled coverage of the EU’s Emissions Trading System, which has a more reliable effect but has been severely constrained in its geographic application to air transport.

Furthermore, 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 – a reason why ICAO has carefully avoided use of the word “mandatory” for the full effectiveness of the scheme from 2027. China, India, Russia and South Africa amongst others are by no means committed to CORSIA.

The scheme cannot currently be considered as a significant emissions mitigation measure. On the contrary, out-of-sector carbon offsetting needs to be discouraged in favour of real in-sector reductions in emissions. While CORSIA may well continue to play a role, it should not by any means be the only global basis for aviation emissions mitigation. However, in-sector offsetting could play a part, for example in funding of SAF.

Pending the arrival of electric and hydrogen powered aircraft there is increasing emphasis, including by ICAO, on SAF. There is no prevalent definition of an acceptable SAF, which may vary significantly from country to country according to the feedstock, and SAF is frequently equated with biofuels. However, many biofuels are not a solution when assessed on a full life-cycle basis, including land use, and on emissions reduction over kerosene. A current exception is biofuels from various forms of waste, which however will face increasing limitations of scale.

More promising are synthetic e-fuels which, like biofuels, have drop-in capability for all contemporary jet aircraft types. The current production of e-fuels is negligible, they require a large amount of green power to produce the liquid fuel, and their present cost is at least three times as high as that of conventional jet fuel.

Biofuels from waste and particularly e-fuels could nevertheless become viable alternatives given the application of blending legislation (for example States designing progressive and legally-binding blending mandates for fuel suppliers, airports and/or air carriers with principal place of business in their territories). But surely issues such as life-cycle and land use, or blending mandates in individual countries, should not be in the remit of ICAO?

Clearly, given the required investments and increased operating costs of SAF and e-fuels, government intervention and support will be necessary. Blending mandates will in any event include small proportions of SAF initially with only gradual increases because of lack of availability and so temper the rise in operating costs.

Direct carbon levies are another 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.

But again, such measures fall within the remit of individual governments, not ICAO provisions.

Long-term goal

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 191 UNFCCC Parties have already committed. Six countries have already submitted enhanced NDCS and a further 120 have advised that they will be doing so before COP26. More than 125 nations, along with some major airlines, have now committed to net-zero emissions by 2050.

But, more than 23 years after being given its Kyoto mandate, ICAO still has no long-term global aspirational goal for mitigation of international aviation emissions, although for the past ten years it has been “exploring the feasibility” of one.

Apart from ICAO’s understandable snail’s pace in trying to get a common approach amongst 193 States prescribed by the equality of application provisions of the Chicago Convention, the UN agency has no regulatory authority over any individual Member. At the outset of its consideration of market-based measures, the organisation dismissed the idea of developing a new legal instrument for aviation emissions mitigation as too cumbersome and taking too long to deliver (a number of years). But in a speech on ‘The State of the Planet’ last December, the UN Secretary General saw a need for enforceable regulatory and fiscal steps in order that the aviation and shipping industries can deliver commitments to net zero.

Much of the above suggests a need for a rethink of the ICAO mandate from the UNFCCC. 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.

Any country can add international aviation to its carbon budget at its discretion and a number of countries are now including it in their NDCs. The UNFCCC at its COP26 in November could incentivise action on aviation emissions by mandating this approach. Several options for allocation of international aviation to Parties were on the table in Kyoto in 1997 before the conference ran out of time, and requisite data have since become much more readily available.

Bringing international aviation into the NDCs would give direct accountability and incentive for States to act on the related emissions, individually or through multilateral mechanisms such as CORSIA and the EU ETS. It would place international aviation more squarely in each national emissions context. Not only can it be difficult to separate domestic from international air transport operations, the two can share broader emissions generation aspects. For example, Heathrow Airport is the largest single source of CO2 emissions in the UK, but the majority of those emissions are from local traffic and business, not from the flights themselves.

COP26 might also provide direction on not only allowing but encouraging greater ambition by individual Parties, complementary but in addition to multilateral sectoral arrangements on aviation emissions reduction such as CORSIA or the EU ETS (on the basis of ‘bottom up’ rather than the current ‘top down’ of ICAO), and empowering individual Parties to apply such instruments as fossil fuel levies and low-carbon fuel blending mandates. ICAO should certainly no longer be sanctioned to continue as the sole regulatory policy framer for international aviation emissions – individual countries should be free to add their own more ambitious action.

Amongst other reasons for bringing policy into the UNFCCC:

• Choice of emission mitigation measures would be at the discretion of individual governments in reflection of their particular circumstances, taking into account the relationship between air transport and their other industries.
• Similarly, the influence of the air transport sector would be taken in a general national economic and emissions context rather than a predominantly sectoral one.
• Governments would be held directly accountable for reducing both international and domestic aviation emissions and each country would be in a position to create incentives for, or impose sanctions on, air carriers, as necessary under its sovereign jurisdiction.
• The generic CBDR principle as agreed to in Paris would apply, removing the discord with the uniform application provisions of the Chicago Convention.
• Overlap, inconsistency and institutional duplication between ICAO’s Emissions Unit Criteria and the UNFCCC’s carbon-offsetting provisions would be avoided, with reduction of concerns regarding the double-counting of offsets.

The time has come also to move beyond the CO2 focus for aviation to take account of the other greenhouse gas and contrail-induced cirrus impacts. Recent climate research has shown that non-CO2 impacts of aviation are significantly larger than those of CO2 alone but they have yet to be included in mitigation measures.

None of the above is intended to be detrimental to ICAO’s fundamental role in aviation safety, security and air navigation and its very impressive work on raising the profile of the need for action on aviation emissions mitigation, development of environmental standards for aircraft certification and the monitoring, reporting and verification (MRV) of fuel consumption and emissions. These activities will continue to be fundamental. But responsibility for global climate policy on international aviation, and criteria for determining the overall contribution of its emissions to climate change, should revert from ICAO directly to the UNFCCC. The present arrangements are entrenched and changes would take time, but there should be critical debate in the build up to COP26.

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.

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