ICAO technical body issues major analysis on feasibility of a global aviation emissions reduction goal

Annual residual CO2 emissions from international aviation – those emissions that remain after in-sector reduction efforts – could range from 200 million tonnes (Mt) to 900 Mt by 2050, according to a major study by ICAO’s Committee on Aviation Environmental Protection (CAEP). The completed report provides the results of two years of technical work by 280 experts from around the world to explore the feasibility of a long-term global aspirational goal (LTAG) for international civil aviation CO2 emission reductions. Described as the most comprehensive and complex study of its kind, the analysis provides long-term trends and emissions reduction opportunities from operations, new aircraft technologies and future fuels and energy sources against a backdrop of traffic demand forecast scenarios and the climate science. The results show a heavy reliance on sustainable fuels for the most optimistic outcome on in-sector reductions. A decision on whether to adopt a long-term emissions reduction goal is expected to be taken at ICAO’s next triennial Assembly that starts in late September.

The report was adopted “unanimously” at the CAEP/12 meeting in February, according to CAEP Chairperson Urs Ziegler. Its main findings have been presented in an informal online briefing to State members of ICAO’s governing Council. In moves to become a more open and transparent organisation, the briefing, which included initial reactions and questions from Council members about the findings, has been made available publicly on ICAO TV.

ICAO adopted a resolution at its 37th Assembly in 2010 requesting the Council to explore the feasibility of a long-term goal for international aviation “through conducting detailed studies assessing the attainability and impacts of any goals proposed, including the impact on growth as well as costs in all countries, especially developing countries …”. In each subsequent Assembly climate resolution, the Council has been requested to continue the work on the goal’s feasibility.

Briefing Council members on the new report, Ziegler said: “I would like to underline that CAEP stands unanimously behind it and it is important CAEP noted no further work was needed in this area as it would not bring any fundamentally new insights or results that would go beyond what has already been evaluated. There are many other reports out there but none has gone as deep as our experts have done in the last two years. Everything we have proposed in this report is both feasible and attainable.”

A feature of the CAEP studies is that its forecast scenarios on air traffic and fleet evolution have been extended beyond 2050 to 2070. The results have been calibrated against the IPCC’s AR6 scientific report last year on the allowed global CO2 emissions for limiting the global mean temperature increase to 1.5°C or 2°C.

The CAEP LTAG Task Group developed a methodology involving three integrated scenarios – IS1, IS2 and IS3 – to represent a low, mid and high degree of aspiration related to readiness and attainability against a baseline (IS0). The least ambitious scenario (IS1) shows residual emissions of around 950 MtCO2 in 2050 (around 160% of 2019 CO2 emissions} from international aviation, after a total reduction of 39% in 2050 against the baseline as a result of in-sector incremental improvements in technologies (-20%) and operations (-4%), plus new fuels (-15%). The mid ‘increased/further ambition’ scenario (IS2) shows around 495 MtCO2 in residual emissions in 2050 (80% of 2019 CO2 emissions), with a 68% reduction in 2050 emissions from the baseline through technologies (-21%), operations (-6%) and fuels (-41%). The ‘aggressive/speculative’ (high) scenario (IS3) forecasts residual emissions of around 200 MtCO2 in 2050 (35% of 2019 CO2 emissions), with an 87% reduction in 2050 from the baseline through technologies (-21%), operations (-11%) and fuels (-55%).

The three scenarios therefore show the potential for CO2 reductions from in-sector emissions is substantial, although none reach zero emissions, even up to 2070, pointed out Ziegler. Even with a 100% replacement of conventional jet fuel with novel fuels, there are life-cycle emission considerations. However, drop-in advanced fuels are expected to have the largest impact in driving overall reductions by 2050. The analysis shows hydrogen is not expected to make a significant contribution to overall emissions reductions before 2050, largely because hydrogen power was considered appropriate to short-haul operations whereas the bulk of international aviation emissions (ICAO is not responsible for domestic aviation emissions) were from long-haul flights, but may increase afterwards if technically feasible and commercially viable, says the report.

The analysis shows advanced tube and wing aircraft have a clear potential to improve the fuel efficiency of the international aviation system, with an incremental contribution from aircraft with unconventional configurations. The emissions reductions from technology are expected to grow after 2050 as these aircraft penetrate the fleet.

CO2 emissions in 2050 after in-sector emissions reductions from technologies, operations and fuels were modelled against low, medium and high international aviation traffic forecasts. For IS1, CO2 emissions in 2050 are estimated to range from 730 MtCO2 to 1160 MtCO2; for IS2 the range is 420 MtCO2 to 590 MtCO2; and for IS3 the range is 150 MtCO2 to 260 MtCO2. The IS3 scenario demonstrates the critical importance of the contribution from novel fuels to decouple the growth in traffic from its CO2 emissions, says the report.

The costs of LTAG

Using a cost minus baseline approach, CAEP assessed the cumulative costs and investments associated with the integrated scenarios for the period 2020 to 2050. Costs and savings were assessed from technology, operations and fuels measures across stakeholders. Investments required from States in R&D to support aircraft technology developments could be as high as $870 billion in the IS2 and IS3 scenarios, with OEMs adding a further $350 billion. Investments from fuel suppliers were estimated to total $1.3 trillion (IS1) to $3.2 trillion (IS3) across the 30-year period. Costs and investments for ANSPs were estimated at $11-20 billion and for airports $2-6 billion across LTAG scenarios towards the implementation of operations measures. Under the IS3 scenario, a further $100-150 billion would be required towards investments in infrastructure at airports for hydrogen aircraft.

Airlines should benefit, found the analysis, from $710-740 billion in reduced operating fuel costs as a result of aircraft technology improvements, subject to a requirement for incremental fleet investments. A further $210-490 billion could be saved in reduced operating fuel costs from operational measures associated with $40-155 billion of implementation costs. Overall incremental fuel related costs (minimum selling price of novel fuels minus conventional jet fuel price) for airlines against the three integrated scenarios are estimated at $1.1 trillion (IS1), $2.7 trillion (IS2) and $4 trillion (IS3) cumulatively over the period.

CAEP acknowledges LTAG may result in some increases in operating costs being passed on to passengers. There may also be significant regional variations in the production and uptake of fuels due, for example, to regional availability of renewable energy and feedstocks, it adds.

CAEP was not tasked with consideration of the goal itself or out-of-sector emissions reductions, such as from market-based measures, but did look at the potential technical aspects of LTAG implementation, without prejudging future decisions on the goal. It suggests State Action Plans may be used for States to report progress towards a goal and if a goal was adopted, it could conduct future work, for example on possible metrics and reporting mechanisms. ICAO may need to review any goal to ensure it remains appropriate, it says, with perhaps a triennial review process similar to that for CORSIA. It also highlights a possible need for State capacity building and assistance that could include workshops, assistance on monitoring and measuring CO2 emissions and an overarching training programme like ACT-CORSIA.

Backed by other Council members during a Q&A session after the briefing, ICAO Council President Salvatore Sciacchitano congratulated CAEP on its “incredible” work and described the report as “impressive”, adding it would help to better inform the Council in its understanding. Ziegler recommended the full report, said to run to around 500 pages, be made available publicly, which Sciacchitano said would be a decision for the Council.

Some Council members said the report should be published as soon as possible and believed the findings had demonstrated the feasibility of a long-term goal. Other members expressed concerns over the potential costs of a LTAG and feared this would fall disproportionately on developing States and impact aviation growth in those countries.

Jane Hupe, ICAO’s head of environment, told the briefing that all States had approved the temperature goals of the Paris Agreement and they applied not just to individual States but also to all sectors, including aviation. “We have to comply and are required to have more ambitious goals,” she said, adding that there were already signs of a bottom-up reaction by governments and regions on policy decisions, which ICAO had to respond to at a global level. She said a LTAG would require looking again at the ambition of ICAO’s CORSIA offsetting scheme, which is designed to run until 2035 with a carbon-neutral growth goal.

A decision on LTAG will be taken at the 41st Assembly, which has now been extended to run over three weeks, rather than the normal two. It will now take place as a hybrid event between September 27 and October 14.

Before the Assembly, a special high-level meeting (HLM) of State representatives has been convened on the feasibility of a LTAG between July 20 and July 22, intended to be held in-person in Montreal and also online, subject to the Covid situation. It is expected to be immediately preceded by a two-day stocktaking event to share with delegates the latest relevant information. A Small ad-hoc Group comprising 13 Council representatives has been established that will play an important role in facilitating the drafting of a proposal for the HLM.

As a precursor to the HLM, ICAO is also holding a series of five regional virtual events for Member States starting on March 28 as part of the LTAG consultative process. Called the LTAG Global Aviation Dialogues (LTAG-GLADS), they aim to raise awareness of ICAO’s LTAG work and facilitate an exchange of views, in particular on reaching a decision on LTAG.

Update March 22: The report is now available to download at https://www.icao.int/environmental-protection/LTAG/Pages/LTAGreport.aspx

Photo: ICAO Council Chamber