Carbon emissions from international aviation could treble by 2045 and fuel efficiency goal missed, says ICAO

Carbon emissions from international aviation could treble by 2045 and fuel efficiency goal missed, says ICAO | ICAO A40

Thu 25 July 2019 – With an anticipated increase of 3.3 times growth in international air traffic during the period 2015-2045, ICAO projects fuel consumption and carbon emissions will increase by 2.2 to 3.1 times, depending on advances in technology and air traffic management (ATM). International aviation consumed approximately 160 million tonnes (Mt) of fuel in 2015, resulting in CO2 emissions of around 505 Mt. By 2045, if the scenarios were followed, carbon emissions from international flights could rise to between 1,110 Mt and 1,570 Mt. Even under the most optimistic scenario, ICAO’s projected long-term average fuel efficiency improvement of 1.37% per annum falls short of its aspirational goal of 2%. On aircraft noise, the area around airports exposed to yearly average day-night noise levels above 55 dB is likely to remain the same or grow up to 2.2 times during the 2015-2045 period. These global trends, which also include aircraft NOx emission projections, are to help inform environmental discussions at the ICAO 40th Assembly starting in September.


The first ICAO Global Environmental Trends were presented and endorsed at the 37th Assembly in 2010 and have been updated for subsequent Assemblies. “The establishment of the global environmental trends is crucial to the work of ICAO as it provides a robust single reference for sound discussion and decision-making,” says the introduction in a working paper (A40-WP/54) presented by the ICAO Council.


The forecasts are based on a significant modelling and analysis exercise conducted over the past three years since the last 39th Assembly. Despite carbon emissions from international aviation – which make up around 60% of total global aviation emissions – expected to at least double over the long-term, ICAO has now lowered its fuel burn, noise and NOx projections. This, it says, can be attributed to a combination of aircraft with better technology entering the fleet, as well as a reduction in the forecasted long-term traffic demand. The long-term fuel burn is lower by about 25% compared with the projections presented at the last Assembly.


Predicting the contribution of sustainable aviation fuels (SAF) to a long-term emissions reduction comes with “significant uncertainties”, says the paper. A number of near-term scenarios evaluated by an alternative fuels working group within ICAO’s Committee on Aviation Environmental Protection (CAEP) indicate SAF could make up to 2.6% of total fuel consumption by 2025. The analysis suggested that by 2050, it would be physically possible to meet 100% of international aviation jet fuel demand with SAF, corresponding to a 63% reduction in emissions.


“However, this level of fuel production could only be achieved with extremely large capital investments in sustainable aviation fuel production infrastructure, and substantial policy support,” says the paper. “The effort required to reach these production volumes would have to significantly exceed historical precedent for other fuels, such as ethanol and biodiesel for road transportation.”


The paper notes that CAEP did not consider the contribution of ‘lower carbon’ aviation fuels in its trends analysis, which will be covered as part of CAEP’s work programme over the next triennium.


The long-term 1.37% annual fuel efficiency improvement is made up of 0.98% from technology and 0.39% from operations.


In 2015, full-flight emissions of nitrogen oxides (NOx) were 2.50 Mt, which is projected to rise to between 5.53 to 8.16 Mt by 2045, representing a 2.2 to 3.3 times growth. As with fuel burn, the long-term forecast has been lowered by about 21% compared with prior projections due to aircraft with lower NOx engines entering the fleet, as well as the reduction in long-term traffic demand. In 2015, NOx emissions within the landing and take-off (LTO) cycle, which affect local air quality, were approximately 0.18 Mt and by 2045 are projected to range from 0.44 to 0.80 Mt depending on the technology and ATM scenario.


For its trends in aircraft noise, CAEP looked at 315 airports representing around 80% of global traffic and the total area exposed to yearly average day-night noise levels (DNL) above 55 dB. In 2015, this total area was 14,400 square-kilometres and the total population inside this area was around 30 million people. The paper notes that under an advanced aircraft technology scenario, from about 2030 the total yearly average DNL may no longer increase with an increase in air traffic. However, it points out, “a number of ambitious actions would need to be carried out on the part of Member States for that scenario to be realised.”


The long-term total DNL 55 dB contour area is lower by about 10% compared with previous projections due to quieter aircraft entering the fleet and a reduction in forecasted long-term traffic demand.


In another working paper (A40-WP/55) to be discussed at the Assembly, ICAO says it has initiated work on the feasibility of a long-term global aspirational goal for international aviation emissions. This was in response to a resolution (A39-2, para 9) adopted at the previous Assembly in 2016, which requested the Council “to continue to explore the feasibility of a long-term global aspirational 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, for the progress of the work to be presented to the 40th Session of the ICAO Assembly. Assessment of long-term goals should include information from Member States on their experiences working towards the medium-term goal.”


A40-WP/55 merely states that work on this will continue for presentation at the next Assembly in 2022.


The aviation industry agreed a long-term target 10 years ago to reduce net emissions by 50% by 2050 based on 2005 levels but ICAO States have so far declined to follow suit. Wording in a draft environmental protection resolution to be considered for adoption at this year’s Assembly (A40-WP/59) states that work related to ICAO’s CORSIA carbon offsetting scheme – designed to maintain 2020 emissions levels – and its implementation “will contribute to the achievement of the goals set out in the Paris Agreement.”




Projected net CO2 emissions from international aviation 2005-2050, including SAF life cycle CO2 emissions reductions (source: ICAO):









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