International Aviation

Despite agreeing on ‘carbon neutral growth’ from 2020 and a ‘long-term aspirational goal of net zero carbon emissions by 2050’, the International Civil Aviation Organization (ICAO) and national governments are not taking appropriate action to reduce emissions from international aviation. The sector remains far off track from a 1.5ºC-aligned pathway and is rated as ‘Critically insufficient’.

The International Civil Aviation Organization (ICAO), the UN agency responsible for regulating international aviation, adopted the aspirational goal of ‘carbon neutral growth from 2020’ in 2013. This means net CO₂ emissions after 2020 would have to remain constant compared to 2020. The CAT rates the ICAO goal of carbon neutral growth from 2020 levels as ‘Highly insufficient’. Significant shortcomings of this goal are that it is based on offsetting the sector’s CO₂ emissions rather than real emission reductions, and that non-CO₂ climate impacts are not addressed.

ICAO expects its offsetting scheme, CORSIA, to play a key role in achieving ‘carbon neutral growth from 2020’. However, CORSIA’s eligibility criteria for offsets are weak and inconsistently applied. Carbon dioxide emissions from the aviation sector account for only a third of the overall climate impact of aviation. Indirect greenhouse gases—notably nitrous oxide (NOx) and the climate impact of contrail formation and contrail cirrus—have a combined warming effect that is greater than the direct CO₂ warming effect. Efforts to reduce the climate impact from international aviation must consider the full scope of aviation’s climate effects and must therefore include measures to reduce NOx emissions and minimise contrail cirrus formation.

ICAO and its member states agreed on a ‘long term aspirational goal of net zero carbon emissions by 2050.’ However, ICAO’s plan for achieving this target is unsubstantiated. It is unclear to what extent “net zero carbon emissions” will be achieved through deep reductions—for instance, via demand management, operational measures, or technological improvement. This ambiguity leaves the door open for the use of contentious out-of-sector offsetting.

The lack of interim targets means there is no clear signal for deep decarbonisation in the short or medium term. Similar to the post-2020 target, ICAO’s 2050 target covers only CO₂ emissions, which account for just one-third of aviation’s estimated climate impact. To align the sector with the Paris Agreement’s 1.5°C temperature goals, the international aviation industry needs to reduce CO₂ emissions by 90% below 2019 levels by 2050 (70 MtCO₂), while making deep cuts to non-CO₂ emissions.

Ahead of the 41st meeting of the ICAO Assembly in October 2022, ICAO’s Committee on Aviation Environmental Protection (CAEP) developed three scenarios to inform discussions on the long-term goal. However, these scenarios lead to CO₂ emission levels in a range of 70% below 2019 levels to 50% above those levels (200–950 MtCO₂) by 2050; a range that is well above the Paris Agreement-compatible level. The scenarios also do not address aviation’s non-CO₂ emissions and climate impacts. The CAT would rate a target within the three scenarios’ range as ‘2˚C compatible’ at best and ‘Critically insufficient’ at worst, consistent with at least 2˚C of warming, if not more than 4˚C.

The key industry body, the International Air Transport Association (IATA), has committed to net zero carbon from aviation by 2050. This target relies on offsetting for approximately 20% of reductions and, like ICAO’s targets, does not address non-CO₂ emissions. The CAT would evaluate this target as ‘Insufficient’ at best and ‘Highly insufficient’ at worst.

Prior to the outbreak of the COVID-19 pandemic, international aviation emitted about 600 MtCO₂ per year, or 1.2% of global GHG emissions. After a dip in emissions over the following years during COVID-19, the sector is expected to reach, or even exceed, 2019 levels in 2024. Based on ICAO’s projections, we estimate that without strong action, emissions from international aviation will double or even triple between 2019 and 2050 and reach 1,300-1,800 MtCO₂ by 2050.

In the absence of meaningful action by ICAO, some countries have started to address international aviation emissions themselves. However, few of the proposed strategies aim to reduce the growth of demand for aviation, which is projected to grow exponentially. Most of the strategies rely on carbon offsets, which will not neutralise the climate effects of CO₂ emissions, due to offsets’ lack of permanence and fundamental concerns about additionality. Rather than accommodating the stark projected growth in aviation activity, the limited global potential for carbon dioxide removal and storage should be used to balance out residual emissions and achieve global net zero by 2050.

Just four jurisdictions are responsible for a quarter of international aviation emissions. In order of magnitude, they are the European Union, the United States, China, and the United Kingdom.

The European Union’s nationally determined contribution (NDC) for 2030 includes international aviation, but its climate neutrality target does not explicitly cover emissions from international aviation. Despite calls for including all outgoing flights in the EU emissions trading system (EU ETS) during the EU ETS reforms in 2021-2022, the EU ETS’ scope remains limited to flights within the European Economic Area (EEA) and flights from the EEA to the UK and Switzerland. However, the revised EU ETS Directive provides that free allowances for aircraft operators will be phased out. The revised EU ETS Directive also introduces a requirement for aircraft operators to report on the non-CO₂ effects from aviation, starting in 2025.

The United Kingdom includes emissions from outgoing (international) flights in its sixth carbon budget and will extend its 2050 net zero target to cover emissions from international bunkers (aviation and shipping), which are both positive developments. However, the previous government’s July 2022 Jet Zero strategy to bring domestic and international aviation emissions to net zero by 2050 is unambitious and insufficient. The strategy shows that the UK government understands ‘net zero aviation’ to mean increasing real CO₂ emissions from 19 MtCO₂ in 2019 to 33 MtCO₂ in 2050 and reaching net zero through accounting with the UK ETS, CORSIA and other offsetting measures.

The United States has committed to net zero GHG emissions from the US aviation sector by 2050. This goal encompasses both the emissions from domestic aviation and the emissions from all flights from US operators between two different countries, but not flights from foreign airlines departing from or arriving in the US. The US government proposed measures to reduce emissions from aviation, including sustainable aviation fuels (SAF), but with a strong focus on domestic flights. The government recognises that offsetting may be needed to bring the aviation sector to net zero but provides no further details on the potential scale of offsetting’s role.

To the best of our knowledge, China has not set any targets for the reduction of international aviation’s climate impact.

The CAT recommend that countries, in particular those in the Global North, start including emissions from international aviation in their NDCs and net-zero targets. The Paris Agreement requires developed countries to “undertake economy-wide absolute emission reduction targets”, which we understand to include international aviation emissions.

Governments should pursue a range of measures to decarbonise the aviation sector, including:

• Scaling up the use of SAF to 10-15% in 2030 and 100% in 2050;
• Investing in research and development of other decarbonisation options, such as electric batteries for small aircrafts;
• Implementing operational measures, such as optimising routing, air traffic flow management, and minimising flight distances;
• Improving energy efficiency of aircrafts; and
• Reducing demand for international aviation.

While governments, ICAO, and industry focus on the first four measures, albeit to varying degrees, reducing demand receives very little attention. However, it is unlikely that the aviation sector can move towards a 1.5º-compatible trajectory without reducing demand.