Climate Change: International Policy and Regulation

As an International Civil Aviation Organisation (ICAO) Member State, the UK has agreed to collaborate with other members to improve the level of environmental protection across many areas, one of which is climate change. ICAO is the United Nations (UN) body responsible for tackling international aviation’s contribution to climate change through setting goals, standards and guidance.

Volume III of Annex 16 to the Convention on International Civil Aviation  

As the first global technology standard for CO₂ emissions for any sector, Volume III of Annex 16 to the Convention on International Civil Aviation was published with the aim of encouraging more fuel-efficient technologies in aeroplane design.

The CO₂ standard applies to subsonic jet and turboprop aeroplanes over 5,700 kg and 8,618 kg respectively that are new type designs from 2020. In addition, the CO₂ standard also applies to in-production aeroplanes from 2023 that are modified and meet specific change criteria, with a production cut-off in 2028. This means that any aircraft produced after 2028 must be built to a modified design that meets the CO₂ standard. 

The CO₂ standard is based on fuel burn performance during the cruise phase of flight. To make the evaluation of fuel burn performance most relevant to day-to-day operations, three measurement points representing the gross mass of the aeroplane are used; high, medium and low, which are calculated as a function of maximum take-off mass. This is then applied to a metric which represents the distance travelled per unit of fuel, adjusted to represent the aeroplane size.

This CO₂ standard increases the importance of fuel efficiency in the design process of an aeroplane type and positively impacts upon the industry’s contribution to climate change. In the UK, the CAA is responsible for ensuring compliance against the CO₂ standard during the type-certification and airworthiness processes under UK Regulation (EU) No 748/2012.

Volume IV of Annex 16 to the Convention on International Civil Aviation  

Volume IV of Annex 16 – Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) is a set of Standards and Recommended Practices (SARPs) that, alongside extensive guidance material, form the ‘CORSIA Package', a suite of ICAO documentation that requires and facilitates compliance with CORSIA. CORSIA is the world’s first global market-based measure to address CO₂ emissions from any single sector. CORSIA was adopted into ICAO Assembly Resolution in 2016 and into Annex 16 in 2018. Monitoring and reporting of emissions under the scheme began in 2019. CORSIA's first phase, and the start of offsetting requirements, began on 1 January 2024 with 126 participating States. From 1 January 2025, three additional States (Comoros, Mauritania, and Saint Lucia) joined, bringing the total to 129.

Chapters 1 and 2 of Volume IV contain provisions for monitoring, reporting and verifying aeroplane operator CO₂ emissions from international flights. These are implemented into UK legislation through The Air Navigation (Carbon Offsetting and Reduction Scheme for International Aviation) Order 2021 (UK Statutory Instrument 2021 No. 543).

Chapters 3 and 4 of Volume IV contain provisions for applying, calculating and meeting offsetting requirements under CORSIA. This includes which emissions units (offset credits) can be used and how offsetting requirements can be reduced through the use of CORSIA Eligible Fuels.

Long-term Global Aspirational Goal 

At the 41st ICAO Assembly in 2022, ICAO Member States adopted a long-term global aspirational goal (LTAG) for international aviation to reach net zero carbon emissions by 2050. Adoption of the goal was underpinned by work carried out by CAEP, which set out three scenarios for emission reductions based on technology, operations, and fuels. The scenarios range from ‘high readiness/attainability and low aspiration’ to ‘low readiness/attainability and high aspiration’. Scenarios were analysed to understand the impacts on CO₂ emissions, costs and investments, and considered implications for aviation growth, noise, and air quality. According to the scenarios, possible CO₂ emissions reductions for 2050 could be between 39% to 87% compared to a ‘frozen technology’ scenario, with a contribution from sustainable fuels that ranges from 15% to 55%. The ‘frozen technology’ scenario is based on fleet technology frozen at 2018 and includes the benefits of fleet renewal, where airlines make substantial investments towards the acquisition of new aircraft.

At the third ICAO Conference on Aviation and Alternative Fuels in November 2023, ICAO adopted a new Global Framework for sustainable aviation fuels (SAF), lower carbon aviation fuels (LCAFs) and other aviation cleaner energies. To support the achievement of the long-term global aspirational goal (LTAG), ICAO and its Member States agreed to “strive to achieve a collective global aspirational vision to reduce CO₂ emissions in international aviation by 5% by 2030 through the use of SAF, LCAF and other aviation cleaner energies (compared to zero cleaner energy use).”

The Intergovernmental Panel on Climate Change (IPCC) is a scientific body of the United Nations (UN). It was created in 1988 by the World Meteorological Organization and the United Nations Environment Programme. It is the UN body for assessing the science of climate change. The IPCC provides policy makers with regular scientific assessments on climate change, its implications, and potential future risks. It also provides options for adaptation and mitigation. These reports are relevant to policy, but they are politically neutral and not prescriptive.

The UK Government fully supports the work of the IPCC. It regards the IPCC’s assessments as the most authoritative view on the science of climate change. IPCC assessments informed the creation of the United Nations Framework Convention on Climate Change (UNFCCC), and the subsequent Kyoto Protocol. They drove the Paris Agreement’s goal to limit temperature rises to well below 2°C and pursue efforts to limit the increase to 1.5°C, as well as underpinning the Glasgow Climate Pact agreed at COP26 (the 2021 United Nations Climate Change Conference) in November 2021. The 2018 IPCC Special Report on Global Warming of 1.5°C was a major influence on the UK’s net zero 2050 target and led to net zero targets being set around the world. ICAO, IPCC and UNFCCC work closely together and ICAO contributes to the UNFCCC process and Conference of the Parties (known as ‘COP’).

Paris Agreement 

In 2015, 195 parties to the UNFCCC adopted the Paris Agreement. It is a legally binding, international treaty which entered into force in November 2016. Its overarching goal is to hold the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change. Limiting global warming to 1.5°C or 2°C requires reducing global carbon dioxide emissions to at least net zero by around 2050 and 2070, respectively.

Under the Paris Agreement, participating parties are required to submit a national climate action plan, known as a Nationally Determined Contribution (NDC). These are to be submitted every five years under Article 4 of the Paris Agreement. NDCs set targets for mitigating against greenhouse gas emissions that cause climate change and for adapting to climate impacts. NDCs conventionally exclude international aviation emissions, which are instead the responsibility of ICAO. At COP26, Parties resolved to pursue efforts to limit global temperature rise to 1.5°C and agreed to revisit and strengthen the 2030 targets in their NDCs as necessary to align with the Paris Agreement temperature goal.