Editing IPCC:AR6/WGIII/Chapter-14 (section)

==== 14.5.2.3 Transportation ====

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The transportation sector has been a particular focus of cooperative efforts on climate mitigation that extend beyond the sphere of the UNFCCC climate regime. A number of these cooperative efforts involve transnational public-private partnerships, such as the European-based Transport Decarbonisation Alliance, which brings together countries, regions, cities and companies working towards the goal of a ‘net-zero emission mobility system before 2050’ ( [[#TDA--2019|TDA 2019]] ). Other efforts are centred in specialised UN agencies, such as the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO).

Measures introduced by the ICAO and IMO have addressed CO 2 emissions from international shipping and aviation. Emissions from these parts of the transportation sector are generally excluded from national emissions reduction policies and NDCs because the ‘international’ location of emissions release makes allocation to individual nations difficult ( [[#Bows-Larkin--2015|Bows-Larkin 2015]] ; [[#Lyle--2018|Lyle 2018]] ; [[#Hoch--2019|Hoch et al. 2019]] ). The measures adopted by ICAO take the form of standards and recommended practices that are adopted in national legislation. IMO publishes ‘regulations’ but does not have a power of enforcement, with non-compliance a responsibility of flag states that issue a ship’s ‘MARPOL’ certificate.

As discussed in [[IPCC:Wg3:Chapter:Chapter-2|Chapter 2]] and Figure SPM.4, international aviation currently accounts for approximately 1% of global GHG emissions, with international shipping contributing 1.2% of global GHG emissions. These international transport emissions are projected to be between approximately 60% and 220% of global emissions of CO 2 in 2050, as represented by the four main illustrative model pathways in SR1.5 ( [[#Rogelj--2018|Rogelj et al. 2018]] ; [[#UNEP--2020|UNEP 2020]] ) Notably, however, the climate impact of aviation emissions is estimated to be two to four times higher due to non-CO 2 effects ( [[#Terrenoire--2019|Terrenoire et al. 2019]] ; [[#Lee--2021a|Lee et al. 2021a]] ). Increases in trans-Arctic shipping and tourism activities with sea ice loss are also forecast to have strong regional effects due to ships’ gas and particulate emissions ( [[#Stephenson--2018|Stephenson et al. 2018]] ).

The Kyoto Protocol required Annex I Parties to pursue emissions reductions from aviation and marine bunker fuels by working through IMO and ICAO ( [[#UNFCCC--1997|UNFCCC 1997]] , Art. 2.2). Limited progress was made by these organisations on emissions controls in the ensuing decades ( [[#Liu--2011b|Liu 2011b]] ), but greater action was prompted by conclusion of the SDGs and Paris Agreement ( [[#Martinez%20Romera--2016|Martinez Romera 2016]] ), together with unilateral action, such as the EU’s inclusion of aviation emissions in its Emissions Trading System ( [[#Dobson--2020|Dobson 2020]] ).

The Paris Agreement neither explicitly addresses emissions from international aviation and shipping, nor repeats the Kyoto Protocol’s provision requiring Parties to work through ICAO/IMO to address these emissions ( [[#Hoch--2019|Hoch et al. 2019]] ). This leaves unclear the status of the Kyoto Protocol’s Article 2.2 directive after 2020 ( [[#Martinez%20Romera--2016|Martinez Romera 2016]] ; [[#Dobson--2020|Dobson 2020]] ), potentially opening up scope for more attention to aviation and shipping emissions under the Paris Agreement ( [[#Doelle--2019|Doelle and Chircop 2019]] ). Some commentators have suggested that emissions from international aviation and shipping should be part of the Paris Agreement ( [[#Gençsü--2015|Gençsü and Hino 2015]] ; [[#Traut--2018|Traut et al. 2018]] ), and shipping and aviation industries themselves may prefer emissions to be treated under an international regime rather than a nationally-oriented one ( [[#Gilbert--2012|Gilbert and Bows 2012]] ). In the case of shipping emissions, there is nothing in the Paris Agreement to prevent a Party from including international shipping in some form in its NDC ( [[#Doelle--2019|Doelle and Chircop 2019]] ) Under the Paris Rulebook, Parties ‘should report international aviation and marine bunker fuel emissions as two separate entries and should not include such emissions in national totals but report them distinctly, if disaggregated data are available’ ( [[#UNFCCC--2019d|UNFCCC 2019d]] ).

ICAO has an overarching climate goal to ‘limit or reduce the impact of aviation greenhouse gas emissions on the global climate’ with respect to international aviation. In order to achieve this, ICAO has two global aspirational goals for the international aviation sector, of 2% annual fuel efficiency improvement through 2050 and carbon neutral growth from 2020 onwards ( [[#ICAO--2016|ICAO 2016]] ). In order to achieve these global aspirational goals, ICAO is pursuing a ‘basket’ of mitigation measures for the aviation sector consisting of technical and operational measures, such as a CO 2 emissions standard for new aircraft adopted in 2016, measures on sustainable alternative fuels and a market-based measure, known as the Carbon Offset and Reduction Scheme for International Aviation (CORSIA), which the triennial ICAO Assembly of 193 Member States resolved to establish in 2016 ( [[#ICAO--2016|ICAO 2016]] ). In line with the 2016 ICAO Assembly Resolution that established CORSIA, in mid-2018, the ICAO’s 36-member state governing Council adopted a series of Standards and Recommended Practices (SARPs), now contained in Annex 16, Volume IV of the Chicago Convention (1944), as a common basis for CORSIA’s implementation and enforcement by each state and its aeroplane operators. From 1 January 2019, the CORSIA SARPs require states and their operators to undertake an annual process of monitoring, verification, and reporting of emissions from all international flights, including to establish CORSIA’s emissions baseline ( [[#ICAO--2019|ICAO 2019]] ).

Based on this emissions data, CORSIA’s carbon offsetting obligations commenced in 2021, with three-year compliance cycles, including a pilot phase in 2021–2023. States have the option to participate in the pilot phase and the subsequent voluntary three-year cycle in 2024–2026. CORSIA becomes mandatory from 2027 onwards for states whose share in the total international revenue tonnes per kilometre is above a certain threshold ( [[#Hoch--2019|Hoch et al. 2019]] ). Under CORSIA, aviation CO 2 emissions are not capped, but rather emissions that exceed the CORSIA baseline are compensated through use of ‘offset units’ from emissions reduction projects in other industries ( [[#Erling--2018|Erling 2018]] ). However, it is unclear whether the goal of carbon neutral growth and further CO 2 emissions reduction in the sector will be sufficiently incentivised solely through the use of such offsets in combination with ICAO’s manufacturing standards, programmes, and state action plans, without additional measures being taken, for example, constraints on demand ( [[#Lyle--2018|Lyle 2018]] ). If countries such as China, Brazil, India and Russia do not participate in CORSIA’s voluntary offsetting requirements this could significantly undermine its capacity to deliver fully on the sectoral goal by limiting coverage of the scheme to less than 50% of international aviation CO 2 emissions in the period 2021–2026 ( [[#Hoch--2019|Hoch et al. 2019]] ; [[#Climate%20Action%20Tracker--2020b|Climate Action Tracker 2020b]] ). In addition, a wide range of offsets are approved as ‘eligible emissions units’ in CORSIA, including several certified under voluntary carbon offset schemes, which may go beyond those eventually agreed under the Paris Agreement Article 6 mechanism ( [[#Hoch--2019|Hoch et al. 2019]] ). It is noted, however, that ICAO applies a set of ‘Emissions Unit Eligibility Criteria’, agreed in March 2019, which specify required design elements for eligible programmes. In June 2020, the ICAO Council decided to define 2019 emissions levels, rather than an average of 2019 and 2020 emissions, as the baseline year for at least the first three years of CORSIA, although there were significant reductions (45–60%) in aviation CO 2 emissions in 2020 compared with 2019 as a result of reductions in air travel associated with the COVID-19 pandemic ( [[#Climate%20Action%20Tracker--2020b|Climate Action Tracker 2020b]] ).

Other measures adopted by ICAO include an aircraft CO 2 emissions standard that applies to new aircraft type designs from 2020, and to aircraft type designs already in production as of 2023 ( [[#Smith--2018|Smith and Ahmad 2018]] ). Overall, CORSIA and regional measures, such as the EU ETS, are estimated to reduce aviation carbon emissions by only 0.8% per year from 2017–2030 (noting, however, that ‘if non-CO 2 emissions are included in the analysis, then emissions will increase’) ( [[#Larsson--2019|Larsson et al. 2019]] ). Accordingly, pathways consistent with the temperature goal of the Paris Agreement are likely to require more stringent international measures for the aviation sector ( [[#Larsson--2019|Larsson et al. 2019]] ).

Similar to ICAO, the IMO has a stated vision of remaining committed to reducing greenhouse gas emissions from international shipping and, as a matter of urgency, aims to phase them out as soon as possible in this century. IMO has considered a range of measures to monitor and reduce shipping emissions. In 2016, the IMO’s Marine Environment Protection Committee (MEPC) approved an amendment to the MARPOL Convention Annex VI for the introduction of a mandatory global data collection scheme for fuel oil consumption of ships ( [[#Dobson--2020|Dobson 2020]] ). Other IMO measures have focused on energy efficiency ( [[#Martinez%20Romera--2016|Martinez Romera 2016]] ). The IMO’s Energy Efficiency Design Index (EEDI), which is mandatory for new ships, is intended, over a ten-year period, to improve energy efficiency by up to 30% in several categories of ships propelled by diesel engines ( [[#Smith--2018|Smith and Ahmad 2018]] ). In May 2019, the MEPC approved draft amendments to the MARPOL Convention Annex VI, which if adopted, will bring forward the entry into force of the third phase of the EEDI requirements to 2022 instead of 2025 ( [[#IMO--2019|IMO 2019]] ; [[#Joung--2020|Joung et al. 2020]] ).

However, it is unlikely that the EEDI and other IMO technical and operational measures will be sufficient to produce ‘the necessary emissions reduction because of the future growth in international seaborne trade and world population’ ( [[#Shi--2018|Shi and Gullett 2018]] ). Consequently, in 2018, the IMO adopted an initial strategy on reduction of GHG emissions from ships ( [[#IMO--2018|IMO 2018]] ). This includes a goal for declining carbon intensity of the sector by reducing CO 2 emissions per transport work, as an average across international shipping, by at least 40% by 2030, and pursuing efforts towards 70% by 2050, compared to 2008 levels ( [[#IMO--2018|IMO 2018]] , Para. 3.1). The strategy also aims for peaking of total annual GHG emissions from international shipping as soon as possible and a reduction by at least 50% by 2050 compared to 2008 levels, while pursuing efforts towards phasing them out ‘as soon as possible in this century’ as a point ‘on a pathway of CO 2 emissions reduction consistent with the Paris Agreement temperature goals’ ( [[#IMO--2018|IMO 2018]] , Para. 2, 3.1). The shipping industry is on track to overachieve the 2030 carbon intensity target but not its 2050 target ( [[#Climate%20Action%20Tracker--2020c|Climate Action Tracker 2020c]] ). The initial IMO strategy is to be kept under review by the MEPC with a view to adoption of a revised strategy in 2023.

The IMO’s initial strategy identifies a series of candidate short-term (2018–2023), medium-term (2023–2030) and long-term (beyond 2030) measures for achieving its emissions reduction goals, including possible market-based measures in the medium-to-long term ( [[#IMO--2018|IMO 2018]] , paras. 4.7–4.9). Further progress on market-based measures faces difficulty in light of conflicts between the CBDRRC principle of the climate regime and the traditional non-discrimination approach and principle of no more favourable treatment enshrined in MARPOL and other IMO conventions ( [[#Zhang--2016|Zhang 2016]] ). Both the CBDRRC and non-discrimination principles are designated as ‘principles guiding the initial strategy’ ( [[#IMO--2018|IMO 2018]] , Para. 3.2). The challenges encountered in introducing global market-based measures for shipping emissions under the IMO have prompted regional initiatives such as the proposed extension of the EU ETS to emissions from maritime activities ( [[#Christodoulou--2021|Christodoulou et al. 2021]] ), which was announced on 14 July 2021 by the EU Commission as part of its ‘Fit for 55’ legislative package ( [[#European%20Commission--2021|European Commission 2021]] ).

While the IMO strategy is viewed as a reasonable first step that is ambitious for the shipping industry, achieving the ‘vision’ of alignment with the temperature goals of the Paris Agreement requires concrete implementation measures and strengthened targets in the next iteration in 2023 ( [[#Doelle--2019|Doelle and Chircop 2019]] ; [[#Climate%20Action%20Tracker--2020c|Climate Action Tracker 2020c]] ). As a step towards this, in 2020, the IMO’s MEPC put forward draft amendments to the MARPOL Convention that would require ships to combine a technical and an operational approach to reduce their carbon intensity. These amendments were formally adopted by the Committee at its session in June 2021.

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