Aviation CO2 Emissions Research Articles

The pathway to net-zero emission in aviation – How much can we rely on sustainable aviation fuel?

The aviation industry is under constant pressure to reduce its environmental footprint and eventually achieve net-zero carbon emissions by 2050. In order to accomplish this ambitious but necessary goal, a variety of measures have been employed over the last two decades, among which the application of sustainable aviation fuels (SAFs) plays a prominent role. Policymakers aim at substituting 80-90% of aviation fuel by SAF in 2050, thus reducing global aviation CO2 emissions by 62%. In theory, these fuels can already be integrated in up to 50% of the fuel capacity of current aircraft as “drop-in” fuels. However, due to numerous operational and regulatory barriers surrounding the exploitation of SAF, it is still not clear how, in combination with traditional jet fuel, it will affect the cost aspect of airline operations. Considering the traffic projection provided by EUROCONTROL according to which the traffic will undoubtedly increase in the next decade, the aim of the paper is to provide a preliminary assessment of the financial impact of SAF on an airline's total fuel cost. For this purpose, the analysis is based on a single carrier that follows a hybrid business model and mainly focuses its operation on intra-European routes. Creating different scenarios for SAF's future costs as well as the share of SAF in total fuel required, this paper provides some realistic results that may serve as a solid foundation for the airline to better understand the implications of SAF on its financial aspects, keeping in mind that fuel costs still constitute a large portion in an airline's direct operating costs. The proposed methodology may be applied to any carrier with an interest in SAF.

From Takeoff to Touchdown: A Decade’s Review of Carbon Emissions from Civil Aviation in China’s Expanding Megacities

The rapid growth of urbanization in China has led to a substantial escalation in the demand for civil aviation services, consequently propelling China to the third-largest contributor of carbon emissions within the aviation sector. Using the 2012–2021 data on takeoffs and landings of civil aviation aircraft in China, the aircraft engine emission factor database of the Base of Aircraft Data (BADA) from EUROCONTROL, this paper investigates the spatial-temporal distribution characteristics of atmospheric pollutants, primarily carbon emissions from Chinese civil aviation aircraft in 19 megacities. The results indicate that (1) China’s aviation CO2 emissions equivalent between 2012 and 2022 has been on an upward trajectory, peaking at 186.53 MT in 2019 with an average annual growth of 12.52%. The trend, albeit momentarily interrupted by the COVID-19 pandemic, appears to persist. (2) CO2 constitutes the highest proportion of aircraft emissions at 83.87%, with Cruise Climb Descent (CCD) cycle emissions accounting for 96.24%. CO2 and NOX, with the highest increase rates in the CCD and Landing and Takeoff (LTO) phases, respectively, are identified as the chief culprits in aviation-related greenhouse effects. (3) There is a marked spatial imbalance, with 19 megacities contributing 62.08% of total CO2 emissions, compared to the 207 least-emitting cities contributing just 9.29%. (4) The pattern of city carbon emissions is changing, with rapid growth rates in the western cities of Xinjiang, Tibet, Shaanxi, and Guizhou, and varied growth rates among megacities. The implications of this study emphasize the urgency for advancements in aviation fuel technology, rigorous management of CCD phase pollutants, strategic carbon emission controls in populous cities, fostering green aviation initiatives in western regions, diverse carbon mitigation tactics, and strengthening the precision and surveillance of aviation carbon accounting systems. Collectively, this study paints a grand picture of the complexities and challenges associated with China’s urban sprawl and aviation carbon emissions.

A market-based framework for CO2 emissions reduction in China's civil aviation industry

This paper proposes a novel aviation CO2 emissions reduction method by introducing a market-based incentive mechanism. An aviation carbon emissions prediction model is proposed to characterize both the microscopic flight dynamics and the macroscopic air traffic demand trend. Based on emissions prediction, a linear climate response model is applied to evaluate the environmental impact of the aviation carbon emissions. Finally, a market-based framework for aviation CO2 emissions reduction is established based on a two-phase carbon trading model, which provides a piecewise charge method through emission taxation and cap-and-trade. A case study is carried out to demonstrate the effectiveness of the proposed framework using a real-world dataset from the Hefei Air Traffic Control Zone in China. Three scenarios are defined to describe the possible development speed of sustainable aviation fuel application in the future: not applied, medium-speed development, and high-speed development. The results show that the carbon peak will be reached in 2025 in the high-speed development scenario, when the emission amount and associated environmental impact will be reduced by 23.7% and 22.3%, respectively. Thus, the market-based framework proposed in this paper can effectively reduce aviation CO2 emissions and mitigate the effects of global warming.

Predicting the climate impact of aviation for en-route emissions: the algorithmic climate change function submodel ACCF 1.0 of EMAC 2.53

Abstract. Using climate-optimized flight trajectories is one essential measure to reduce aviation's climate impact. Detailed knowledge of temporal and spatial climate sensitivity for aviation emissions in the atmosphere is required to realize such a climate mitigation measure. The algorithmic Climate Change Functions (aCCFs) represent the basis for such purposes. This paper presents the first version of the Algorithmic Climate Change Function submodel (ACCF 1.0) within the European Centre HAMburg general circulation model (ECHAM) and Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model framework. In the ACCF 1.0, we implement a set of aCCFs (version 1.0) to estimate the average temperature response over 20 years (ATR20) resulting from aviation CO2 emissions and non-CO2 impacts, such as NOx emissions (via ozone production and methane destruction), water vapour emissions, and contrail cirrus. While the aCCF concept has been introduced in previous research, here, we publish a consistent set of aCCF formulas in terms of fuel scenario, metric, and efficacy for the first time. In particular, this paper elaborates on contrail aCCF development, which has not been published before. ACCF 1.0 uses the simulated atmospheric conditions at the emission location as input to calculate the ATR20 per unit of fuel burned, per NOx emitted, or per flown kilometre. In this research, we perform quality checks of the ACCF 1.0 outputs in two aspects. Firstly, we compare climatological values calculated by ACCF 1.0 to previous studies. The comparison confirms that in the Northern Hemisphere between 150–300 hPa altitude (flight corridor), the vertical and latitudinal structure of NOx-induced ozone and H2O effects are well represented by the ACCF model output. The NOx-induced methane effects increase towards lower altitudes and higher latitudes, which behaves differently from the existing literature. For contrail cirrus, the climatological pattern of the ACCF model output corresponds with the literature, except that contrail-cirrus aCCF generates values at low altitudes near polar regions, which is caused by the conditions set up for contrail formation. Secondly, we evaluate the reduction of NOx-induced ozone effects through trajectory optimization, employing the tagging chemistry approach (contribution approach to tag species according to their emission categories and to inherit these tags to other species during the subsequent chemical reactions). The simulation results show that climate-optimized trajectories reduce the radiative forcing contribution from aviation NOx-induced ozone compared to cost-optimized trajectories. Finally, we couple the ACCF 1.0 to the air traffic simulation submodel AirTraf version 2.0 and demonstrate the variability of the flight trajectories when the efficacy of individual effects is considered. Based on the 1 d simulation results of a subset of European flights, the total ATR20 of the climate-optimized flights is significantly lower (roughly 50 % less) than that of the cost-optimized flights, with the most considerable contribution from contrail cirrus. The CO2 contribution observed in this study is low compared with the non-CO2 effects, which requires further diagnosis.

CO2 emission change in China’s aviation industry: A fleet-wide index decomposition and scenario analysis

A fleet-wide index decomposition and scenario analysis model is developed to identify the influencing factors of CO2 emission change in China’s aviation industry and predict CO2 emissions in multiple emission reduction scenarios through 2040. It was discovered that all aircraft types experienced operational improvements during 2009 and 2019. The fleet utilization growth resulted in the most of CO2 emission reduction. However, slowdown in fleet updates existed for most of aircraft types, and the decreased fleet fuel intensity only resulted in CO2 emission reduction in specific years. The rising air transport demand continues to be the greatest obstacle to reducing emissions. Under the baseline scenario, aviation carbon intensity can only realize the 60–65% target by 2035. With endeavours on traffic demand control and technology, aviation CO2 emissions will peak at 123 Mt in 2035. The rapid sustainable alternative fuels substitutions will be essential for achieving China’s 35–40% target before 2040.

The substitution effect of high-speed rail on civil aviation in China

China's high-speed rail (HSR) network has had a marked effect on civil aviation transport and CO2 emissions. We conduct a quantitative analysis of the substitution effect during the period 2008–2017 using the difference-in-difference method. We find that (1) the introduction and operation of the HSR network of four vertical and four horizontal lines has had a significantly negative effect on the civil aviation service. Overall, the numbers of passenger flights and air passengers fell by 28.7% and 31.8%, respectively, following the introduction of HSR. (2) HSR is most competitive when trip or operating times are less than 4 h (3) For operating times within 6 h, or trips of about 1400 km, HSR enjoys an obvious competitive advantage over civil aviation. (4) Planning is underway for an expanded HSR network comprising eight vertical and eight horizontal lines. On completion, an additional 833 flight routes compared with the current HSR network and the rate of substitution of HSR for civil aviation flights will increase by 8.8%. Taking into account an increase in rail speed for passages along rivers and coastal areas, the substitution rate of HSR will increase by a further 0.7%. (5) HSR development will have obvious CO2 emissions reduction effect on aviation transport.

Cost and emissions pathways towards net-zero climate impacts in aviation

Aviation emissions are not on a trajectory consistent with Paris Climate Agreement goals. We evaluate the extent to which fuel pathways—synthetic fuels from biomass, synthetic fuels from green hydrogen and atmospheric CO2, and the direct use of green liquid hydrogen—could lead aviation towards net-zero climate impacts. Together with continued efficiency gains and contrail avoidance, but without offsets, such an energy transition could reduce lifecycle aviation CO2 emissions by 89–94% compared with year-2019 levels, despite a 2–3-fold growth in demand by 2050. The aviation sector could manage the associated cost increases, with ticket prices rising by no more than 15% compared with a no-intervention baseline leading to demand suppression of less than 14%. These pathways will require discounted investments on the order of US$0.5–2.1 trillion over a 30 yr period. However, our pathways reduce aviation CO2-equivalent emissions by only 46–69%; more action is required to mitigate non-CO2 impacts. Decarbonization of the aviation sector is difficult due to increasing demand and the current lack of scalable mitigation technologies. This Analysis examines pathways towards a net-zero aviation system with improved fuel and aircraft technologies, efficiency gains and contrail avoidance.

An emissions inventory using flight information reveals the long-term changes of aviation CO2 emissions in China

The low-carbon development of air transport industry is of great significance for China to achieve the commitment of carbon peak and carbon neutrality goals. In order to improve the basic data of aviation CO2 emissions, this study continuously collected full flight information in China from January 2017 to December 2020, and established a flight information database and an aircraft-engine parameter database. On the basis of IPCC's Tier 3B accounting method, this study established a long-term aviation CO2 emissions inventory of China from 2017 to 2020 by calculating and accumulating CO2 emissions of each flight. And aviation CO2 emissions of various provinces and cities in China were calculated combined with spatial allocation method. The results showed that aviation CO2 emissions in China was 104.1, 120.1, 136.9, and 88.3 Mt in 2017, 2018, 2019, and 2020, respectively, with annual growth rates of 15.4%, 14.0%, and −35.3% in 2018, 2019, and 2020, respectively. Affected by the COVID-19 pandemic, aviation CO2 emissions in all 31 provinces and 93% of cities decreased in 2020 compared with 2019. China is in the stage of rapid development of air transport industry, and aviation fossil energy consumption and CO2 emissions have continued to grow in recent years.

Carbon dioxide emissions from international air transport of people and freight: New Zealand as a case study

International aviation accounts for over 2% of global emissions, but was not subject to Kyoto Protocol liabilities, and was not directly addressed by the Paris Agreement. Calculating emissions associated with individual countries is complicated, with data that is publicly available and free to access often being difficult to obtain. In this paper, a case study is presented where commercially sensitive fuel uplift is used to calculate New Zealand specific emissions factors of 0.81 kg CO2 per tonne km (CO2 per t-km) for short-haul and 0.79 kg CO2 per t-km for long-haul international aviation. This was used to estimate international aviation CO2 emissions associated with New Zealand in 2017 to be 8.4 Mt CO2 in total (2 significant figures, rounded down), with international visitor travel to and from New Zealand accounting for 4.3 Mt CO2, New Zealand residents’ international travel for 2.6 Mt CO2, exports for 0.72 Mt CO2, and imports for 0.89 Mt CO2 (all 2 significant figures, rounded up). Results show the fleet of aeroplanes which serviced New Zealand between 2007 and 2017 has become, on average, less efficient due to changes in operational factors such as seating density.

A Bottom-Up Emissions Inventory Reveals the Long-Term Changes of Aviation Co2 Emissions in Chinese Cities

A Bottom-Up Emissions Inventory Reveals the Long-Term Changes of Aviation Co2 Emissions in Chinese Cities

Особливості, проблеми та перспективи декарбонізації цивільної авіації

Abstract. The article considers the peculiarities of the process of decarbonization of civil aviation. The objectives presented by IATA to the UN Framework Convention on Reducing Carbon Emissions have been clarified: a) average increase in fuel efficiency by 1.5 % per year from 2009 to 2023; b) a cap on net aviation CO₂ emissions from 2020 (carbon-neutral growth); c) a 50 % reduction in net aviation CO₂ emissions by 2050 compared to 2005 levels. These goals can be achieved by following four decarbonisation strategies: the operational efficiency of airlines, the use of innovative technologies, the use of sustainable energy fuels and carbon offset measures. According to the results of the analysis, the operational efficiency strategy provides for: route optimization; increasing the occupancy and load factor of aircraft; weight loss on board; fleet renewal; acquisition of new generation aircraft (eg A320NEO), which is projected to reduce life cycle CO₂ emissions per aircraft by 1-15 %. Sustainable aviation fuel (SAFs) strategy: biofuels; synthetic fuel; hydrogen and electric fuels can reduce carbon emissions by 13-26 %. Most of all, it can reduce carbon emissions, namely by 30-70 % of the use of electric or hybrid aircraft. The carbon offset strategy complements other measures to reduce CO₂ emissions that cannot be reduced through the use of technological improvements, operational improvements and SAFs through compensation payments for exceeding carbon emissions. It is established that the process of decarbonization of civil aviation is based on such principles as: 1) decarbonization and strategic foresight; 2) implementation of environmental behavior in practice; 3) increasing regulatory flexibility; 4) accelerated creation of partnerships focused on climate protection; 5) digitization of data and processes to build trust and confirm results. The problem with the process of decarbonization of civil aviation is that fully electric, hybrid-electric and environmentally friendly commercial airliners operating on hydrogen are far from mass production due to flight physics, safety test requirements and current technological constraints. Sustainable aviation fuel will provide significant opportunities to reduce greenhouse gas emissions from aviation, but it is currently produced to a limited extent and requires significant commercial development to achieve widespread use. On the positive side, reducing greenhouse gas emissions for civil aviation companies in the long run will mean improving their business reputation, diversifying their investor base, raising stock prices, reducing the cost of raising capital and expanding investment opportunities. In the following researches it is offered to make the analysis of influence of decarbonization on the basic financial and economic indicators of the enterprises of branch of civil aviation. Keywords: global warming, decarbonisation strategy, greenhouse gases, carbon-neutral growth, sustainable aviation fuel, operational efficiency, innovative technologies, carbon offset.

External Aspects of the EU ETS in Aviation in Light of CORSIA

Abstract According to International Civil Aviation Organization (ICAO) Assembly Resolution A40-19, the Carbon Offsetting and Reduction Scheme for International Aviation mechanism (CORSIA) is to be the only global market-based measure (MBM) applied to CO2 emissions from international aviation. This solution has been dictated by the intention to avoid a patchwork of duplicative State or regional MBMs and to ensure that international aviation CO2 emissions should be accounted for only once. The present contribution assesses the margin of autonomy left for Emissions Trading System of the EU (EU ETS) mechanism in the light of this clause, considering its legal status and divergent interpretations. Moreover, the recent 2020 roadmap for revision of the EU ETS Directive concerning aviation, published by the European Commission, is briefly discussed.

Effects of railway speed on aviation demand and CO2 emissions in China

While there is a rich body of literature on the impact of high-speed rail (HSR) on aviation, research on railway speedup and the consequent environmental effects remains scarce. We apply an augmented gravity model to examine the effect of railway speedup on air travel demand and CO2 emissions for 546 city pairs from 2013 to 2017. We observe that, on average, railway weighted operation speed increased from 100.9 km/h in 2013 to 141.2 km/h in 2017. As railway operation speed increased by 39.94%, the number of airline passengers declined by 29.84% for all market segments. During the research period, about 104.92 million air passengers shifted to rail transport due to improved rail services driven by speed, leading to a reduction of 13.57 million tons of CO2 emissions. Our findings highlight the importance of optimizing transportation structure to reduce CO2 emissions.

The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018

Global aviation operations contribute to anthropogenic climate change via a complex set of processes that lead to a net surface warming. Of importance are aviation emissions of carbon dioxide (CO2), nitrogen oxides (NOx), water vapor, soot and sulfate aerosols, and increased cloudiness due to contrail formation. Aviation grew strongly over the past decades (1960–2018) in terms of activity, with revenue passenger kilometers increasing from 109 to 8269 billion km yr−1, and in terms of climate change impacts, with CO2 emissions increasing by a factor of 6.8 to 1034 Tg CO2 yr−1. Over the period 2013–2018, the growth rates in both terms show a marked increase. Here, we present a new comprehensive and quantitative approach for evaluating aviation climate forcing terms. Both radiative forcing (RF) and effective radiative forcing (ERF) terms and their sums are calculated for the years 2000–2018. Contrail cirrus, consisting of linear contrails and the cirrus cloudiness arising from them, yields the largest positive net (warming) ERF term followed by CO2 and NOx emissions. The formation and emission of sulfate aerosol yields a negative (cooling) term. The mean contrail cirrus ERF/RF ratio of 0.42 indicates that contrail cirrus is less effective in surface warming than other terms. For 2018 the net aviation ERF is +100.9 milliwatts (mW) m−2 (5–95% likelihood range of (55, 145)) with major contributions from contrail cirrus (57.4 mW m−2), CO2 (34.3 mW m−2), and NOx (17.5 mW m−2). Non-CO2 terms sum to yield a net positive (warming) ERF that accounts for more than half (66%) of the aviation net ERF in 2018. Using normalization to aviation fuel use, the contribution of global aviation in 2011 was calculated to be 3.5 (4.0, 3.4) % of the net anthropogenic ERF of 2290 (1130, 3330) mW m−2. Uncertainty distributions (5%, 95%) show that non-CO2 forcing terms contribute about 8 times more than CO2 to the uncertainty in the aviation net ERF in 2018. The best estimates of the ERFs from aviation aerosol-cloud interactions for soot and sulfate remain undetermined. CO2-warming-equivalent emissions based on global warming potentials (GWP* method) indicate that aviation emissions are currently warming the climate at approximately three times the rate of that associated with aviation CO2 emissions alone. CO2 and NOx aviation emissions and cloud effects remain a continued focus of anthropogenic climate change research and policy discussions.

Impact of Carbon Tax Scheme and CO2 Control Technologies on Bangladesh Aviation Industry

Aviation transport action group reported that carbon dioxide (CO2 ) emission of airlines in 2017 was 859 million tons which is 2% of global emissions, (Akça, Z. 2018). It adds that the bank has calculated that “under the worst case ‘carbon intensive’ scenario, living standards will fall by 6.7% for Bangladesh by 2050”. This paper investigates how Bangladesh can respond to best optimize to the EU’s Aviation Carbon Tax Scheme proposed by the Stackelberg game model. The analytic result shows that the strategy “refusal of pay” is the best one which Bangladesh is taking step of. Numerical simulations specify a quantitative visual of the consequences found. The policy is found to be effectively not flying as much would reduce the CO2 emission and consequently, purchase of new aircraft, retrofitting and upgrade improvements on existing aircraft, latest designs in aircraft/engines, fuel efficiency standards and alternative fuels etc. reducing the overall emissions. The main contribution of this paper is to study a new international issue for developing country on aviation carbon tax and CO2 emissions policy suggestions for the aviation technology.

Mitigating the Climate Forcing of Aircraft Contrails by Small-Scale Diversions and Technology Adoption.

The climate forcing of contrails and induced-cirrus cloudiness is thought to be comparable to the cumulative impacts of aviation CO2 emissions. This paper estimates the impact of aviation contrails on climate forcing for flight track data in Japanese airspace and propagates uncertainties arising from meteorology and aircraft black carbon (BC) particle number emissions. Uncertainties in the contrail age, coverage, optical properties, radiative forcing, and energy forcing (EF) from individual flights can be 2 orders of magnitude larger than the fleet-average values. Only 2.2% [2.0, 2.5%] of flights contribute to 80% of the contrail EF in this region. A small-scale strategy of selectively diverting 1.7% of the fleet could reduce the contrail EF by up to 59.3% [52.4, 65.6%], with only a 0.014% [0.010, 0.017%] increase in total fuel consumption and CO2 emissions. A low-risk strategy of diverting flights only if there is no fuel penalty, thereby avoiding additional long-lived CO2 emissions, would reduce contrail EF by 20.0% [17.4, 23.0%]. In the longer term, widespread use of new engine combustor technology, which reduces BC particle emissions, could achieve a 68.8% [45.2, 82.1%] reduction in the contrail EF. A combination of both interventions could reduce the contrail EF by 91.8% [88.6, 95.8%].

Evaluation of carbon emission efficiency in China's airlines

Abstract Aviation CO2 emissions are increasing along with traffic growth, and expected technological improvements are not enough to reduce this continuous growth. In response to the rapid growth in air transport CO2 emissions, International Civil Aviation Organization has proposed the “Carbon Neutral Growth from 2020″ strategy to reduce aviation carbon emissions. Using 13 Chinese airlines data from 2009 to 2013, this study investigates the static and dynamic efficiencies of carbon emissions through the global slack based measure (GSBM) model and the Global Malmquist-Luenberger productivity index (GML). The results indicate that, first, the static efficiency of carbon emissions in airlines showed an inverted U-shaped trend during the inspection period. Second, the average values of dynamic carbon emissions efficiency of China's airlines in 2009–2013 are 1.098, 1.157, 0.995, and 0.950 respectively. Third, the reasons for the changes in the dynamic efficiency of each airline are different. Monitoring the carbon emissions efficiency of airlines may help the government to develop targeted carbon-reduction policies.

Acquiring and Geo-Visualizing Aviation Carbon Footprint among Urban Agglomerations in China

This paper had two main purposes. One was to estimate annual total aviation CO2 emissions from/among all key urban agglomerations (UAs) in China and its changes patterns from 2007 to 2014. The second one was to visualize the aviation carbon footprints among the UAs by using a chord diagram plot. This study also used Kaya identity to decompose the contribution of potential driving forces behind the aviation CO2 emissions using Kaya identity. Especially, it decomposed factor CO2/gross domestic product (GDP), which is wildly used in Kaya identity analysis, into factor CO2/value-added (VA) and factor VA/GDP. Here, VA represents the tourism value added of the corresponding flights. The main results were: (1) The UAs developed a much bigger and stronger carbon network among themselves. (2) There was also an expanding of the flows to less densely populated or less developed UAs. However, the regional disparity increased significantly. (3) Compared with the driving factor of population, the GDP per capita impacted the emission amount more significantly. Our contribution had two folds. First, it advances current knowledge by fulfilling the research gap between transport emissions and UA relationship. Second, it provides a new approach to visualizing the aviation carbon footprints as well as the relationships among UAs.

The contribution of carbon dioxide emissions from the aviation sector to future climate change

The compact Earth system model OSCARv2.2 is used to assess the climate impact of present and future civil aviation carbon dioxide (CO2) emissions. The impact of aviation CO2 on future climate is quantified over the 1940–2050 period, extending some simulations to 2100 and using different aviation CO2 emission scenarios and two background Representative Concentrations Pathways (RCP2.6 and RCP6.0) for other emission sectors. Several aviation scenarios including weak to strong mitigation options are considered with emissions ranging from 386 MtCO2/year (Factor 2 scenario) to 2338 MtCO2/year (ICAO based scenario) in 2050. As a reference, in 2000, the calculated impact of aviation CO2 emissions is 9.1 ± 2 mK (0.8% of the total anthropogenic warming associated to fossil fuel emissions). In 2050, on a climate trajectory in line with the Paris Agreement limiting the global warming below 2 °C (RCP2.6), the impact of the aviation CO2 emissions ranges from 26 ± 2 mK (1.4% of the total anthropogenic warming associated to fossil fuel emissions) for an ambitious mitigation strategy scenario (Factor 2) to 39 ± 4 mK (2.0% of the total anthropogenic warming associated to fossil fuel emissions) for the least ambitious mitigation scenario of the study (ICAO based). On the longer term, if no significant emission mitigation is implemented for the aviation sector, the associated warming could further increase and reach a value of 99.5 mK ± 20 mK in 2100 (ICAO based), which corresponds to 5.2% of the total anthropogenic warming under RCP2.6. The contribution of CO2 is estimated to represent 36%–51% of the total aviation radiative forcing of climate including short-term climate forcers. However, due to its long residence time in the atmosphere, aviation CO2 will have a major contribution on decadal time scales. These additional short-terms forcers are subject to large uncertainties and will be analysed in forthcoming studies.

A win-win solution to abate aviation CO2 emissions

We evaluate incentives for airlines to abate emissions under the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). We find that the scheme will not result in an efficient level of abatement and propose an additional measure that will incentivize in-sector emission abatement opportunities that cost less than the social cost of carbon (SCC). The proposed measure sets benchmark emission intensities (CO2 emissions per revenue ton kilometer) by route group and facilitates flexibility in meeting the benchmarks by allowing airlines to sell permits if they operate more efficiently than the benchmarks, and buy permits if they do not meet the benchmarks. The CO2 benchmark system could operate concurrently with existing measures to mitigate aviation CO2 emissions, will reduce the number of offsets needed to achieve carbon-neutral growth, and provide another (optional) lever to address fairness issues in climate regulations. Moreover, by providing a blueprint for other industries to price marginal emissions at the SCC, a CO2 benchmark system could preserve the ‘carbon budget’ for use by high-cost abatement industries such as the aviation industry.