ISAE-SUPAERO PUBLISHES AN AVIATION AND CLIMATE REVIEW

This 200-page report is the result of a year of work by a team of 5 teacher-researchers and the Institute’s head of sustainable development. Accompanied by a summary of approximately fifteen pages, it is based on more than 200 scientific publications and the latest reports from institutions in the aeronautics sector. The researchers completed this repository by integrating the research results specific to ISAE-SUPAERO. The entire document has been the subject of a rigorous review process, both internally and by recognized scientific experts in the sectors of aviation, climatology, energy, etc.
The drafting of this reference report was motivated by issues related to the impact of aviation on the climate. Can we characterize the impact of aviation on the climate? Can CO2 and non-CO2 effects be compared? What technological solutions are being studied today to make aviation sustainable? Can we link the speed of change in air traffic to the fraction of the carbon budget devoted to aviation? Can we make an assessment of available energy resources?

A COLLABORATIVE TOOL

The objective of this work is not to take sides or answer the various questions raised, because the answers depend largely on societal choices and technical-economic developments that are impossible to predict with certainty.

On the other hand, the aim is to provide everyone, from the position of scientists, with the elements necessary to build informed opinions on these questions, as objectively as possible. Scientists hope to spark debates and thus participate in the emergence of a collective position on these crucial issues.
This repository draws up an inventory of the various levers that the aviation sector can use to reduce this environmental impact.

KEY MESSAGES FOR A DECARBONIZED AVIATION

The ISAE-SUPAERO Aviation and Climate repository aims to provide scientific elements useful for understanding aviation and climate issues. It is divided into three main sections. The first presents the impact of aviation on the climate, its CO2 and non-CO2 effects, while the second part addresses the technological levers to reduce it. Finally, illustrative transition scenarios for the aviation sector are proposed in the last section. This latter is based in particular on CAST, an innovative modeling tool developed at ISAE-SUPAERO and available as a web application, used to assess the climate impact of aviation according to variables such as the volume of traffic, the pace of technological developments, or the rate of decarbonization of the fuel used.

• Climate impact of aviation: estimates that depend on the perimeter

Aviation contributes to accentuating global warming through its CO2 emissions and several non-CO2 effects such as contrails. An assessment of the air sector’s impact can be limited to CO2 emissions alone, or all the effects can be taken into account. In the first case, commercial aviation was responsible for 2.6 of the world’s anthropogenic CO2 emissions in 2018. If we consider all the effects (CO2 and non-CO2), commercial aviation accounted for 5.1% of the climate impact over the 2000-2018 period.

• Non-CO2 effects: promising strategies

Specific strategies for the reduction of non-CO2 effects provide a major lever for limiting aviation’s climate impact. Due to the short lifetime of non-CO2 effects, these strategies can be effective quite quickly. Even though more research is needed to reduce uncertainties, these strategies could be deployed in the short term. Nonetheless, these measures cannot replace efforts for reducing CO2 emissions in the sector.

• CO2 effects: limited technological opportunities in the short term

By 2050, breakthrough solutions should enable us to envisage low-carbon aircraft. In the shorter term, the only mature levers for reducing CO2 emissions within the time frames imposed by the climate emergency are incremental improvements in aircraft efficiency and the use of biofuels. Nonetheless, incremental improvements are coming up against technological limits, while the constraints of energy availability, production capacities and competition among uses risk reducing biofuel’s availability.

• Necessary arbitration between the amount of traffic and the share of the worldwide carbon budget allocated to the aviation sector

Beyond the technological and operational levers, the amount of traffic and the share of the worldwide carbon budget allocated to aviation are the two parameters that determine the sustainability of a pathway for the aviation sector. Their value must be set through political decisions. Limits to the aviation sector’s ability to rapidly reduce its CO2 emissions mean that if traffic grows at the rate foreseen by the aviation industry, it will consume a greater share of the carbon budget than its current share of emissions, thus requiring other sectors to reduce their emissions more quickly than the average.

• Uncertainties as to energy availability

The decarbonization of aviation fuels could be limited by the availability of low-carbon energy resources. Their massive use could then lead to a shift in the environmental problem, notably connected to land use. More generally, we need to think of the transition in the air sector from a systemic point of view in the context of our planet’s limits.

SCALABLE STRATEGIES

This repository highlights several conclusions. In particular, it reveals that cloud formation by aircraft condensation trails currently has a greater effect on warming than their CO2 emissions. However, it seems possible to drastically reduce these condensation trails by modifying the trajectories of a small proportion of flights: this subject, still little studied, must be deepened as soon as possible. For CO2 emissions, technical solutions are available to reduce them very sharply by further improving the energy efficiency of aircraft and switching to low-carbon fuels. However, it will take several decades to develop, industrialize and deploy these solutions to the entire fleet. Based on possible scenarios between now and 2050, the report highlights the relationship between the level of air traffic over the coming decades and the fraction of the global carbon budget allocated to aviation

This document is aimed at stakeholders in the aviation sector, to help them define their decarbonization strategies, while contributing to the public debate by shedding the most objective light possible on a both complex and important subject. To discover the ISAE-SUPAERO Aviation and Climate repository, go HERE.

REVIEW AND SUMMARY:

Photo of the team of 6 ISAE-SUPAERO authors: 5 teacher-researchers and the sustainable development manager