22. June 2021
Climate impact of air transport

Cur­rent air trans­port cli­mate tar­gets in­suf­fi­cient for trend re­ver­sal

Passenger aircraft in the clouds
Pas­sen­ger air­craft in the clouds
Image 1/2, Credit: DLR/Alejandro Morellon (CC-BY 3.0)

Passenger aircraft in the clouds

Re­search re­sults in re­cent years have in­creas­ing­ly shown that con­trails and ni­tro­gen ox­ides to­geth­er cause a greater cli­mate ef­fect from air trans­port than car­bon-diox­ide emis­sions alone.
Predicting the impact of air transport on global warming in different scenarios
Pre­dict­ing the im­pact of air trans­port on glob­al warm­ing in dif­fer­ent sce­nar­ios
Image 2/2, Credit: DLR (CC BY-NC-ND 3.0)

Predicting the impact of air transport on global warming in different scenarios

Cal­cu­lat­ed ground-lev­el tem­per­a­ture changes caused by air trans­port (in mil­likelvin) us­ing var­i­ous as­sump­tions about fu­ture de­vel­op­ments up to the end of the cen­tu­ry. The up­per es­ti­mate rep­re­sents the con­tin­ued use of present air­craft tech­nolo­gies (Cur­rent Tech­nol­o­gy). Oth­er es­ti­mates show a con­tin­u­a­tion of the pre­vi­ous in­creas­es in ef­fi­cien­cy (Busi­ness as Usu­al), car­bon-diox­ide-neu­tral growth from 2020 (COR­SIA) and the suc­cess­ful im­ple­men­ta­tion of the tar­gets pre­vi­ous­ly set out in Flight­path 2050. These are con­trast­ed with an as­sess­ment of pos­si­ble ar­eas of po­ten­tial for re­duc­tion on the ba­sis of ex­ist­ing tech­nol­o­gy con­cepts (ECATS) and the in­flu­ence of the COVID-19 pan­dem­ic if re­cov­ery oc­curs with­in 15 years, to­geth­er with a sus­tain­able shift in trav­el be­haviour. The five per­cent lim­it on the air trans­port con­tri­bu­tion to glob­al warm­ing has been set in re­la­tion to the Paris cli­mate tar­gets (lim­it­ing glob­al warm­ing to 1.5 de­grees Cel­sius or 2.0 de­grees Cel­sius com­pared to pre-in­dus­tri­al lev­els).
  • CORSIA offset programme is likely to miss aviation climate targets in support of the 1.5-degree Celsius Paris agreement.
  • This is due to the lack of inclusion of non-carbon-dioxide effects while the air transport sector is expected to grow.
  • Effect of COVID-19 pandemic on air transport climate impact is expected to be low as long as sector recovery is achieved within three to 15 years.
  • Focus: Aeronautics, climate-friendly flight

In 2016, the International Civil Aviation Organization (ICAO) set out climate protection targets for global air transport for the first time as part of its CORSIA programme . After 2020, air traffic should only be expanded in a climate-neutral way. In addition, the aim is to halve carbon dioxide emissions from air transport by 2050, compared to the base year of 2005. A research study led by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) has now concluded that the CORSIA targets have the potential to mitigate the increased climate impact of air transport, but that it is very likely that the current measures will not be sufficient to support achieving the 1.5-degree Celsius target established in Paris. This is because non-carbon-dioxide effects, particularly the climate-warming effect of condensation trails, have not been taken into account so far. Research findings from the past few years have made it increasingly clear that contrails and nitrogen oxides together have a greater climate impact in air transport than carbon dioxide emissions alone. The results of the study have now been published in the specialist journal Nature.

"Non-carbon-dioxide effects account for the largest share of the climate impact of aviation. At DLR, we are committed to ensuring that these effects are considered. We want to develop comprehensive solutions for the climate-neutral flight of tomorrow that avoids carbon dioxide emissions and non-carbon-dioxide effects," emphasises Markus Fischer, DLR Deputy Board Member Aeronautics.

"In our study, we show that the CORSIA offsetting programme in its current form – that is, without taking non-carbon-dioxide effects into account – will fall short of climate targets aimed at the 1.5-degree Celsius limit between 2025 and 2064, with a probability of 90 percent," says study leader Volker Grewe from the DLR Institute of Atmospheric Physics in Oberpfaffenhofen. "As a group of experts, we believe our results reveal the risk of a discrepancy that could lead to an increasing air-transport-induced greenhouse effect instead of stabilisation." At the 2015 United Nations Climate Change Conference in Paris, the participating states agreed that global warming should be limited to 1.5 degrees compared to pre-industrial levels. As a result, the ICAO and its members adopted the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) programme, which is now being implemented by 88 countries around the world.

Stabilising the climate impact with Flightpath 2050

The research team also looked at the Flightpath 2050 emissions targets presented by the Advisory Council for Aeronautics Research in Europe (ACARE) in 2011 (75 percent reduction in carbon dioxide emissions and 90 percent reduction in nitrogen oxide emissions by 2050 per passenger kilometre and for individual aircraft by 2050, as compared to 2000). "In our assessment, it is highly probable that these targets can indeed stabilise the climate impact of air transport," says Grewe. "However, even the targets of Flightpath 2050, which are more stringent than CORSIA, will also lead to a consistent contribution to global warming by this industry in the 21st century. The reason for this is the further growth in air traffic, which is expected to be significant, coupled with insufficient consideration of non-carbon-dioxide effects. At the time that Flightpath 2050 was formulated, these could not yet be properly incorporated into the setting of targets."

Air transport plays an important role in the global economy. The need for mobility is increasing globally and this will likely lead to significant growth in the air transport industry over the coming decades. The restrictions on air transport caused by the COVID-19 pandemic have been dramatic and continue to have a major impact. "However, the effect on the climate will only be minor if the air transport sector recovers within the next three to 15 years," adds Grewe. "That is why it is important to set out more ambitious climate targets for air transport now."

DLR – research for climate-neutral air transport

The consequences of climate change demand action for climate-neutral air transport. This involves new technologies that will also ensure global mobility in the future. With its 25 institutes and facilities in the field of aeronautics research, DLR is driving this change forward with technologies for sustainable, environmentally compatible flight. Expertise from DLR's research programmes in space, energy and transport will also play an important role in this.

DLR has systems expertise in aeronautics research and sees itself in the role of an architect. DLR’s goal is 'emission-free air transport', in order to achieve the climate targets that have been set. In doing so, the results of research must flow directly into the development of new products.

There is a considerable need for research and development on the path to climate-compatible air transport, which requires continuous funding and support. Much of this needs to be researched at a fundamental level, tested in practice and approved. DLR can do this with large-scale facilities such as its research aircraft, propulsion demonstrators and large-scale computers. In 2020, DLR published the white paper 'Zero Emission Aviation' together with the German Aerospace Industries Association (Bundesverband der Deutschen Luft- und Raumfahrtindustrie; BDLI). DLR is currently working on a Zero Emission strategy

  • Falk Dambowsky
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-3959
    Linder Höhe
    51147 Cologne
  • Prof. Dr. Volker Grewe
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of At­mo­spher­ic Physics
    Münchener Straße 20
    82234 Oberpfaffenhofen


Stay up to date and sub­scribe to the DLR newslet­ter with ar­ti­cles from the DLR ed­i­to­ri­al team in Ger­man and En­glish.

Main menu