Environmental impact of aviation

[2] Jet airliners contribute to climate change by emitting carbon dioxide (CO2), the best understood greenhouse gas, and, with less scientific understanding, nitrogen oxides, contrails and particulates.

Aviation's environmental footprint can be reduced by better fuel economy in aircraft, or air traffic control and flight routes can be optimized to lower non-CO2 effects on climate from NOx, particulates or contrails.

[5] While the main greenhouse gas emission from powered aircraft is CO2, jet airliners contribute to climate change in four ways as they fly in the tropopause:[6] In 1999, the IPCC estimated aviation's radiative forcing in 1992 to be 2.7 (2 to 4) times that of CO2 alone − excluding the potential effect of cirrus cloud enhancement.

[1] Uncertainties remain on the NOx–O3–CH4 interactions, aviation-produced contrails formation, the effects of soot aerosols on cirrus clouds and measuring non-CO2 radiative forcing.

[29] As it accounts for a large share of their costs, 28% by 2007, airlines have a strong incentive to lower their fuel consumption, reducing their environmental footprint.

[3] The UK's Department for BEIS calculate a long-haul flight release 102 g of CO2 per passenger kilometre, and 254 g of CO2 equivalent, including non-CO2 greenhouse gas emissions, water vapor etc.

[37] Given that growth projections indicate that aviation will generate 15% of global CO2 emissions, even with the most advanced technology forecast, she estimated that to hold the risks of dangerous climate change to under 50% by 2050 would exceed the entire carbon budget in conventional scenarios.

[39] This prediction is supported by data showing that incidents of severe turbulence increased by 55% between 1979 and 2020, attributed to changes in wind velocity at high altitudes.

Without regulation, global aviation emissions may triple by mid-century and could emit more than 3 Gt of carbon annually under a high-growth, business-as-usual scenario.

[5] Air traffic causes aircraft noise, which disrupts sleep, adversely affects children's school performance and could increase cardiovascular risk for airport neighbours.

[47] Sleep disruption can be reduced by banning or restricting flying at night, but disturbance progressively decreases and legislation differs across countries.

Bottom feeder populations can be reduced or eliminated by low DO levels, changing a community's species profile or altering critical food-web interactions.

[67] A 2024 study published in Communications Earth & Environment revealed that carbon dioxide emissions from private jet travel surged to 15.6 million tonnes in 2023, a 46% increase compared to 2019.

Technological innovation could also mitigate damage to the environment and climate, for example, through the development of electric aircraft, biofuels, and increased fuel efficiency.

[69] To achieve these goals, multiple measures were identified: more fuel-efficient aircraft technology; development and deployment of sustainable aviation fuels (SAFs); improved air traffic management (ATM); market-based measures like emission trading, levies, and carbon offsetting,[69] the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).

"[71] In February 2021, Europe's aviation sector unveiled its Destination 2050 sustainability initiative towards zero CO2 emissions by 2050: while air traffic should grow by 1.4% per year between 2018 and 2050.

[74] The aviation sector could be decarbonized by 2050 with moderate demand growth, continuous efficiency improvements, new short-haul engines, higher SAF production and CO2 removal to compensate for non-CO2 forcing.

[75] With constant air transport demand and aircraft efficiency, decarbonizing aviation would require nearly five times the 2019 worldwide biofuel production, competing with other hard-to-decarbonize sectors, and 0.2 to 3.4 Gt of CO2 removal to compensate for non-CO2 forcing.

[76] Synthetic fuels would need little aircraft modification, but necessitates green hydrogen feedstock and large scale direct CO2 air capture at high costs.

Meanwhile, emerging technologies like e-kerosene, though potentially reducing climate impacts significantly, face economic challenges as they cost nearly seven times more than traditional jet fuel, and the future of 45 proposed power-to-liquids plants in Europe remains uncertain, according to Transport & Environment.

[81] As electric machines and converters are more efficient, their shaft power available is closer to 145 Wh/kg of battery while a gas turbine gives 6,555 Wh/kg of fuel: a 45:1 ratio.

[100] According to a study, the attainment of the 1.5–2 °C global temperature goal necessitates substantial demand reductions in the critical sectors of aviation, shipping, road freight, and industry, should large-scale negative emissions not be realized.

[101] According to the IMAGE model used to project scenarios aimed at limiting global temperature increases to 1.5 °C and 2 °C, it is suggested that achieving deep decarbonization within the aviation sector within the specified timeframe is contingent upon a reduction in air travel in certain markets.

[102] The significant challenges of sustainable aviation fuel expansion, including food security, local community impacts, and land use issues, underscore the importance of simultaneous demand reduction efforts.

[103][104] According to the IPCC Sixth Assessment Report, "the greatest Avoid potential" in demand-side mitigation, which consists of Avoid-Shift-Improve (ASI) options, "comes from reducing long-haul aviation and providing short-distance low-carbon urban infrastructure".

[24] Stefan Gössling of the Western Norway Research Institute estimates 1% of the world population emits half of commercial aviation's CO2, while close to 90% does not fly in a given year.

[121][122] The Centre for Aviation, Transport and Environment at Manchester Metropolitan University estimates the only way to lower emissions is to put a price on carbon and to use market-based measures like the EU ETS.

[85] Their position is that emissions in problematic sectors, like aviation, should be offset by greenhouse gas removal, carbon capture and storage and reforestation.

[141] In 2019, Air France announced it would offset CO2 emissions on its 450 daily domestic flights, that carry 57,000 passengers, from January 2020, through certified projects.

[30] As of September 2020, the Single European Sky has still not been completely achieved, costing 6 billion euros in delays and causing 11.6 million tonnes of excess CO2 emissions.