Emissions from aviation continue to grow but need to fall. There are no technical fixes. Instead we need to curb frequent flying and stop airport expansion.

11 Mar 2021

Emissions from aviation need to fall There are no technical fixes. Instead we need to curb frequent flying and stop airport expansion.


Most people like to travel, and air travel remains a popular form of transport. But greenhouse gases and other emissions from aviation are a growing cause of global warming. There are no easy technical fixes to this problem. Instead, to avoid dangerous climate change we need to act urgently to reduce emissions from flying.

An ambitious emissions reduction target is needed. This will require higher taxes – they should be fair and based on the “polluter pays” principle1.

Facts about aviation

  • Emissions of greenhouse gases from aviation2 are becoming increasingly important. They were 8% of the UK total in 20193, with most being from long-haul international flights4. While relatively small, this proportion was still increasing before the Covid pandemic. Between 1990 and 2019, domestic and international aviation emissions more than doubled5, while overall UK emissions are estimated to have reduced by 45%6. The number of flights dropped substantially in 2020 due to the pandemic, but the Committee on Climate Change (CCC) expects a return to previously projected demand levels from 2024 in most scenarios.7
  • Indirectly acting emissions8. Aviation also produces emissions such as nitrogen oxides (NOx) that indirectly contribute to global warming. The science is uncertain9, but it is estimated that this increases the harm caused by flying by about 70%.10
  • UK aviation was increasing substantially before the Covid 19 pandemic. It grew by over 4% per year between 2014 and 201911. The Department for Transport forecasts that in the absence of airport capacity constraints, aviation would grow from 267 million passengers per annum (mppa) in 2016 to 495 mppa in 2050, an increase of 85%12.
  • Most air travel is for leisure. In 2016, 72% of passengers to/from UK airports were traveling for leisure13. In most cases, more climate-friendly holidays could be taken closer to home.
  • Most flights abroad are taken by a minority of people. UK government statistics for England show that in 2017 just 1% people took 20% of all flights abroad, and 10% of people took 52% of all flights abroad.14 15
  • Unconstrained aviation growth is inconsistent with UK emissions targets. The UK now has a legally binding target of net zero emissions by 2050. Under the CCC’s recommended pathway, passenger numbers would not grow more than 25% above 2018 levels and there would be no net airport expansion16. Friends of the Earth believes that rather than allowing for further increases, passenger numbers need to decrease.
  • Technology developments are not able to keep up with the growth of passenger numbers. Planes are gradually becoming more efficient and will continue to do so17, but not at the pace necessary to allow for unconstrained growth in flights and passenger numbers. This means that aviation needs to be limited.

The problem

Aviation is expected to be responsible for an increasing proportion of greenhouse gas and other emissions to 2050.18 There are no easy solutions. The industry and others are trying to stave off effective measures to constrain emissions by promoting alternative approaches. These alternatives ­­don’t stand up to scrutiny.


The aviation industry is banking on biofuel as a future fuel.19 But this would require industrial-scale cultivation of biomass – things like maize, palm oil or woody crops. It would compete for land with food production and nature protection, as well as risk displacement of local communities. Clearance of forests to make way for plantations can itself lead to massive greenhouse gas emissions. Use of waste and newer biofuel production methods might help, but there’s currently no sustainable way to produce aviation biofuel at scale.

In addition, biofuel use won’t eliminate all climate-warming emissions. For example, reductions in emissions of NOX are small or insignificant.20

Carbon offsetting and CORSIA

In theory, carbon offsetting enables individuals and institutions to pay for environmental projects that reduce carbon emissions with the aim of balancing out their own carbon footprints. But in practice the vast majority of these projects have been shown to be ineffective. In other words, in most cases offsetting doesn’t work21 22. A better response to the environment and climate emergency23 is not to fly. That’s the simple truth.

The International Civil Aviation Organization has nonetheless adopted a carbon offsetting scheme (CORSIA) that will require airlines to buy carbon offsets to compensate for their growth in CO2 emissions.

Even if the principle of offsetting aviation emissions were accepted, CORSIA would be a very poor scheme. It has a weak overall target that allows gross aviation emissions growth, rather than the decrease that the planet needs. It doesn’t cover domestic aviation (or most private aviation24), ignores emissions other than CO2, and its rules fail to ensure it has an effective offset mechanism 25 26 27 28.

The CCC say that CORSIA is not currently compatible with the Paris agreement or the UK’s Net Zero commitment, and that it needs to be strengthened.29 They have recommended against use of international offsets30, and say that under its current rules, CORSIA should not contribute to meeting the carbon budgets.

Aviation Emissions Trading

The UK Emissions Trading Scheme (UK ETS) will set a UK level ‘cap’ at a national level and allocate emissions allowances to individual companies within this overall limit. Companies that exceed their allowances will be able to purchase additional allowances from others that have unused allowances. Friends of the Earth believes that aviation should not be included in emissions trading because, due to aviation’s indirectly acting emissions, a tonne of CO2 from other sectors does not have the same warming potential as a tonne of CO2 from aviation.

However, if aviation is included in the UK ETS, then a multiplier 31should be used to reflect the impact of indirectly acting emissions. Although there is ongoing scientific discussion about the best way to compare CO2 and indirectly acting emissions, this approach would be preferable to ignoring their impacts.


Several innovative solutions are being investigated, including electric and hybrid aircraft, more efficient engines, and use of renewable electricity to produce fuel. This innovation is welcome. It may have a role to play, but none is currently ready on the scale needed, and most will not be readily available for decades.

Reducing indirectly acting emissions at the cost of more CO2

There are potential approaches to dealing with indirectly acting emissions that could result in an increase of CO2 emissions3233.  Friends of the Earth does not support such approaches if the CO2 penalty is significant, because CO2 remains in the atmosphere much longer than indirectly acting emissions.

Non-climate change impacts

Noise and air pollution are also serious problems caused by aviation, as is the impact on nature from airport expansion, although these are not the focus of this short paper.

How we can reduce emissions from aviation

Emissions from aviation must not be allowed to grow. Instead they need to decrease, starting now. The UK government needs to adopt a range of measures, including a tougher emissions target:

Encourage alternatives to air travel

We need to develop alternatives to air travel. For example, long distance train travel (which has much lower emissions per passenger mile), and improved wifi and video-conferencing facilities. The Covid pandemic has shown the potential.

Support development of new technology, but don’t rely on it until it’s ready

New technologies and innovations may bring new solutions in future. But we can rely only on technology that’s known to be workable at large scale and that will be available when we need it. A future possibility of technologies such as synthetic aviation fuels must not reduce the level of mitigation action taken now to reduce aviation emissions over the next few decades.

Encourage institutional responsibility

Businesses and other institutions should be encouraged to limit their use of aviation and to consider the environmental impacts before choosing to fly. A requirement for organisations to report on their air travel should be considered. Individuals should also be encouraged to use alternatives to flying.

Constrain aviation

We need to reduce emissions from air travel. With current aviation technology, that can only mean fewer flights. This will require measures such as a frequent flier levy, removal of tax breaks on aviation fuel, and limiting numbers of flights at airports. Taxes should be fair and based on the polluter pays principle, for example with higher payments for longer distances. The funds raised could be used in many areas (e.g. better public transport, energy efficiency, tree planting, peatland restoration).

Reject airport capacity increases

A number of airports across the UK are seeking to expand. But we need fewer flights and less emissions, not more. In December 2020 the Supreme Court upheld the Government’s decision-making process in deciding to proceed with the third runway at Heathrow but did not rule whether or not the plan was consistent with new net zero legislation. It also said that climate considerations including the net zero carbon reduction target must be considered in full as part of planning.

The CCC has now said that there should be no net expansion of UK airport capacity unless UK aviation is on track to sufficiently outperform its net emissions trajectory and can accommodate the additional demand34. In other words, they tacitly said Heathrow shouldn’t be expanded.

We must stop plans to expand airport capacity, and government must withdraw its support for Heathrow expansion proposals in light of the zero carbon target.

Ensure fairness

A frequent flyer levy would be a step in the right direction. Flying shouldn’t become a luxury reserved for the wealthy. Alternative approaches, such as rationing of flying, may be worthy of exploration.

Reject false solutions and promote a much better international aviation agreement

The UK government should formally reject CORSIA and offsetting. It should also more actively promote an international aviation agreement that reduces aviation, rules out unsustainable use of biofuels, covers all climate-warming emissions, and is consistent with the 1.5°C limit. But it shouldn’t wait for this agreement – it should show international leadership and adopt these measures on its own.

Set tougher UK emissions reduction target(s) for aviation

Aviation needs to play its part in ensuring the UK delivers on the Paris Climate Change Agreement to limit global warming to 1.5°C. Friends of the Earth is calling for an aviation emissions target35 that is more stringent than the 23 million tonnes of CO2 equivalent (MtCO2e) per year in the CCC’s “Balanced Pathway” that is the basis of their recommended carbon budget36. This is because it ignores the indirectly acting emissions mentioned above. This unaccounted factor increases the priority that needs to be given to reducing with aviation emissions.37

While Friends of the Earth’s suggested maximum level is exacting it does not rule out flying altogether. For illustration, using a multiplier of 1.7 (see Note 10) would allow for 13.5 million tonnes of CO2 equivalent (MtCO2e) per year. Taking into account both direct and indirect climate impacts from aviation, and sharing out aviation fairly, this would still allow for every person in the UK today to take just over six return economy class trips to Rome every seven years, or one economy-class return flight to Australia every 14 years38.








  • 1. Polluter pays principle: This is the commonly accepted practice that those who produce pollution should bear the costs of managing it to prevent damage to human health or the environment. See LSE, “What is the polluter pays principle?,” 2018, http://www.lse.ac.uk/GranthamInstitute/faqs/what-is-the-polluter-pays-principle/, accessed 25 January 2021.
  • 2. Greenhouse gas emissions from aviation: These include carbon dioxide (CO2), nitrous oxide (N2O), water vapour, and some methane (CH4). Of these, CO2 has by far the largest effect. Carbon dioxide, methane and nitrous oxide are among a basket of greenhouse gases identified by the Kyoto Protocol, which also includes methane, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6). The UK Climate Change Act of 2008 limits emissions of Kyoto Protocol gases. Water vapour is not a Kyoto Protocol gas, and so isn’t covered by the Act.
  • 3. Proportion of aviation emissions: The CCC reported to Parliament in June 2020 that 8% of UK emissions in 2019 were from aviation. Committee on Climate Change, “Reducing UK emissions - Progress Report to Parliament”, 2020, page 22, https://www.theccc.org.uk/wp-content/uploads/2020/06/Reducing-UK-emissions-Progress-Report-to-Parliament-Committee-on-Cli.._-002-1.pdf, accessed 18 January 2021.
  • 4. Most aviation emissions are from long-haul flights: Committee on Climate Change, “The Sixth Carbon Budget - Aviation”, 2020, page 17, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 3 February 2021.
  • 5. Non-military aviation emissions more than doubled: Emissions from domestic and international aviation in 2018 were 124% above 1990 levels (and were higher in 2019). Military aviation emissions have fallen 71% from 1990 levels. Committee on Climate Change, “The Sixth Carbon Budget - Aviation”, 2020, page 7, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 25 January 2021.
  • 6. Overall UK emissions reduced by 45%: Provisional government figures show that in 2019, total UK greenhouse gas emissions were 45.2% lower than in 1990. Department for Business, Energy & Industrial Strategy, “2019 UK greenhouse gas emissions, provisional figures – statistical release”, 2020, page 1, https://www.gov.uk/government/statistics/provisional-uk-greenhouse-gas-emissions-national-statistics-2019, accessed 21 January 2021.
  • 7. Aviation expected to return to pre-Covid 19 levels: The CCC estimates a drop in 2020 of 61% in UK flights and emissions due to Covid 19, and a return to previously projected levels from 2024 in most of its scenarios. For two of the CCC scenarios, ‘Widespread Engagement’ and ‘Tailwinds’, it estimates a return to 90% of previously projected levels. Committee on Climate Change, “The Sixth Carbon Budget - Aviation”, 2020, page 16, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed on 21 January 2021.
  • 8. Indirectly acting emissions: In addition to carbon dioxide, aviation also produces “non-CO2” emissions, including other greenhouse gases and gases that indirectly lead to warming or cooling. For example, nitrogen oxides (NOx) lead to the formation of ozone (O3) which has a warming effect, and a reduction in atmospheric methane with a resulting cooling effect. Overall, these two opposing effects result in a net warming from NOx. Other indirectly acting emissions from aviation include water, sulphur oxides, hydrocarbons and soot, and lead to the generation of aerosols, contrails, and clouds (“induced cirrus cloudiness”). Sulphate aerosol is thought to have a small cooling effect, but overall the non-CO2 effects are warming. See Lee et al., ”The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018”, Atmospheric Environment, Volume 244 (published online 2020), https://www.sciencedirect.com/science/article/pii/S1352231020305689?via%3Dihub, accessed 21 January 2021. See also CarbonBrief, “Explainer: The challenge of tackling aviation’s non-CO2 emissions”, 2017, https://www.carbonbrief.org/explainer-challenge-tackling-aviations-non-co2-emissions, accessed 21 January 2021).
  • 9. Uncertainty in scale of effects of indirectly acting emissions: See Figure 3 in the Atmospheric Environment paper mentioned in note 8. The very large error bars for the radiative forcing associated with various emissions illustrate the uncertainty. The report also highlights the range of metrics and timescales that can be used to determine ‘CO2-emission equivalences’ for non-CO2 emissions.
  • 10. Multiplier for non-CO2 effects: When accounting for the impacts of greenhouse gases, ‘multipliers’ are often used to reflect the different impacts of different gases relative to CO2. A gas with the same impact as CO2 has a multiplier of 1. A gas with a higher impact (such as methane) has a multiplier larger than 1. Impact is typically measured using Global Warming Potential (GWP). There are alternative metrics; for example Global Temperature Potential (GTP) and GWP*. These metrics have timescales – GWP100 reflects warming over a period of 100 years. The current international norm under the Paris Agreement is to use GWP100 as the primary metric. Although there is ongoing scientific uncertainty over the application of this to indirectly acting emissions, Friends of the Earth accepts that it is the best metric to use until scientific advice changes. Uncertainty over the best metric must not be a reason to hold back from action, including specific policy measures on shorter-life non-CO2 emissions. The CCC says identification of a multiplier remains “extremely challenging”. A UK government methodology for company reporting of emissions recommends a multiplier of 1.9 as a central estimate, based on an estimate of the GWP100 metric. Since publication of that paper, new scientific research has been published that estimates a value of 1.7 for GWP100. See a) page 374 of Committee on Climate Change, “The Sixth Carbon Budget - The UK’s path to Net Zero”, 2020, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 21 January 2021), b) page 88 of Department for Business, Energy and Industrial Strategy, “2020 government GHG conversion factors for company reporting, Methodology paper for emission factors: final report”, 2020, https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2020, accessed 21 January 2021, c) Table 5 (last row) of Lee et al., ”The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018”, Atmospheric Environment, Volume 244 (published online 2020), https://www.sciencedirect.com/science/article/pii/S1352231020305689?via%3Dihub, accessed 21 January 2021.
  • 11. Growth of UK aviation: Numbers of passengers at UK airport terminals grew by 24.5% between 2014 and 2019. This equates to 4.5% per annum. See CAA airport data 2019, Table 10.3, https://www.caa.co.uk/Data-and-analysis/UK-aviation-market/Airports/Datasets/UK-Airport-data/Airport-data-2019/, accessed 21 January 2021.
  • 12. Forecast without airport growth constraints: The Department for Transport (DfT) forecast of 85% growth between 2016 and 2050 equates to about 1.8% per year. See pages 9-11 of Department for Transport, “UK aviation forecasts 2017”, https://www.gov.uk/government/publications/uk-aviation-forecasts-2017, accessed 21 January 2021.
  • 13. Most aviation is for leisure: In 2016, 19% of passengers starting or ending their journeys at UK airports were flying for business. Along with the 72% flying for leisure purposes, this accounts for 91% of passengers. The remaining 9% of passengers were making international transfers. See p60 of Department for Transport, “UK aviation forecasts”, 2017, https://www.gov.uk/government/publications/uk-aviation-forecasts-2017, accessed on 25 January 2021).
  • 14. Most flights abroad are made by relatively few people: The 1% and 10% figures are based on National Travel Survey data for England. See table NTSQ08004 at https://www.gov.uk/government/statistical-data-sets/ad-hoc-national-travel-survey-analysis#flights (accessed 21 January 2021)
  • 15. People who fly more tend to have higher incomes: In 2016, the DfT found that “The proportion of people who took at least one international flight in the last 12 months increased with household income level, from 30% in the lowest quintile to 70% in the highest.” See page 26 of Department for Transport, “National Travel Survey: 2016 report”, https://www.gov.uk/government/statistics/national-travel-survey-2016, accessed on 21 January 2021).
  • 16. Unconstrained aviation growth is inconsistent with UK targets: The CCC’s recommended Balanced Scenario limits aviation growth to 25% above 2018 levels. This allows for 365 million passengers per year in 2050. This is within the current airport capacity of at least 370 million passengers. Committee on Climate Change, “The Sixth Carbon Budget - Aviation”, 2020, pages 10 and 11, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 25 January 2021.
  • 17. Technology improvements to reduce emissions: The CCC and DfT commissioned a project to review the potential for reducing aviation emissions, which considered improvements in a range of areas including engines, aircraft design, airline operations (e.g. aircraft speeds), and air traffic management (e.g. optimal routing). The key finding was that by 2050 there’s potential to reduce aviation emissions by up to around 40% versus a comparable year 2000 aircraft. See page 172 of Committee on Climate Change, “Net Zero Technical report”, 2019, https://www.theccc.org.uk/publication/net-zero-technical-report/, accessed 21 January 2021).
  • 18. Aviation’s increasing share of emissions: There was a large fall in aviation traffic following the outbreak of the Covid 19 pandemic. However, the CCC’s projection for its central ‘Balanced Scenario’ indicates that over the period to 2050, while emissions from other sectors are expected to reduce substantially, emissions from aviation will fall more slowly and so take an increasing proportion of the total. See Committee on Climate Change, “The Sixth Carbon Budget - The UK’s path to Net Zero ”, 2020, page 66, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 21 January 2021.
  • 19. Banking on biofuels: The airline industry association (IATA) says that “In the medium term, SAF [Sustainable Aviation Fuels] will be the only energy solution to mitigate the emissions growth of the industry”. The term “Sustainable Aviation Fuels” includes advanced biofuels. Although SAF can also be produced through non biological means (e.g. power to liquid), none of these can currently operate at scale. See International Air Transport Association, “Sustainable Aviation Fuels Fact sheet”, May 2019, https://www.iata.org/en/programs/environment/sustainable-aviation-fuels/#tab-2, accessed on 21 January 2021.
  • 20. Biofuels do not eliminate all climate warming emissions: Tests have shown that biofuels don’t eliminate all climate-warming emissions. A US Federal Aviation Authority report compared conventional fuels (Jet A and JP-8) with a biofuel / conventional fuel blend (50% synthetic kerosene with aromatics / 50% JP-8). It found that the emissions of nitrogen oxides (NOx) with the biofuel / conventional fuel blend were similar to those from the conventional fuels. See figure 8-4 in Pratt and Whitney, “Swedish Biofuel Performance Evaluation”, Federal Aviation Authority, 2016, https://www.faa.gov/about/office_org/headquarters_offices/apl/research/aircraft_technology/cleen/reports/, accessed 21 January 2021. See also sections 2.5 and 2.6 in International Coordinating Council of Aerospace Industries Associations , “Impact of Alternative Fuels On Aircraft Engine Emissions”, International Civil Aviation Organization (ICAO), 2009, https://www.icao.int/Meetings/caaf2009/Documents/CAAF-09_IP011_en.pdf, accessed 21 January 2021.
  • 21. Offsetting is inadequate for aviation: Offsetting is inadequate as a way to manage UK aviation emissions. Key reasons for this include that very few offsetting cases work and that most UK aviation is avoidable, for example the majority is for leisure purposes. The very small number of genuine offsetting projects need to be reserved for unavoidable emissions, like the use of gas for home heating. Until heating has been decarbonised (e.g., by the roll out of heat pumps), asking people not to heat their homes would cause real hardship. See also note 26.
  • 22. Voluntarily offsetting: A small amount of flying can’t reasonably be avoided. For these flights responsible institutions and individuals may want to voluntarily purchase offsets for the resulting emissions. Friends of the Earth does not have details on which offset projects are genuine, however WWF has worked with others to identify “gold standard projects”. Such voluntary offset schemes may be helpful if used responsibly, but they’re no substitute for robust measures put in place by government to reduce emissions from aviation.
  • 23. Environment and climate emergency: A motion to declare an environment and climate emergency was passed, without a vote, by the UK House of Commons on 1 May 2019. See https://www.parliament.uk/business/news/2019/may/mps-debate-the-environment-and-climate-change/, accessed 25 January 2021.
  • 24. Private aviation: This paper focuses primarily on commercial aviation. However, note that most private jets are excluded from CORSIA. See The Economist, “Plane stupid: Private jets receive ludicrous tax breaks that hurt the environment”, 7 March 2019, https://www.economist.com/leaders/2019/03/07/private-jets-receive-ludicrous-tax-breaks-that-hurt-the-environment,  accessed 21 January 2021. See also Avionics International, “Many Operators Exempt From Upcoming ICAO Carbon Requirements”, 2018, https://www.aviationtoday.com/2018/01/16/many-operators-exempt-upcoming-corsia-requirements/, accessed 21 January 2021).
  • 25. Additionality is problematic: In order to work, offset projects must be “additional” – they wouldn’t have happened anyway. Establishing this is inherently problematic and has been wittily summarised by Dan Welch as follows: “Offsets are an imaginary commodity created by deducting what you hope happens from what you guess would have happened." Or putting it another way: “The key difficulty is that the baseline scenario is a hypothetical scenario; by definition it describes another reality, one in which the activity is not implemented as an offset project”. See United Nations, “Beyond Carbon Markets”, https://www.un.org/en/chronicle/article/beyond-carbon-markets, accessed 21 January 2021. See also page 18 of Anja Kollmuss et al., “Making Sense of the Voluntary Carbon Market - A Comparison of Carbon Offset Standards Carbon Offset Standards”, WWF, 2008, https://www.wwf.de/fileadmin/fm-wwf/Publikationen-PDF/A_Comparison_of_Carbon_Offset_Standards_lang.pdf, accessed 21 January 2021.
  • 26. In practice much offsetting has been ineffective: Many CORSIA offsets are likely to be based on the United Nations’ Clean Development Mechanism (CDM). Evidence shows that such offsetting often doesn’t work in practice. In 2016, a report for the European Commission found that only 2% of projects under the CDM had a high likelihood of being effective. The report also says “Our analysis suggests that the CDM still has fundamental flaws in terms of overall environmental integrity. It is likely that the large majority of the projects registered and CERs [offset credits] issued under the CDM are not providing real, measurable and additional emission reductions.” See Cames et al, “How additional is the clean development mechanism?”, European Commission, 2016, https://ec.europa.eu/clima/sites/clima/files/ets/docs/clean_dev_mechanism_en.pdf, accessed 21 January 2021).
  • 27. Offsetting needs robust eligibility criteria: In addition to the European Commission report mentioned in the previous note, a Nature Climate Change paper found that “If the scheme [CORSIA] allows airline operators the unlimited use of offset credits from already implemented [offset] projects, it will result in no notable emissions reductions beyond those that would occur anyway…” The paper recommends limiting eligibility for offsetting to new projects or projects that are at risk of discontinuing greenhouse gas abatement without further support. See Warnecke et al. “Robust eligibility criteria essential for new global scheme to offset aviation emissions”, Nature Climate Change, 9: 218–221, 2019, https://www.nature.com/articles/s41558-019-0415-y, accessed 25 January 2021).
  • 28. CORSIA rules do not ensure an effective offset mechanism: In early 2020 ICAO’s governing Council approved the first offset programmes to provide emissions units in the 2021-2023 pilot phase of CORSIA. The approval was based on recommendations from ICAO’s Technical Advisory Body (TAB). It was subject to a ‘vintage’ timeframe restriction that may help to avoid some double counting that could occur from 2021, when countries’ own obligations under the Paris Agreement start. However, substantial concerns remain. The TAB report itself (page 17) points out that some programmes only partially demonstrate consistency with the additionality requirement, for example, “by waiving the requirement in circumstances where environmental laws and regulations are not widely observed and/or enforced”. The report also points out concerns in relation to the approach to sustainable development and social safeguards criteria (e.g. see pages 4 and 18). In the case of additionality, the report explains that the TAB took the view that programmes should nonetheless be deemed eligible during the CORSIA pilot, saying “… given that the [eligibility criteria] were only finalized in 2019, programmes and their stakeholders would benefit from more time to familiarize themselves with the criterion and its implications. Thus TAB agreed that such programmes should nevertheless be deemed eligible during the pilot phase, in order to allow time for these further considerations, as applicable”. See Technical Advisory Body (TAB), “Recommendations on CORSIA eligible emissions units”, January 2020, https://www.icao.int/environmental-protection/CORSIA/Documents/TAB/Excerpt_TAB_Report_Jan_2020_final.pdf For background on the approval of offset programmes for CORSIA and the responses to it see GREENAIR, “ICAO Council follows advisory body recommendations and approves CORSIA-eligible carbon programmes”, March 2020, https://www.greenaironline.com/news.php?viewStory=2679, accessed 3 February 2021 and Redshaw Advisors Ltd., “CORSIA offset eligibility explainer”, July 2020, https://redshawadvisors.com/corsia-offset-eligibility-explainer/, accessed 3 February 2021
  • 29. CORSIA is not currently compatible Paris agreement: The CCC says that the current level of ambition under CORSIA is an insufficient contribution to the goals of the Paris Agreement, and that in order for operation of CORSIA to be compatible with the UK’s Net Zero commitment there would need to be appropriate governance for offset credits and sustainable fuels, as well as an appropriate cap. It also says that the credits used to offset emissions would need to lead to genuine and verifiable emissions reductions or removals that are additional to what would have occurred otherwise. See Committee on Climate Change, Committee on Climate Change, “The Sixth Carbon Budget”, 2020, page 425, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 21 January 2021.
  • 30. Non use of international offsets: The CCC’s recommended sixth carbon budget (which includes aviation) advises that the budget should be achieved without the use of international offset credits, including CORSIA offsets. Specifically, it says “Under current rules, credits under CORSIA should not contribute to meeting the carbon budgets. See Committee on Climate Change, “The Sixth Carbon Budget”, 2020, pages 13, 424 and 425, https://www.theccc.org.uk/publication/sixth-carbon-budget/ accessed 27 January 2021. See also Committee on Climate Change, “Net Zero - The UK's contribution to stopping global warming”, 2019, page 21, https://www.theccc.org.uk/publication/net-zero-the-uks-contribution-to-stopping-global-warming/, accessed on 21 January 2021, and Lord Deben, Letter to Secretary of State for Transport, “Net-zero and the approach to international aviation and shipping emissions”, 2019, https://www.theccc.org.uk/publication/letter-international-aviation-and-shipping/, accessed 27 January 2021.
  • 31. See Note 10.
  • 32. Aromatics: Aromatics in fuel leads to soot particles that have a small direct and large indirect effect. There is a sweet spot of just the right amount of aromatics. In theory aromatics can be removed from fossil fuel but at an energy and carbon dioxide penalty (until hydrogen from electrolysis is readily available) and therefore removal is not a good option. Biofuels (which are limited in availability) and synthetic fuel (from direct air capture, and currently extraordinarily expensive) don’t suffer from the excess aromatics problem (in fact some aromatics will need to be added).
  • 33. Impact of indirectly acting emissions is variable: The impact of indirectly acting emissions is highly dependent on the location, season and time of day of the emissions. Therefore, adjusting the times and seasons when flights are taken could cut their indirectly acting emissions significantly. See CarbonBrief, “Explainer: The challenge of tackling aviation’s non-CO2 emissions”, 2017, https://www.carbonbrief.org/explainer-challenge-tackling-aviations-non-co2-emissions, accessed 21 January 2021.
  • 34. No airport expansion: See Committee on Climate Change, “The Sixth Carbon Budget - Aviation”, 2020, page 29, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 21 January 2021.
  • 35. Friends of the Earth’s aviation emission target: Our target is to reduce UK aviation emissions (including non-CO2 emissions) by 2045 to a level that is expected to have the same long term (100 years) warming effect as 23 MtCO2 per year. The actual emission level(s) should be set according to the best scientific understanding. They should be reviewed from time to time as scientific understanding progresses and may be varied accordingly. This approach ensures that indirectly acting non-CO2 emissions are covered by the target, but also recognises that adjustments may be needed as scientific understanding progresses.
  • 36. Carbon budget for aviation in balanced pathway: See Committee on Climate Change, “The Sixth Carbon Budget - The UK’s path to Net Zero ”, 2020, page 176, https://www.theccc.org.uk/publication/sixth-carbon-budget/, accessed 21 January 2021.
  • 37. Prioritise reducing CO2 from aviation: Due to unaccounted non-CO2 effects, reducing CO2 from aviation is likely to provide greater climate benefit than is currently measured by GHG accounting methodologies. Reducing emissions from aviation should be prioritised accordingly. As the science develops, non-CO2 effects should be reflected in carbon budgets and the UK’s Net Zero target.
  • 38. Aviation within Friends of the Earth’s target: These illustrative trips were produced using a carbon footprint calculator, along with a multiplier of 1.7 (see Note 5) to account for non-CO2 emissions. The population of the UK is taken as 67.9 million (Wikipedia). Business class flying is more carbon intensive, and so the figures would need to be modified accordingly. The calculator is available from Carbon Footprint Ltd, https://www.carbonfootprint.com/calculator.aspx, accessed on 21 January 2021).
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Climate change