Dr Lois Pennington, Professor Alice Larkin, and Dr Gaurav Gharde (The University of Manchester)                            AECN0027

Written Evidence Submitted by Dr Lois Pennington, Professor Alice Larkin, and Dr Gaurav Gharde (The University of Manchester)

Call for Evidence: Airport expansion and climate and nature targets

The Tyndall Centre for Climate Change Research is an internationally recognised climate-change research group, bringing together natural scientists, economists, engineers and social scientists to develop sustainable responses to climate change.

This submission is by researchers from Tyndall Manchester based at The University of Manchester. Our work focuses on climate mitigation, with expertise in aviation emissions, sustainable fuels, equity, and carbon budgets. All the views in this submission are attributed to the named authors and do not necessarily reflect those of the wider Tyndall Centre or The University of Manchester. This submission has been supported by Policy@Manchester. The authors would be willing to provide oral evidence, if requested.

The research activities contributing to this work have received support from EPSRC through the Climate Emergency Doctoral Training Programme, The University of Manchester internal support, and EPSRC support for maritime decarbonisation research.

Executive Summary

Current government support for aviation expansion is incompatible with the UK’s legally binding climate commitments. While the inclusion of international aviation emissions in the Sixth Carbon Budget is essential for honest carbon accounting, it also reveals a major gap: the lack of effective measures to reduce emissions from the sector.

The submission recommends that demand management is treated not as a last resort, but as a necessary and equitable policy approach. A formal moratorium on airport expansion is recommended as a proportionate and necessary policy safeguard, alongside other policies such as the introduction of frequent flyer levies.

We also recommend robust sustainability evaluations, including assessments of non-CO₂ effects, feedstock competition, and SAF lifecycle impacts. Regular independent review and oversight is essential, with clear policies that prioritise absolute emissions reductions and procedural fairness.

Without these steps, the UK risks undermining its statutory carbon budgets and falling short of its commitments under the Paris Agreement.

Submission

Question 1

International non-statutory obligations

• The Paris Climate Agreement is the overarching international obligation within which UK aviation policy must operate. As a signatory to this treaty, the UK has committed to aim to hold increases in global mean surface temperature to well below 2°C above pre-industrial levels by 2100, and to pursue efforts to limit this increase to 1.5°C.

• Although not directly enshrined in UK law, these commitments shape the UK’s domestic climate legislation and policy. The Agreement also states that it will be implemented to reflect equity and the principle of common but differentiated responsibilities and respective capacities, in the light of different national circumstances.

• It should be noted, however, that the current Nationally Determined Contribution (NDC) for the UK does not align with the 1.5C goal of the Paris Climate Agreement, as (i) the carbon budget adopted within the NDC is larger than the latest scientific understanding of a ‘1.5C aligned’ budget, and (ii) allocates a much larger share of the global budget to the UK than would be an ‘equitable’ share.

• International aviation falls outside national jurisdiction, and as such the management and regulation of these emissions falls to the International Civil Aviation Organisation, a specialised UN agency. However, at present, there are no statutory or mandated standards for these international emissions – neither CO2, nor the non-CO2[1] warming emissions released by the international aviation sector. As such, whilst there are voluntary mechanisms to manage emissions and incentivise alternative fuels, other measures are needed to align the UK’s contribution to international air travel with the goals of this international treaty. These measures should include a formal cap on aviation emissions, stronger lifecycle sustainability criteria for alternative fuels, the integration of non-CO₂ effects into policy and accounting frameworks, and the use of demand management measures such as frequent flyer levies or caps on airport capacity.

• Domestic aviation emissions, however, are included within the Paris Agreement in the UK’s NDCs.

National Statutory Obligations

• The Climate Change Act is the primary domestic legal framework for addressing the UK’s contribution to climate change. It establishes legally binding targets to achieve net zero greenhouse gas emissions by 2050 and creates a series of five-year carbon budgets with interim targets for emissions reductions. The Act requires the UK Government to develop policies that meet targets across all sectors, and to set legally enforceable carbon budgets. As mentioned, domestic aviation emissions are currently included in these budgets, and international aviation emissions will be formally incorporated into the Sixth Carbon Budget (2033-2038).

• The existing legally binding carbon budgets are published under Carbon Budget Order 2011 (2023-2028), 2016 (2028-2032), and 2021 (2033-2038).

• The UK Emissions Trading Scheme (UK ETS) is a mandatory carbon market that applies to energy-intensive industries, power, and aviation. All aircraft operators conducting routes including UK domestic flights, flights between the UK and Gibraltar, and flights departing the UK to European Economic Area states are required to monitor emissions and cover the cost of any emissions above their free allowance.

• The Sustainable Aviation Fuel (SAF) Mandate sets legally enforceable targets for suppliers of aviation fuel to include increasing amounts of SAF in their fuel mix. The phrasing of the Mandate is given in percentage of the fuel mix, starting at 2% in 2025 and increasing to 10% in 2035, and 22% in 2040. Increasing airport capacity will lead to an increase in the UK’s aviation fuel consumption, and in turn an increase in the volume of SAF that suppliers must provide. Planned UK SAF production sites will generate only half the UK’s 2030 target of 1.2 million tonnes, leading to a reliance on imports when the rest of the world is also undergoing its own decarbonisation challenges.

• The Environment Act 2021 sets statutory targets for air quality, biodiversity, water quality, and waste reduction. Airport development must show compliance with these targets, particularly regarding air quality impacts and biodiversity protection.

• The Air Quality Standards Regulation 2010 sets legal limits on air pollutants, including nitrogen dioxide and particulate matter. Any airport expansion must demonstrate compliance with these limits.

Question 2

• Including international aviation emissions within the Sixth Carbon Budget and subsequent budgets is a necessary step. It provides a more accurate and complete picture of the UK’s overall carbon footprint, and the part played by the aviation sector. However, without significant additional measures to tackle reducing aviation emissions, particularly those focused on curbing demand such as a frequent flyer levy or limits on airport capacity, their inclusion will severely challenge the UK’s ability to meet its climate commitments.

• The scale of the challenge is significant. In the “balanced pathway” in the Climate Change Committee’s (CCC) Sixth Carbon Budget, cumulative aviation emissions are projected to account for approximately 742 MtCO2 between 2025 and 2050, with international aviation responsible for 97% of that total. By 2050, aviation is projected to account for 69% of UK CO2 emissions (not accounting for the effects of non-CO2 warming). This is up from 10% in 2025, as other sectors decarbonise faster. Including international aviation within the carbon budget places the challenge squarely in the UK’s responsibility to address.

• There has been limited progress to develop effective emission reduction mechanisms in aviation. Rather than cutting emissions directly, the sector has thus far relied heavily on offsetting mechanisms, effectively “offshoring” its responsibility to reduce emissions due to a lack of readily available technical solutions.

• Technological solutions cannot deliver necessary reductions quickly enough. Given it is cumulative emissions that count when it comes to greenhouse gas emissions, the pace of energy efficiency improvements and rollout of low carbon solutions remains insufficient to compensate for growth, resulting in growing absolute emissions. These limitations are reflected in the Government’s own CCC projections, which foresees that without demand management measures there will be almost no reductions in aviation CO2 emissions by 2050. This expectation stands in stark contrast compared to other sectors. For example, agriculture and land use (which face their own decarbonisation challenges) are expected to reduce their emissions by 43% by 2050.

• Meanwhile, the urgency of emissions reductions grows. Recent Met Office analysis indicated that limiting warming to 1.5C would require approximately 20% year-on-year cuts in global emissions. For the 2°C target, we need approximately a 7% annual reduction in global emissions, while also accounting for increases in agriculture and provisions for a growing global population.

• Delaying reductions in aviation emissions leads to more carbon entering the atmosphere, greater long term climate impacts, and makes it increasingly difficult to stay within carbon budgets. The CCC’s balanced pathway recognises this, estimating that by 2050, 54% of reductions in aviation would need to come from demand management rather than technological solutions. This need therefore stands in opposition to the expansion of UK aviation capacity.

• From an equity perspective, developed countries like the UK have a responsibility to lead emissions reductions faster than developing countries, given their historical contributions and greater capacity to act. This responsibility extends to international aviation, which has a disproportionately high carbon footprint per capita for wealthier nations’ travellers as aviation disproportionately services a minority of the global population. An estimated 1% of the global population produces 50% of the CO2 from air travel, and national surveys highlight that those who travel by air are disproportionately wealthy.

• In conclusion, while including aviation emissions in carbon budgets is necessary for honest accounting, it brings the responsibility of implementing effective measures to reduce these emissions. Without strong policies to manage aviation demand, including limits on airport capacity, frequent flyer levies, and the removal of tax exemptions on jet fuel, the inclusion of international aviation in the national carbon budgets will make it extremely difficult for the UK to meet its climate commitments. Supporting aviation and airport expansion plans is incompatible with this responsibility, and the UK’s legally binding carbon budgets.

Question 3

• It is important to acknowledge that the emissions targets set out in the CCC’s Carbon Budget 6 and 7 are insufficient to achieve the 1.5C temperature goals enshrined in the Paris Agreement.

• To meet the CB7 emissions targets, the UK will need to reduce total emissions by 75%, compared to 2023 figures. Government policy on airport expansion will have a major impact on the ability to deliver these reductions. If airport capacity is increased, this enables additional demand which existing models do not expect can be sufficiently offset by emissions savings from SAF or efficiency improvements in the timeframe of the Sixth Carbon Budget. The CCC has also advised that no additional airport expansion should occur unless the aviation sector is significantly outperforming expected emissions reductions; a condition that is not currently being met.

• SAF is at a very early stage of implementation, feedstock availability is limited and there is a wide variation in lifecycle emission savings. Burning SAF still generates CO2, and its use at scale still implies substantial emissions. Importantly, non-CO2 effects such as contrails have been found to generate more warming than CO2 emissions, through radiative forcing. SAF does not prevent the formation of contrails, and the actual climate benefit of SAF may be much less than estimated.

• Efficiency improvements in aircraft and operations have been incremental. The rate of improvement in carbon intensity (emissions per passenger-kilometre) is on average 1.5% per year, which has not kept pace with demand growth of 3.6% year on year. This makes airport expansion a critical policy lever. Expanding airport capacity facilitates increased demand, and locks in emissions for decades to come. It also sends a clear signal of expected growth in a sector that already accounts for a growing and inequitable share of emissions.

• Constraining airport operations to existing infrastructure is a necessary and proportionate step. Without this constraint, there is an almost definite certainty that aviation emissions (both CO2 and non-CO2) will undermine the UK’s contribution to climate goals.

Question 4

• Demand projections for UK airports have typically forecast continued growth in both passenger and freight traffic, through to 2050. Current expansion proposals across multiple English airports are based on these projected increases. However, projections for aviation demand are not neutral forecasts; they are influenced by policy decisions that shape and stimulate demand.

• Evidence has long highlighted how airport expansion can create demand, rather than simply responding to it. We would therefore argue that it is misleading to justify expansion solely on the basis of projected growth. Instead, policy should actively shape demand as well as delivering supply side change. This could include measures such as maintaining limits on airport capacity, introducing a frequent flyer levy, reforming Air Passenger Duty (APD) to better reflect environmental costs and equity, and removing the longstanding tax exemption on jet fuel. In parallel, investment in and promotion of domestic tourism could provide viable alternatives, supporting local economies while reducing the need for carbon-intensive international travel.

Question 5

• Projected growth in aviation activity will have major implications for the climate and environment, particularly given the sector’s slow decarbonisation trajectory. The CCC’s Sixth Carbon Budget suggests that, even with modest demand limitation, aviation will become one of the largest sources of UK emissions by 2050.

• Given the significant challenges of decarbonising aviation supply side compared to other sectors, managing demand must be central to aviation policies. It is important that good climate outcomes are put at the heart of decision making, given the repercussions for the environment, economy and wider societal sustainability of not doing so. 

Question 6

• Technological innovations in aviation thus far face delays in implementation, and limitations in their contribution to decarbonisation within the relevant timeframe of the Paris Agreement.

• SAF offers a near-term option that can be used in existing aircraft engines, when blended with fossil fuel, but current supply remains both expensive and extremely limited as production feedstocks face competition from other sectors including heat, energy, and other transport. Most SAF is currently produced from used cooking oil, and the Royal Society has estimated that even if 80% of the UK’s used cooking oil supply was repurposed for jet fuel, it would still only fuel 0.6% of flights. While the UK may rely on imports to make up the difference, recent reports have highlighted the potential sustainability impact of that reliance as some imported biofuels have been found to fraudulently contain undeclared virgin palm oil, a fuel associated with heavy deforestation. As previously mentioned, there is also uncertainty regarding the impact of SAF on non-CO2 emissions that requires further research.

• Hydrogen and electric aircraft may offer longer term options, however neither are likely to contribute significantly before 2050. Hydrogen planes require entirely new engine design and changes to airport infrastructure, while electric aircraft are likely to remain limited to only small regional planes and therefore a very small share of total aviation activity. Overall, these technologies are unlikely to scale in time to meaningfully impact the sector’s emissions within the current carbon budget periods.

• Changes to airport operations may generate some efficiency gains such as improved air traffic control, ground operations, and routing. However, these changes will have only a marginal impact on total emissions, which overwhelmingly is caused by jet fuel combustion.

• Relying on carbon removals, or offsets, to meet net zero poses a major risk. Carbon capture and storage is a nascent technology, with many risks around scalability and effectiveness. If these technologies do not perform as hoped, they will have enabled a delay in action and result in greater long-term harm. Removals should be reserved for residual emissions that are genuinely unavoidable, rather than used to justify continued growth in aviation emissions. The priority should be to reduce emissions at source, particularly in a sector where decarbonisation is particularly challenging.

Question 10

• The Government should ensure that any ANPS revision contains a full investigation of climate, environmental and social sustainability impacts. For climate this should explicitly include both CO2 and non-CO2 effects, and their compatibility with carbon budgets.

• This should go beyond cost-benefit analysis approaches, and include tests for alignment with the Paris Agreement, for long-term climate resilience, and feasibility of decarbonisation measures. It should also account for equity, considering the disproportionate contribution of frequent flyers to emissions and the potential local environmental effects of expansion.

• In relation to alternative fuels such as SAF, there is the potential to target routes and times that are especially vulnerable to non-CO2 effects such as contrail formation (which is affected by things such as temperature and humidity).  Therefore, any appraisal should consider not only how much SAF is used, but how and where, and whether this can affect the overall climate impact of aviation.

• Finally, the sustainability appraisal should include meaningful public participation, particularly from communities most affected by the impacts of potential airport expansion. Procedural fairness is essential to ensure that decisions are transparent, inclusive, and reflect the full range of environmental and social considerations.

Question 11

• Airport and aviation policy should be subject to regular and transparent reviews, to ensure climate and environmental obligations are being met. This review must include annual reporting against emissions targets. This should be supported by formal independent oversight, such as an expanded role for the CCC or a strengthened Jet Zero Taskforce, to provide regular, evidence-based progress.

• The review process should be transparent about the limits of technological solutions in the required timeframes and base its strategies on the latest scientific evidence. Demand management strategies should be recognised as a and necessary policy tool with benefits for wider society, not a last resort.

• Oversight committees such as the Jet Zero Taskforce should maintain and strengthen the range of academic and civil society voices participating to ensure independent, evidence-led input.

Question 12

• Ministers should offer a range of policy safeguards to ensure that domestic and international aviation is aligned with climate and environmental targets. These measures should cover demand and supply side measures, and be grounded in principles of equity, science, and long-term sustainability.

• Ministers must commit to clear policies that prioritise absolute emissions reductions. A key safeguard includes embedding demand management within aviation policy, not as a last resort but as a core strategy alongside supply-side measures. While demand management may be treated as potentially difficult, there is growing public support for fair and targeted measures. This is particularly relevant given that long haul flights, which drive a significant share of emissions, are taken by a small and relatively affluent minority. Public acceptability can be strengthened by fairness, including safeguards such as frequent flyer levies.

• On the supply side, safeguards should include the strategic targeting of SAF to where it can deliver the greatest benefit in emissions reductions. SAF sustainability assessments should also consider potential alternative uses for the feedstock, ensuring that it results in the best environmental outcome. 

• On a strategic level, aviation policy must be assessed against a Paris-aligned pathway. Annual efficiency and carbon intensity improvements must consistently and substantially outpace any growth in demand. Without these safeguards, there is a high risk that the UK’s aviation policy will lead it to miss its statutory climate commitments.

              April 2025