Contrail-cirrus clouds, not carbon dioxide, cause half of aviation's total climate impact, yet they remain largely unregulated. The UK government has launched a coordinated research programme to tackle these non-CO2 effects—nitrogen oxides and contrail-cirrus—which together account for two-thirds of aviation's warming. While CO2 from burning jet fuel is well understood, the science behind contrail formation and NOx chemistry is far less certain, leaving a major gap in climate policy. A coordination team will integrate projects across atmospheric science and aeronautical engineering, combining results to answer practical questions: Can airlines realistically avoid creating contrails? What operational changes reduce NOx emissions? How should policymakers weigh these impacts against CO2? If successful, the programme could deliver concrete mitigation options for industry and government, helping the UK meet its net-zero targets. Reducing non-CO2 impacts is a significant lever—one that current regulations largely ignore. The team will also engage international researchers, the Royal Aeronautical Society, and the Jet Zero Council, ensuring UK findings influence global aviation standards. This is applied, policy-facing science aimed at closing a blind spot in climate action.
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The climate impacts of aviation arise in 3 main ways. Carbon dioxide is the inevitable consequence of burning hydrocarbon fuels. Nitrogen oxides (NOx) are formed by the high temperatures in jet engines and subsequently affect the concentrations of the greenhouse gases ozone and methane. Contrails and cirrus are produced following the emission of a range of particle precursors under certain atmospheric conditions. Contrail-cirrus is responsible for half of the overall climate impact of aviation, NOx for a sixth, and CO2 the remaining third. Significant climate wins would result from reducing NOx and contrail-cirrus, the non-CO2impacts from aviation. The UK government has established a research programme on Aviation’s non-CO2 Impacts on the Climate which covers atmospheric and technological projects involving academia and industry and funded through NERC and ATI. The programme focuses on (a) improving our understanding of aviation’s non-CO2 impacts; and (b) identifying and developing mitigating actions to address those impacts. The aims for the Coordination Team in helping meet the programme’s challenges are: a) provide strategic vision to the programme to achieve impactful outcomes; b) support and integrate the funded research projects deliver benefits, mitigation options, informing industry and government decisions; and c) promote engagement with policymakers in government, industry and non-governmental organisations. Added value will be created through hosting online and in-person research discussions, promoting the programme to interested external partners, and working with the Expert Advisory Group to provide advice to the funders through the Programme Board. Core aspects are organising annual meetings and hosting a programme website. Integrative initiatives will provide an extra layer of interpretation through combining results from different projects to answer higher level questions of interest. Examples of such initiatives are the real-world practicality and desirability of contrail mitigation, operational measures to reduce impacts, and policy-facing assessments regarding the non-CO2 impacts. Where appropriate, these activities will be organised in collaboration with other groups, such as the Royal Aeronautical Society, the Jet Zero Council and the Aerospace Growth Partnership. Collaborations with leading international researchers on non-CO2 aviation impacts will be sought to enhance the value derived from the programme. Communication with a broad range of stakeholders, including the public, the media, politicians and other decision-makers will be pursued. The outputs of the additional activities organised through this coordination will be programme reports to the funders, focussed assessments of specific topics, cross-project meetings including the annual meetings and the programme finale which will integrate the programme’s research results and provide information/ guidance to industry and government on how to mitigate the non-CO2 impacts. Given the size of the non-CO2 climate impacts, this could be a major contribution to the UK’s achieving its net-Zero targets as well as being internationally influential. The Coordination Team provides expertise on atmospheric science and broader environmental issues as well as aeronautics and aircraft operations giving a breadth of knowledge. The team’s experience covers academia, ensuring impact from environmental research, industrial aeronautics engineering, the Transport Systems Catapult and operational airline experience. The team is experienced in coordinating research programmes on atmospheric and aeronautic/aviation issues with a focus on the transition to sustainable aviation. The team will provide strategic leadership, develop strong relationships between funded projects, and identify opportunities to provide enhanced value.
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