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Scenario Modelling Tool

Designing a scenario-modelling tool to inform policy on air pollutant emissions

Designing a scenario-modelling tool to inform policy on air pollutant emissions

Ricardo’s experts develop a modelling tool to support UK Government decision makers in the development of policy to meet obligations under the European Commission’s National Emission Ceilings Directive and UK Clean Air Strategy targets.

‘The diverse skills of our team enabled us to create a scientifically robust, intuitive and technologically secure evidence platform for Defra to investigate the future impacts of policies and technologies on air quality. The tool will give policy makers more confidence that the decisions they make will reduce emissions and have a positive impact on the health and quality of life of the UK population.’ Rachel Yardley, Air Quality & Environment, Ricardo



The Department for Environment, Food and Rural Affairs (Defra) is responsible for meeting the UK’s challenging targets for reducing pollutant emissions under the National Emission Ceilings Directive. It also has ambitious plans to tackle a wide range of air pollution sources set out in the UK’s Clean Air Strategy. Ricardo is working with Defra to develop a scenario modelling tool (SMT) that enables policy makers to investigate the impact of different emissions reduction policy interventions on key air pollutants (ammonia, oxides of nitrogen, particulate matter (PM2.5/PM10), sulfur dioxide and volatile organic compounds) and three of the main greenhouse gases (carbon dioxide, methane and nitrous oxide).

The SMT focuses on the key themes of the UK’s Clean Air Strategy, including emissions from transport, waste, households, energy, industry and agriculture. The tool enables Defra’s policy makers to quickly model the effects of one measure or several different measures on emissions from each sector with projections through to 2050. The SMT is fully customisable, enabling policy makers to explore the impact of different underpinning assumptions such as technology uptake rates and temporal emissions profiles. It is a powerful tool for informing policy development at national and local scales, supporting delivery of objectives set out in the Clean Air Strategy and the National Air Pollution Control Plan.

Ricardo has a proven track record in delivering high profile, large and complex projects for UK Government. Ricardo’s team includes data scientists, software developers and air quality experts who have in-depth experience of emission inventory development and air quality modelling in the UK, Europe and beyond. Our team includes highly regarded members of COMEAP1, AQEG2 and TFEIP3.


Ongoing user consultation and refinement: Developing the SMT has involved extensive consultation, rigorous testing and effective collaboration of a large project team with diverse expertise. This was achieved through a programme of workshops and progress monitoring, and was overseen by a user steering group.

The Ricardo team is working closely with Defra and other stakeholders to ensure the final version of the SMT meets the needs of future users – a tool that is easy to use, fast to run and delivers data outputs in a format that can be readily used and understood by policy makers, scientists and modellers.

Standalone digital solution: The SMT uses powerful, cloud-based, open-source technologies that are cost-effective and enable Defra to take full ownership of the SMT at the end of the contract. With all calculations and data processing performed server-side, this eliminates any issues relating to compatibility with an end-user’s machine and simplifies ongoing support requirements.

Tailored functionality

  • User-selectable pollutants and regions. The geographic options are based on defined administrative areas such as local authorities, devolved administrations or full UK coverage.
  • The tool includes a user dashboard setting out source apportioned emissions for the selected regions from the baseline National Atmospheric Emissions Inventory (NAEI) projections scenario. This includes interactive visualisations of emissions over time in a graphical format and the spatial distribution of emissions overlaying a map of the selected geography.
  • Users select from a range of pre-defined measures. These have been defined by sector experts to represent the current policy landscape and take into consideration technologically available measures, mutual exclusivity of measures and any cross-cutting impact. The model accounts for interactions between measures applied in the same sector and for cross sector impacts (e.g. electrification reducing vehicle emissions, but potentially increasing power station emissions).
  • Users have flexibility to alter many of the variables in the pre-defined measures and create custom measures from scratch, including the addition of new sources.
  • The SMT includes a cost-benefit analysis of measures and generates marginal abatement cost curves so that policy makers can easily see the costs associated with each package of measures.

Quality assurance: Ricardo’s QA approach combines scientific expertise with digital development and testing to create a robust, reliable tool capable of withstanding the highest levels of scrutiny. All Ricardo processes comply with ISO 9001 (quality management systems) and ISO 27001 (information security) standards.


The SMT enables Defra to:

  • Investigate the impact of different emission reduction policies and measures on key air pollutant emissions.
  • Rapidly model the effects of one or several different measures on emissions from a range of sectors through to 2050.
  • Explore an unlimited number of custom scenarios to test assumptions regarding uptake rates, temporal profiles and numerous other variables.
  • Generate robust evidence that can be used to inform policy development at national and local scales.

With flexibility to update the underlying baseline dataset and create new and detailed scenarios, the SMT can be used by policy makers for many years to come.

1 Committee on the Medical Effects of Air Pollution
2 Air Quality Expert Group
3 Task Force on Emission Inventories and Projections



Start and end dates

06/2019 - 12/2021



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