Frequently asked questions 

This section of the NAEI website allows you to find answers to commonly asked questions about the NAEI or related subjects.

Click on a question below to view the related answer. If you do not find an answer to your query, you can also contact the NAEI team who may be able to help with your query.

How are the emission factors calculated?

The methodology used to derive emission factors and emissions can be found in the most recently published Greenhouse Gas and Air Pollutant inventory reports, available to download from the Reports section of the website.

Are there UK emission maps for previous years?

UK emission maps are only available for the latest inventory year. We do not generate a time series of emissions maps for trend analysis.

Although methodology improvements are applied to calculate emission totals for the full time series (1970-current inventory year; outlined in the most recent GHG and AQ inventory reports), the distribution of the emissions in each sector is not necessarily updated every year. Therefore, comparisons of maps produced in different years may show differences which are due to changes in methodology and not necessarily genuine changes in the emission trend.

Where can I find emissions by Local Authority?

In the data section, the Local Authorities webpage provides links to the available Air Quality and GHG pollutant data.

Are individual inventories available for the UK's Devolved Administrations?

Please see the Air Quality and the Greenhouse Gas inventory reports for England, Scotland, Wales and Northern Ireland in Reports section of the NAEI website.

Where can I find GHG emission factors for electricity and gas?

The Defra/DECC Greenhouse Gas Conversion Factors for Company Reporting are available for download.

When will new emissions data be released?

A guideline to the publication dates of some of the NAEI's deliverables are shown below:

  • UK GHG and air pollutant annual emissions data: Late Spring
  • GHG annual report: Summer
  • AQ annual report: Summer
  • NAEI emissions maps: Summer
  • DA inventory: Autumn
Where can I find NAEI road transport emission factors?

The most recently available road transport emission factors – including cold start, brake & tyre wear and road abrasion – are available with a Guidance note, from the Road Transport Emission Factors page.

Where can I find GHG emission factors for different modes of transport?

As well as the road vehicle emission factors on the NAEI website, GHG emission factors for passenger and freight transport are available from the Defra/DECC Greenhouse Gas Conversion Factors for Company Report https://www.gov.uk/measuring-and-reporting-environmental-impacts-guidance-for-businesses

Where can I find UK road transport statistics?

DfT's Statistics pages have a plethora of data on road transport (and other modes of transport) in the UK. Some of these datasets are used in the compilation of the NAEI (see the latest Inventory Report for more details): https://www.gov.uk/government/organisations/department-for-transport/about/statistics