UK Spatial Emissions Methodology

This report describes the methods used to map emissions in the UK National Atmospheric Emissions Inventory (NAEI). The maps provide spatially resolved modelled estimates of emissions compiled at 1x1km resolution for each SNAP2 sector. One set of maps is produced for the most recent inventory year, as the inventory is reported two years in arrears, so maps for 2019 have been produced this year. The mapped emissions data are made freely available on the NAEI website at: https://naei.beis.gov.uk/data/mapping.

The geographical distribution of emissions across the UK is built up from several data sources and methods that are individually tailored to each sector. For large industrial and commercial sources, emissions are compiled based on data from a variety of official UK regulatory sources. For diffuse emission sources, distribution maps are generated using appropriate surrogate statistics that indirectly indicate the spatial distribution of emissions for each sector. The method used for each source sector varies according to the data available.

Emissions maps are a crucial evidence base supporting a variety of Government policy support work at the national level. In particular, the maps are used as input into a programme of air pollution modelling studies. They also provide a spatial overview of emissions and are used to compile, and report gridded emissions to the United Nations Economic Commission for Europe (UNECE) Convention on LongRange Transboundary Air Pollution (CLRTAP). Local area statistics are compiled from the maps and related data as well. For example, carbon dioxide emissions from fuel use at the Local Authority level have been produced for Defra and BEIS since 2005 using data from the NAEI’s mapping work. As of March 2008, these datasets were designated as National Statistics. In addition, the emission maps provide an illustrative and intuitive way for engaging with non-technical audiences who may wish to find out about emissions in their area.

Uncertainty analyses have been undertaken to consider the accuracy of the emission maps for some of the major air quality pollutants and greenhouse gases. Quality ratings have been used for this purpose. The pollutants with the highest quality ratings have a large proportion of their emissions from point sources, whereas pollutants with a greater proportion of their emissions from area sources have lower quality ratings. The distribution of emissions presented in the NAEI maps has been verified for key pollutants which are used in UK scale air quality modelling.