This page contains some background information behind the statistics. This includes sector classifications, approaches to reporting (source and end-user), how greenhouse gas emissions are measured, uncertainties associated with emissions estimates and inventory improvement programme.
The UK Greenhouse Gas Inventory (UK GHG Inventory) is prepared based on the same data sets as those used in the National Atmospheric Emissions Inventory (NAEI) which incorporates all air pollutants including greenhouse gases. The GHG Inventory is therefore consistent with the NAEI where they overlap.
The UK GHG Inventory is submitted each year on 15th April to the United Nations Framework Convention on Climate Change (UNFCCC) and the European Union (EU). It primarily contains information on greenhouse gas emissions from fossil fuel consumption, industrial production and agriculture. This covers emissions in the UK, Crown Dependencies (Jersey, Guernsey and the Isle of Man) and Overseas Territories (Bermuda, Cayman Islands, Falkland Islands, Gibraltar and Montserrat) that are signatory to the UK agreement of the Kyoto Protocol.
Differences between geographical coverages of reported GHG emissions are summarised in this report:
Source and end-user emissions
There are two methodologies that are used for reporting emissions.
- Emissions by source: When emissions are reported by source, emissions are attributed to the sector that emits them directly.
- Emissions by end-user: When emissions are reported by end-user, this reallocates the emissions by source in accordance with where the end-use activity occurred. This reallocation of emissions is based on a modelling process.
For example, all the carbon dioxide produced by a power station is allocated to the power station when reporting on a source basis. However when applying the end-user method, these emissions are reallocated to the users of this electricity, such as domestic homes or large industrial users.
Each year DECC publishes National Statistics release for emissions by source and by end user.
National Communication and IPCC sectors
For the purposes of reporting, greenhouse gas emissions are allocated into National Communication sectors. These are a small number of broad, high-level sectors, and are as follows: energy supply, business, transport, public, residential, agriculture, industrial processes, land use land use change and forestry (LULUCF), and waste management.
These high-level sectors are made up of a number of more detailed sectors, which follow the definitions set out by the International Panel on Climate Change (IPCC), and which are used in international reporting tables which are submitted to the UNFCCC every year.
A complete mapping of IPCC sectors to National Communication sectors is available below:
Emissions from the Land Use Land Use Change and Forestry (LULUCF) category shown are reported as a net figure, that is emissions from sources minus removals from sinks, following IPCC ‘Good practice guidance for land use, land-use change and forestry’. Carbon sinks are defined by the UNFCCC as “any process, activity or mechanism which removes a greenhouse gas, an aerosol or precursor of a greenhouse gas from the atmosphere".
How are greenhouse gas emissions measured
This is primarily done by converting (numerical) activity data (such as litres of fuel used) into carbon dioxide equivalent data by applying emissions factors.
Fossil fuel combustion is the major source of UK carbon dioxide emissions and so fuel consumption statistics, combined with appropriate emission factors for each source and type of fuel, are used to estimate the majority of greenhouse gas emissions. Emission factors in this case reflect the carbon contents of fuels.
For estimates of emissions by end-users, a simple pro rata method is used to re-allocate estimated emissions from power stations and other fuel processing industries to final users of energy. Emissions by end users are therefore subject to more uncertainty than those by source and should only be used to give a broad indication by sector.
Companies may wish to measure their own greenhouse gas emissions. If so please read below the guidance on measuring and reporting greenhouse gas emissions, as well as how to set targets:
Uncertainties associated with greenhouse gas emissions
There are uncertainties associated with estimating greenhouse gas emissions and removals, as with all datasets, and it is important to understand these uncertainties. Details of the methods involved in calculating uncertainties in emissions estimates are provided in this report:
Improvement programme
The UK is committed to continuous improvement of its GHG emissions estimates in order to improve our understanding, and the quality of our historic emissions, to reduce the uncertainties in the estimates, and to improve our ability to assess progress towards our international and national emissions targets. DECC manages the UK GHG Inventory improvement programme, which determines priorities for inventory development, and this is governed by the cross-Departmental National Inventory Steering Committee (NISC). Outputs of research commissioned or supported under the improvement programme are published on our Publications page.
Quality Assurance processes
The UK implements a sophisticated and thorough system for ensuring the highest quality emissions estimates are produced for international and national reporting purposes, and following relevant international guidance. Details of the Quality Assurance processes which are in place for compiling the UK Greenhouse Gas Inventory are available below:
further information
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