This page contains some background information behind the statistics. This includes greenhouse gases, approaches to reporting (source and end-user), sector classifications and how greenhouse gas emissions are measured.
UK Greenhouse Gas Inventory
UK emissions estimates are derived from the UK Greenhouse Gas Inventory.
The inventory is prepared on behalf of DECC by AEA, which manages the UK's National Atmospheric Emissions Inventory (NAEI) incorporating all air pollutants including greenhouse gases.
The UK submits reports of its emissions data 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:
It is important to review the UK Greenhouse Gas Inventory every year. In doing so the whole historical data series is revised to incorporate methodological improvements, as well as new and revised data.
The revisions policy for DECC’s UK emissions statistics is set out in this document:
The UK Greenhouse Gas Inventory National Statistics User Guide provides a simple guide to the origins and use of data in the compilation of the UK Greenhouse Gas Inventory, which underpins both the National Statistics publication and the UK's other international and national reporting requirements for greenhouse gases. The latest available year of reporting for the inventory is currently 2009. These emissions estimates are published in the 2009 Final UK Figures Statistical Release.
The guide explains where to find the official data on UK greenhouse gas emissions; however, it is not intended to cover all technical and reporting aspects in full detail.
Factsheets for each National Communication sector reported on within the UK’s 1990-2009 Greenhouse Gas Inventory provide a snapshot of historic emissions, sources of emissions and datasets, methodology, uncertainties, improvements and projections:
More information on uncertainties associated with greenhouse gas emissions and removals based on National Communication sectors and the details of the work needed to generate these data is provided in this report:
Details of the Quality Assurance processes which are in place for compiling the UK Greenhouse Gas Inventory:
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.
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. This method, for example, does not take into account higher emissions from increased coal and oil-fired generation used to meet peak domestic demand for electricity. 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:
Gases
Carbon dioxide (CO2) is the most widely known of the Greenhouse gases contributing to global warming. It accounts for 85% of all greenhouse gas emissions in the UK. The other gases included in this ‘greenhouse gas basket’, as defined by the Kyoto Protocol are methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride.
In reporting greenhouse gas emissions, the emission units are presented as ‘carbon dioxide equivalent’. This is in line with international reporting and carbon trading protocols. This is the equivalent amount (or weight) of carbon dioxide that would be emitted into the atmosphere to produce the same estimated radiative forcing (the extent to which a given concentration of a greenhouse gas raises global average temperature) of another gas. This warming influence of gases is known as global warming potential (GWP).
A list of greenhouse gases with its corresponding GWP is available below:
The Kyoto greenhouse gas basket
The six greenhouse gases of the Kyoto basket are:
Carbon dioxide
Carbon dioxide is the main man-made contributor to global warming. Carbon dioxide accounted for about 85 per cent of the UK’s greenhouse gas emissions in 2008.
Carbon dioxide is a colorless, odorless gas which is a natural constituent of air. It is formed by natural processes and by the combustion of fuels containing carbon.
Methane
Weighted by global warming potential, methane (CH4) accounted for about 8 percent of the UK's greenhouse gas emissions in 2007. The major sources for methane are agriculture, waste disposal, leakage from the gas distribution system and coal mining.
Methane is a light, colorless and odorless gaseous hydrocarbon. It is formed during the decomposition of organic matter. It is the main constituent of most natural gas.
Nitrous oxide
Weighted by global warming potential, nitrous oxide (N2O) emissions accounted for about 5 percent of the UK's man-made greenhouse gas emissions in 2007. It is a relatively inert oxide of nitrogen emitted by soils and during the manufacture of nylon.
Hydrofluorocarbons (HFCs)
These have very high global warming potential. However, as they do not contain chlorine, they are not involved in ozone depletion. In 2007, weighted by global warming potential, HFCs accounted for 1.5% of all of UK’s greenhouse gas emissions.
These compounds consist of hydrogen, fluorine, and carbon atoms. These are destroyed naturally in the lower atmosphere. They have many of the useful properties of the CFCs.
Perfluorocarbons (PFCs)
PFCs include compounds such as tetrafluoromethane (CF4) and hexafluoroethane (C2F6). These have a very high global warming potential and an exceptionally long atmospheric lifetime. In 2007, PFCs accounted for only 0.03% of the UK’s greenhouse gas emissions.
Sulphur hexafluoride (SF6)
Sulphur hexafluoride is the most very potent greenhouse gas. It has a global warming potential, roughly 23,900 times greater than that of carbon dioxide. Nonetheless, its capacity to effect global warming is restricted since the gas flows to the bottom of the atmosphere. Weighted by global warming potential, the contribution of SF6 towards the UK’s greenhouse gas emissions was a little more than 0.1%.
Contacts and further information
Please email the Climate Change Statistics Inbox if you have any questions or comments about the information on this page.
The copyright of information presented or attached in this document may not rest solely with DECC. To find out more, please see our Terms & conditions page.