Overview of greenhouse gases
You can select information about greenhouse gases pollutants below. Each description page will allow you to find out more about the pollutant itself, related issues and a timeseries graph.
The GHG inventory covers the seven direct greenhouse gases under the Kyoto Protocol:
- Carbon dioxide (CO2)
- Methane (CH4)
- Nitrous oxide (N2O)
- Hydrofluorocarbons (HFCs)
- Perfluorocarbons (PFCs)
- Sulphur hexafluoride (SF6)
- Nitrogen trifluoride (NF3)
These gases contribute directly to climate change owing to their positive radiative forcing effect. HFCs, PFCs, SF6 and NF3 are collectively known as the 'F-gases'.
In general terms, the largest contributor to global warming is carbon dioxide which makes it the focus of many climate change initiatives. Methane and nitrous oxide contribute to a smaller proportion, typically <10%, and the contribution of f–gases is even smaller (in spite of their high Global Warming Potentials) at <5% of the total.
Also reported are four indirect greenhouse gases:
- Nitrogen oxides (NOx)
- Carbon monoxide (CO)
- Non-methane volatile organic compounds (NMVOC)
- Sulphur dioxide (SO2)
Nitrogen oxides, carbon monoxide and NMVOCs are included in the inventory because they can produce increases in tropospheric ozone concentrations and this increases radiative forcing (warming of the atmosphere). Sulphur dioxide is included because it contributes to aerosol formation which can either warm (through absorption of solar radiation on dark particles) or cool (from forming cloud droplets and reflecting radiation) the atmosphere.
Important sources and trends
The largest source is the combustion of fossil fuels in the energy sector, typically approximately 70-80% of total emissions. Emissions of CO2, CH4 and N2O arise from this sector. Energy sector emissions have declined since the base year of 1990, primarily due to fuel switching to less carbon–intensive energy sources (e.g. coal to gas in the power sector) and reduced energy intensity of the economy (e.g. declining iron and steel and metal production industries).
The agriculture, industrial processes and product use (IPPU) and waste sectors each generally contribute between 5 and 10% to national emissions.
Emissions from the agriculture sector arise for both CH4 and N2O and a very small amount of CO2. Since 1990, emissions from this sector have declined due to a reduction in livestock numbers, changes in the management of manure and restrictions in the use of synthetic fertiliser.
Emissions of all direct greenhouse gases occur from the IPPU sector. Emissions from this sector include non–energy related emissions from the production and use of cement and lime, chemical industry and metal production as well as F–gases from refrigeration, air conditioning and other industrial and product use. Since 1990, this category has seen a large decline in emissions, mostly due to a reduction in bulk chemical production and metal processing industries and due to changes in process and abatement technology being fitted at large sites.
The Land Use, Land Use Change and Forestry (LULUCF) sector contains absorbers (sinks) as well as sources of CO2 emissions. LULUCF has been a net sink since 1991. Emissions from this source occur for CO2, N2O and CH4 from clearing of forests and vegetation, flooding of land and from application of fertilizers and lime.
The majority of emissions from the waste sector are from CH4 from solid waste disposal on land. Overall emissions from the waste sector have decreased since 1990, mostly due to the implementation of methane recovery systems at UK landfill sites, and reductions in the amount of waste disposed of at landfill sites.
More detailed information and the latest figures are available in the latest National Inventory Report in the Reports section.
Countries that have signed and ratified the Kyoto Protocol are legally bound to reduce their greenhouse gas emissions by an agreed amount. A single European Union Kyoto Protocol reduction target for greenhouse gas emissions of -8% compared to base-year levels was negotiated for the first commitment period, and a Burden Sharing Agreement allocated the target between Member States of the European Union. Under this agreement, the UK reduction target was -12.5% on base-year levels. The first commitment period of the Kyoto Protocol was from 2008 to 2012.
The second commitment period of the Kyoto Protocol will run for eight years, from 2013 to 2020 inclusive. For this second commitment period, alongside the EU and its member States, the UK (including Gibraltar) communicated an independent quantified economy-wide emission reduction target of a 20 percent emission reduction by 2020 compared with 1990 levels (base year). The target for the European Union and its Member States is based on the understanding that it will be fulfilled jointly with the European Union and its Member States. The 20 percent emission reduction target by 2020 is unconditional and supported by legislation in place since 2009 (Climate and Energy Package). Once ratified this Kyoto target will cover the UK, and the relevant Crown Dependencies and Overseas Territories that wish to join the UK’s ratification. As ratification is not yet complete the exact details of the UK’s target for the second commitment period are still being finalised.
The UK Climate Change Act, which became part of UK law in November 2008, introduced an ambitious and legally binding target for the UK to reduce GHG emissions to 80% below base year levels by 2050. This will be achieved by way of legally binding five year Carbon Budgets.
Page last modified: 09 June 2016