We've brought together a glossary of terms related to energy and climate change. If you have any suggestions for additional terms, please enter your comments in the form at the bottom of the page.  

A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z


Aerosols A collection of airborne particles, typically less than 100th of a millimetre in size, that reside in the atmosphere.
Aerosol Optical Depth (AOD) A measure of how much light airborne particles prevent from passing through a column of atmosphere. Aerosols tend to absorb or reflect incoming sunlight, thus reducing visibility and increasing optical depth.
Abatement Refers to reducing the degree or intensity of greenhouse gas emissions.
Adaptation Adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities.
Adaptation Fund The Adaptation Fund is a financial instrument under the UNFCCC and its Kyoto Protocol (KP). It was established to finance concrete adaptation projects and programmes in developing countries that are parties to the Kyoto Protocol. The fund is to be financed with a share of proceeds from Clean Development Mechanism (CDM) project activities and other sources of funding. 
Afforestation Planting of new forests on lands that historically have not contained forests.
Alliance of Small Island States (AOSIS) A coalition of small island and low-lying coastal countries that share similar development challenges and concerns about the environment, especially their vulnerability to the adverse effects of global climate change. It functions primarily as an ad hoc lobby and negotiating voice for small island developing states (SIDS) within the United Nations system.
Anthropogenic greenhouse emissions Greenhouse gas emissions resulting from human activities.
Assigned amount unit (AAU) A tradable Kyoto Protocol unit equal to one metric tonne of CO2 equivalent. Each Annex I party issues AAUs up to the level of its assigned amount. Assigned amount units may be exchanged through emissions trading.
Attribution The process of assigning causes to detected climate change, whether man-made or natural.   


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Berlin Mandate Adopted at COP-1, the mandate that launched negotiations leading to the adoption of the Kyoto Protocol.
Biomass fuels or biofuels A fuel produced from dry organic matter or combustible oils produced by plants. These fuels are considered renewable as long as the vegetation producing them is maintained or replanted, such as firewood, alcohol fermented from sugar, and combustible oils extracted from soy beans. Their use in place of fossil fuels cuts greenhouse gas emissions because the plants that are the fuel sources capture carbon dioxide from the atmosphere.
Biosphere The part of the Earth consisting of living organisms, including in the atmosphere, on land and in the ocean.
Bunker fuels Fuels consumed for international marine and air transport. 


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CACAM  Negotiating coalition of countries of central Asia and the Caucasus, Albania, and the Republic of Moldova.  
Capacity building  In the context of climate change, the process of developing the technical skills and institutional capability in developing countries and economies in transition, to enable them to address effectively the causes and results of climate change.  
Carbon market A term used to designate greenhouse gas emissions trading systems, be these cap-and-trade systems – imposing a cap on aggregate emissions levels but allowing trade in allowances between states or covered entities – or baseline-and-credit systems, which define an emissions baseline and reward verified emission reductions beyond that baseline with tradable offset credits. The term comes from the fact  carbon dioxide is the predominant greenhouse gas and other gases are measured in units called 'carbon-dioxide equivalents'.
Carbon sequestration The process of removing carbon from the atmosphere and depositing it in a reservoir. The term may also be used to refer to the process of carbon capture and storage, where carbon dioxide (CO2) is removed from flue gases, such as on power stations, before being stored in underground reservoirs.
CBD Convention on Biological Diversity.
Certified emission reductions (CER)

Instruments issued under the United Nations Clean Development Mechanism for approved and verified emission reduction and sequestration projects undertaken in developing countries for greenhouse gases. The Kyoto Protocol allows national and corporate reduction goals for greenhouse gases to be met through the use of CERs.

CFC Chlorofluorocarbon – a class of chemical compounds that deplete ozone.
CH4 Methane
Clean Development Mechanism (CDM)

One of the ‘flexible mechanisms’ under the Kyoto Protocol. It allows companies to undertake projects, in countries without a Kyoto target, designed to reduce greenhouse gas emissions and contribute to sustainable development. Such projects are then credited with ‘Certified Emissions Reductions’ (CERs), which governments can use to meet their Kyoto targets and companies can use to meet their allocations under the EU Emissions Trading Scheme (EU ETS).

Clearing house  A service that facilitates and simplifies transactions among multiple parties.
Climate Average weather and its variability over a period of time, ranging from months to millions of years. The World Meteorological Organization standard is a 30-year average.
Climate change A change in the climate's mean and variability for an extended period of decades, or more.
Climate feedback   When an initial process in the climate leads to a change in another process in the climate, which in turn influences the initial one. A positive feedback intensifies the original process while a negative feedback reduces it. A warming climate could increase the release of CO2 from soils. Since CO2is a greenhouse gas, the additional release of it  would further warm the climate – this would be an example of a positive feedback.  
Climate models   A mathematical representation of the climate system, based on its physical, chemical and biological components, in the form of a computer programme.
CMS Convention on Migratory Species, also known as the the 'Bonn Convention'.  
CO2 Carbon dioxide
Common Reporting Format (CRF)  A series of standardised data tables containing mainly numerical information, submitted electronically by Annex I parties.
Compliance Fulfilment by countries/businesses/individuals of emission and reporting commitments under the UNFCCC and Kyoto Protocol.
CSD United Nations Commission on Sustainable Development


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Deforestation Conversion of forest to non-forest. Examples of deforestation include conversion of forestland to farms, ranches, or for urban use.
Designated National Authority (DNA)  An office, ministry, or other official entity appointed by a party to the Kyoto Protocol to review and give national approval to projects proposed under the Clean Development Mechanism. The main task of the DNA is to assess potential CDM projects to determine whether they will assist the host country in achieving its sustainable development goals, and  provide a letter of approval to project participants in CDM projects.


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Emission reduction unit (ERU) A unit equal to one metric tonne of CO2 equivalent, converted from either an assigned amount unit (AAU) or removal unit (RMU) and issued to project participants in Joint Implementation project activities.
Emissions trading 

One of the three Kyoto mechanisms, by which an Annex I party may transfer Kyoto Protocol units to – or acquire units from – another Annex I party.  An Annex I party must meet specific eligibility requirements to participate in emissions trading. As set out in Article 17 of the Kyoto Protocol, emissions trading allows countries that have emission units to spare, i.e. emissions permitted to them but not 'used', to sell this excess capacity to countries that are over their targets.

El Niño Southern Oscillation (ENSO) El Niño is a periodic warming of the tropical eastern Pacific Ocean associated with a fluctuation in the low latitude pressure system known as the Southern Oscillation. This atmosphere-ocean interaction is known as ENSO, and normally occurs on timescales of between two to seven years.
ESCAP United Nations Economic and Social Commission for Asia and the Pacific
European Union (EU) As a regional economic integration organisation, the EU is a party to both the convention and the Kyoto Protocol. However, it does not have a separate vote from its member states. Because the EU signed the convention when it was known as the EEC (European Economic Community), the EU retains this name for all formal convention-related purposes. Members are Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, and the United Kingdom.


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FAO Food and Agriculture Organization of the United Nations
Fossil fuels Non-renewable sources of energy formed from biomass placed in the Earth millions of years ago, which when burned produce carbon dioxide. Examples include coal, oil, and natural gas.
Fugitive fuel emissions Greenhouse gas emissions as by-products, waste or loss, in the process of fuel production, storage, or transport. Examples include methane given off during oil and gas drilling and refining, or leakage of natural gas from pipelines.


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GATT General Agreement on Tariffs and Trade
GCOS Global Climate Observing System
Geosphere The non-living, solid portion of the Earth, including rocks.
Global dimming   The reduction in the amount of solar radiation at the Earth's surface through the presence of aerosols.

Global Environment Facility (GEF) 

An independent financial organisation that provides grants to developing countries for projects that benefit the global environment and promote sustainable livelihoods in local communities. The parties to the convention assigned operation of the financial mechanism to the Global Environment Facility (GEF) on an on-going basis, subject to review every four years. The financial mechanism is accountable to the COP.

The GEF also serves as financial mechanism for the following conventions:

  • Convention on Biological Diversity (CBD) 
  • United Nations Framework Convention on Climate Change (UNFCCC) 
  • Stockholm Convention on Persistent Organic Pollutants (POPs) 
  • UN Convention to Combat Desertification (UNCCD)

Although not linked formally to the Montreal Protocol on Substances that Deplete the Ozone Layer (MP), the GEF supports implementation of the protocol in countries with economies in transition.

Global warming A rise in the Earth's temperature. It is often used with respect to the observed increase since the early 20th century.
Global warming potential (GWP)  An index representing the combined effect of the differing times greenhouse gases remain in the atmosphere and their relative effectiveness in absorbing outgoing infra-red radiation. It is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming – a relative scale that compares the gas in question to that of the same mass of CO2 (whose GWP is by convention equal to one). A GWP is calculated over a specific time interval and this time interval must be stated whenever a GWP is quoted or else the value is meaningless.
GOOS  Global Ocean Observing System
Greenhouse gases (GHGs)  The atmospheric gases responsible for causing global warming and climate change. The major GHGs are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N20). Less prevalent, but very powerful greenhouse gases are hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). They absorb thermal infra-red radiation emitted by the Earth's surface, the atmosphere and clouds.
GTOS Global Terrestrial Observing System
Gulf Stream / North Atlantic Drift The Gulf Stream is a warm ocean current originating near the Caribbean and the Gulf of Mexico, which follows the east coast of the USA before turning into the North Atlantic Drift towards north-west Europe. This combined system transports heat from low to high latitudes, keeping north-west European winter temperatures higher than they would otherwise be.
GWP Global warming potential


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HFC Hydrofluorocarbons


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ICAO International Civil Aviation Organization
ICCP International Climate Change Partnership
ICLEI International Council of Local Environmental Initiatives
IEA International Energy Agency
IGO Intergovernmental organisation.
IMO International Maritime Organization
Implementation Actions (legislation or regulations, judicial decrees, or other actions) that governments take to translate international accords into domestic law and policy.
Intergovernmental Panel on Climate Change (IPCC)  Set up in 1988 to provide governments with the most up-to-date assessments of the scientific, technical and socio-economic aspects of climate change. The IPCC's assessments provide the most authoritative and comprehensive view of climate change, and inform the development of domestic climate policy and the UK position in international climate negotiations. For example, the Fourth Assessment Report provided the rationale for the Bali Action Plan and scientific knowledge to UN climate negotiations in Copenhagen in December 2009.
International Climate Change Partnership Global coalition of companies and trade associations committed to constructive participation in international policy making on climate change. 
IOC Intergovernmental Oceanographic Commission
ISO International Standards Organization


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Joint Liaison Group (JLG) Group of representatives of UNFCCC, CBD, and UNCCD secretariats set up to explore common activities to confront problems related to climate change, biodiversity and desertification.
Joint implementation (JI) Allows companies to undertake projects in countries with a Kyoto target, to reduce greenhouse gas emissions. Such projects are then credited with ‘Emissions Reduction Units’ (ERUs), which governments can use to meet their Kyoto targets and companies can use to meet their allocations under the EU Emissions Trading Scheme. There are two different procedures for JI, depending on the host country’s eligibility requirements. These are commonly referred to as ‘Track 1’ and ‘Track 2’. Track 1 is subject to supervision by the host country. Track 2 is subject to international supervision by the Supervisory Committee for JI.
JUSSCANNZ  Represents non-EU industrialised countries that occasionally meet to discuss various issues related to climate change. The members are Japan, the United States, Switzerland, Canada, Australia, Norway and New Zealand. Iceland, Mexico, and the Republic of Korea may also attend JUSSCANZ meetings.
JWG Joint working group


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Kyoto Protocol  An international agreement setting targets for industrialised countries to cut their greenhouse gas emissions. These gases are considered at least partly responsible for global warming. The protocol was agreed in 1997, based on principles set out in a framework convention signed in 1992.
Kyoto mechanisms Three procedures established under the Kyoto Protocol to increase the flexibility and reduce the costs of making greenhouse gas emissions cuts; they are the Clean Development Mechanism, Emissions Trading and Joint Implementation.  

The Kyoto Protocol allows emissions-reduction projects to be carried out in various countries, resulting in credits for the corresponding reductions or limitations. The Kyoto Mechanisms are based on the fact emissions of greenhouse gases contribute equally to global warming wherever they come from, so companies can choose to reduce emissions where it is cheapest for them to do so. In countries without a Kyoto target (in other words, developing countries), projects operate under the Clean Development Mechanism. In countries with a target, projects operate under a process known as Joint Implementation (JI).


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Land use, land-use change, and forestry (LULUCF) A greenhouse gas inventory sector that covers emissions and removals of greenhouse gases resulting from direct human-induced land use, land-use change and forestry activities.  
La Niña

The cold phase of ENSO leading to extensive cooling of the central and eastern Pacific.

Leakage  The portion of cuts in greenhouse gas emissions by developed countries – countries trying to meet mandatory limits under the Kyoto Protocol – that may reappear in other countries not bound by such limits. For example, multinational corporations may shift factories from developed countries to developing countries to escape restrictions on emissions.
Least Developed countries (LDCs)  The World’s poorest countries. The criteria currently used by the Economic and Social Council (ECOSOC) for designation as an LDC include low income, human resource weakness and economic vulnerability. Currently 50 countries have been designated by the UN General Assembly as LDCs.
Least Developed Countries Expert Group (LEG)   A group established as part of the Marrakesh Accords to provide advice to LDCs on the preparation and implementation of national adaptation programmes of action. It is composed of 12 experts, including five from African LDC parties, two from Asian LDC parties, two from small island LDC parties, and three from Annex II parties. To ensure linkages between the LDC expert group and the CGE on adaptation issues, at least one member of the LDC expert group from an LDC and one from an Annex II party are also members of the CGE. The LDC expert group meets twice a year.
Least Developed Country Fund (LDCF)  Established to support a work programme to assist LDCs carry out, inter alia, the preparation and implementation of national adaptation programmes of action (NAPAs). The Global Environment Facility (GEF), as the entity that operates the financial mechanism, has been entrusted to operate this fund.


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Marrakesh Accords Agreements reached at COP-7 that set various rules for operating the more complex provisions of the Kyoto Protocol. The accords include details for establishing a greenhouse gas emissions trading system, implementing and monitoring the protocol's CDM, and setting up and operating three funds to support efforts to adapt to climate change.  

In the context of climate change, a human intervention to reduce the sources or enhance the sinks of greenhouse gases. Examples include using fossil fuels more efficiently for industrial processes or electricity generation, switching to solar energy or wind power, improving the insulation of buildings, and expanding forests and other 'sinks' to remove greater amounts of carbon dioxide from the atmosphere.

Montreal Protocol

The Montreal Protocol on Substances that Deplete the Ozone Layer was adopted in Montreal in 1987, and subsequently adjusted and amended in London (1990), Copenhagen (1992), Vienna (1995), Montreal (1997) and Beijing (1999). It controls the consumption and production of chlorine- and bromine-containing chemicals that destroy stratospheric ozone, such as chlorofluorocarbons, methyl chloroform, carbon tetrachloride, and many others.


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N20 Nitrous oxide
No-regrets options

Technology for reducing greenhouse gas emissions of which other benefits (in terms of efficiency or reduced energy costs) are so extensive that the investment is worth it for those reasons alone. For example, combined-cycle gas turbines – in which the heat from the burning fuel drives steam turbines while the thermal expansion of the exhaust gases drives gas turbines – may boost the efficiency of electricity-generating plants by 70%.


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OECD Organisation for Economic Co-operation and Development
OPEC Organization of Petroleum Exporting Countries
Ozone A molecule, which in the upper atmosphere (stratosphere) filters potentially damaging ultraviolet light from reaching the Earth's surface.


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Climate prior to the development of climate-measuring instruments, details of which are acquired from so-called proxy data, e.g. ice sheets, tree rings, sediment and rocks.   

PFC Perfluorocarbon

An international agreement linked to an existing convention, but as a separate and additional agreement that must be signed and ratified by the parties to the convention concerned. Protocols typically strengthen a convention by adding new, more detailed commitments.  


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Quantified Emissions Limitation and Reduction Commitments (QELROs)

These are the legally binding targets and timetables under the Kyoto Protocol for the limitation or reduction of greenhouse gas emissions by developed countries as inscribed in Annex B of the Kyoto Protocol. They represent the overall emissions target for each country for the first commitment period, expressed as a percentage of the base year (1990). Most countries are required to achieve a target of less than 100% of 1990 emissions, with the exception of Australia, Iceland, New Zealand, Norway, the Russian Federation and the Ukraine.


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Formal approval, often by a Parliament or other national legislature, of a convention, protocol, or treaty, which enables a country to become a party. Ratification is a separate process that occurs after a country has signed an agreement. The instrument of ratification must be deposited with a 'depositary' (in the case of the Climate Change Convention, the UN Secretary-General) to start the countdown to becoming a party (in the case of the convention, the countdown is 90 days). 

Recommendation A formal act of the COP that is weaker than a decision or a resolution and is not binding on parties to the Climate Change Convention.
Reforestation  Replanting of forests on lands that have previously contained forests but that have been converted for some other use.
Regional groups

Alliances of countries, in most cases those sharing the same geographic region, that meet privately to discuss issues and nominate bureau members and other officials for activities under the Climate Change Convention. The five regional groups are Africa, Asia, Central and Eastern Europe (CEE), Latin America and the Caribbean (GRULAC) and the Western Europe and Others Group (WEOG).


A component or components of the climate system where a greenhouse gas, or a precursor of a greenhouse gas, is stored. Trees are 'reservoirs' for carbon dioxide.

Rio Conventions

Three environmental conventions, two of which were adopted at the 1992 Earth Summit in Rio de Janeiro. These are the United Nations Framework Convention on Climate Change (UNFCCC) and the Convention on Biodiversity (CBD). The third convention, the United Nations Convention to Combat Desertification (UNCCD), was adopted in1994.

The issues addressed by the three treaties are related – in particular, climate change can have adverse effects on desertification and biodiversity – and through a Joint Liaison Group, the secretariats of the three conventions take steps to coordinate activities to achieve common progress.

Removal unit (RMU)

This is a Kyoto Protocol unit equal to one metric tonne of carbon dioxide equivalent. RMUs are generated in Annex I parties by LULUCF activities that absorb carbon dioxide.


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SF6  Sulphur hexafluoride

Any process, activity or mechanism that removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas, from the atmosphere. Forests and other vegetation are considered sinks because they remove carbon dioxide through photosynthesis.

Spill-over effects
Reverberations in developing countries caused by actions taken by developed countries to cut greenhouse gas emissions. For example, emissions reductions in developed countries could lower demand for oil and thus international oil prices, leading to more use of oil and greater emissions in developing nations, partially off-setting the original cuts. Current estimates are that full-scale implementation of the Kyoto Protocol may cause 5-to-20% of emissions reductions in industrialised countries to 'leak' into developing countries.

Sustainable development

Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.


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Technology transfer A broad set of processes covering the flows of know-how, experience and equipment, for mitigating and adapting to climate change among different stakeholders.
Thermohaline Circulation (THC) The world's large-scale ocean circulation driven by differences in temperature and salinity of the water masses.  


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Umbrella group A loose coalition of non-European Union developed countries formed following the adoption of the Kyoto Protocol. Although there is no formal membership list, the group usually includes Australia, Canada, Iceland, Japan, New Zealand, Norway, the Russian Federation, Ukraine, and the United States.
UN  United Nations 
UNCCD United Nations Convention to Combat Desertification
UNCED United Nations Conference on Environment and Development 
UNCTAD United Nations Conference on Trade and Development 
UNDP United Nations Development Programme 
UNECE United Nations Economic Commission for Europe 
UNEP United Nations Environment Programme 
UNFCCC United Nations Framework Convention on Climate Change
UNIDO United Nations Industrial Development Organization
Uniform report format  A standard format through which parties submit information on activities implemented jointly under the Climate Change Convention.
Urban Heat Islands A metropolitan area that is significantly warmer than its surroundings. 
Urbanisation The loss removal of the rural characteristics of a town or area – a process associated with the development of civilization and technology.


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Voluntary commitments A draft article considered during the negotiation of the Kyoto Protocol that would have permitted developing countries to voluntarily adhere to legally binding emissions targets. The proposed language was dropped in the final phase of the negotiations. The issue remains important for some delegations and may be discussed at upcoming sessions of the Conference of the Parties.
Vulnerability The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate variation to which a system is exposed, its sensitivity, and its adaptive capacity.  


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WCC World Climate Conference 
WEOG Western European and Others Group (United Nations regional group)
WHO World Health Organization 
WMO World Meteorological Organization 
WSSD World Summit on Sustainable Development 
WTO World Trade Organization 


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