A climate change glossary



Additionality: Describes action which actually reduces carbon emissions. Important, especially in the context of carbon offsets, to distinguish from action that makes no difference because the emission reduction would have happened anyway.

Anthropogenic climate impacts: Changes due to human activity rather than nature. For example, factory emissions or deforestation, rather than a smoking volcano.



Biofuel: Fuel from organic matter such as wood, alcohol and vegetable oil. Advocates suggest that if we can produce biofuels sustainably (ie grow them as fast as we burn them), we are not increasing overall levels of CO2 in the atmosphere and they therefore make a great renewable source of energy. Critics say it needs a lot of farmland, it's a bad use of food products, and farming uses a lot of energy and pesticides.

Biomass: Plant material, vegetation, or agricultural waste. Can be used as a fuel or energy source (see biofuel) as an alternative to fossil fuel.

Building regulations: Potentially a way to reduce energy use in buildings (for heating, cooling, lighting) which typically accounts for around 40% of CO2 emissions in developed countries. Tend to be resisted by the building industry because they raise costs.



Cap and trade: An approach to controlling GHG emissions which combines the market with regulation. An overall limit (cap) is set for a specific time period. Individual parties receive permits to produce a set amount of emissions. Those with low emissions may sell unused permits. Others buy them to help meet their quota.

Carbon: One of the building blocks of life, central to all living things and currently essential part of fuel. When the fuel burns, the carbon combines with oxygen to become carbon dioxide or carbon monoxide.

  • Capture and Storage (CCS): The aim is to prevent CO2 entering the atmosphere by capturing and storing it in, for example, old oil and gas fields.
  • Credits: A new currency, with fluctuating value based on supply and demand as in any market. A carbon credit represents an amount of carbon (or CO2) that can be traded.
  • Cycle: The sequence which sees carbon moving between the atmosphere, oceans and land. Human activities such as deforestation and the burning of fossil fuels contribute to the cycle and can disrupt it if left unchecked.
  • Dioxide: The most famous of the greenhouse gases. It occurs naturally at about 0.036% of the Earth's atmosphere and at these levels is essential to life on Earth. But since industrialisation, CO2 levels in the atmosphere have increased dramatically, largely due to burning fossil fuels and forest clearance.
  • Footprint: The amount of carbon emissions associated with an activity or organisation.
  • Intensity: The quantity of CO2 emissions relative to units of energy used, or units of economic output. Reducing intensity can achieve lower emissions while expanding economic activity.
  • Monoxide: CO, rather than CO2. A poisonous gas that occurs when carbon is not fully burned, for example in faulty gas appliances and car exhausts.
  • Neutral: Having no net effect on carbon levels.
  • Offset: Buying and 'retiring' (rather than selling on) an emission reduction that has been achieved or will be achieved by a third party. This compensates for emissions. Companies can buy credits through carbon trading, or investing in a specific project.
  • Positive: Refers to organisations that go beyond carbon neutrality. A carbon positive company would actively drive new carbon markets and develop climate-friendly products or services, effectively achieving negative emissions in a positive way.
  • Sequestration: Processes that remove carbon from the atmosphere, such as growing trees.
  • Sinks: A natural or manmade reservoir (but not for providing drinking water) capable of absorbing more CO2 than it releases. An important part of the carbon cycle; common examples are soil, trees and oceans.
  • Tax: A tax on carbon emissions based on the carbon content of the fuel. Designed to encourage emission reductions.
  • Trading: A market-based approach which allows traders to buy and sell carbon credits. This can help organisations to reach emissions targets in a cap and trade scheme.

CFCs (chlorofluorocarbons): Man-made gases responsible for ozonedepletion, but also greenhouse gases. The 1987 Montreal Protocol has led to CFCs being replaced by HCFCs and HFCs, both of which are also powerful greenhouse gases.

Climate: The average pattern of weather over a period for a particular region, including aspects such as rainfall, temperature and humidity.

  • Change: Changes in temperature, rainfall and other aspects of climate.
  • Models: These are quantitative, computer-based models designed to simulate global climate and weather patterns.

Combined Heat and Power (CHP) or Co-generation: Production of two useful forms of energy from the same process or source, usually heat and electricity. Traditional power stations waste the heat.



Emissions: Gases that are emitted to the atmosphere.

  • Absolute: The weight of emissions, eg in tonnes.
  • Direct: Emissions directly from the facilities, plants and owned transport fleets of a company or organisation. See indirect emissions.
  • Indirect: Emissions associated with the activities of a company or organisation, but released from the facilities, plants or transport fleets of a third party. These may arise from the generation of bought electricity or the use of products by customers.
  • Normalised: Linking emissions to a level of activity, such as company turnover. Not to be confused with absolute emissions.

Energy efficiency: The relationship between the amount used and what you get out of it. Improving efficiency means changing building and process designs or switching technologies, but also behaviour change to stop wasting energy, eg by switching off unused lighting. Efficiency brings economic and environmental benefits.


Forests: One of the major carbon sinks. There are a variety of definitions based on tree height.

  • Afforestation: Planting trees where there haven't been any.
  • Deforestation: Felling trees where there were some, usually so the land can be used for something else (eg farming, houses, roads, industry).
  • Reforestation: Planting trees in deforested areas.

Fossil fuel: Deposits in the earth made up of hydrocarbons (hydrogen and carbon) in the form of coal, oil or natural gas. When burned they produce carbon dioxide.

Fuel cell: A type of battery, starting to be used in some vehicles in a bid to reduce emissions. Fuel cells produce electricity, heat and water by combining hydrogen and oxygen - no harmful emissions if the fuel source is hydrogen.



Global cooling: An average decrease in temperature of the Earth's atmosphere and oceans. Although not happening on a global scale, the IPCC concluded that relative cooling does occur near some industrial areas because of high aerosol concentrations.

Global dimming: A reduction in the amount of sunlight reaching the Earth. The cooling effect of global dimming is thought by some to have obscured the effects of global warming in recent decades. There was roughly a 5% reduction in sunlight from the 1960s to 1990s, but this trend seems to have reversed during the 1990s.

Global warming: An increase in the temperature of the Earth (near the surface, not inside). It can occur naturally, but the term generally refers to the effect of increased greenhouse gases, which the IPCC has concluded are causing warming.

Global Warming Potential: A measure of how much a greenhouse gas contributes to global warming. Some gases are more 'powerful' than others and therefore have a greater potential.

Greenhouse effect: As in a garden greenhouse, the Earth's atmosphere traps some radiation, which causes warming. This is a natural process, but increasing concentrations of greenhouse gases increases this effect, making the world warmer.

Greenhouse gases (GHGs): The gases that make up and add to the 'blanket' which causes the greenhouse effect. Despite the high profile of carbon dioxide (CO2), water vapour is actually the most abundant GHG - but CO2 concentrations are growing fast. Others include methane, nitrous oxide, and the CFC family.

Greenhouse Gas Protocol: An initiative from the World Resources Institute (WRI) and World Business Council for Sustainable Development (WBCSD) designed to support credible reporting and accounting for GHG emissions. [ www.ghgprotocol.org ]



HFCs (hydrofluorocarbons): A man-made greenhouse gas. Used in refrigeration and insulating foam as a substitute for CFCs and HCFCs, because they don't damage the ozone layer.

Hydrogen: The simplest of elements, and potentially part of the solution to climate change. Hydrogen is a potential fuel, with water the only emission when it is burned. But the hydrogen must first be separated (from water), which requires energy. So there would be little benefit if that separation was powered by fossil fuels. Hydrogen farms - which use renewable energy to produce the gas - are being developed.



Icebergs: A large piece of ice floating on open water after breaking away from a glacier or ice shelf. More icebergs might suggest more melting.

Icecaps: A thick layer of ice permanently covering a mass of land.

Icecores: Long tubes of ice extracted from an ice shelf or sheet and analysed to determine past climate patterns. Some tests on the gas trapped within ice cores show that current carbon dioxide levels are higher than they have been for 440,000 years.

Icesheets: Large glaciers covering an area larger than 50,000 km² (so can also be applied to large enough ice caps). Currently only two in the world (Antarctica and Greenland), both of which seem to be reducing in size.

IPCC (Intergovernmental Panel on Climate Change): Established in 1988 by the World Meteorological Organisation and the United Nations Environment Programme. The IPCC gathers a range of experts to prepare reports and assessments on all aspects of climate change. [www.ipcc.ch ]


Kyoto Protocol: An international agreement drawn up in 1997 in Kyoto, Japan. The Protocol builds on the commitments of the 1992 UNFCCC and requires developed countries to meet emission reduction targets by 2012. At July 2006, 161 states had signed and ratified the treaty. Australia and the United States are notable exceptions who have signed but are not intending to ratify. [ www.unfccc.int ]


Methane capture: Methane is a greenhouse gas arising from sources such as landfills, animal waste and coal mines. Capturing it stops it entering the atmosphere. It is then burnt generate heat - which produces carbon dioxide, but with a much lower climate impact than the original methane.



Ozone depletion: Like CO2, ozone is a greenhouse gas, and at low levels it is a part of smog. At ground level it can harm our health, but in the upper atmosphere it protects us from harmful UV radiation. Gases like CFCs break down ozone leading to depletion or holes in the protective ozone layer. Not to be confused with climate change.



Personal carbon allowances: Based on the idea that we could all have a set amount of carbon to use or 'spend' each year. We would be able to trade allowances and limits would be reduced each year.



Renewable energy: Energy from sources that won't run out. These include wind, the sun, tides, hot rocks and biofuels.

Tools Print page E-mail page Reading Room Get Acrobat Reader


Booklet (pdf)