Bloom's climate change glossary

A full list of climate change related glossary terms used on this site

Click on a letter to find a definition

Glossary key

  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z

Glossary definitions

  1. A

    Acid rain
    Acid rain is simply rain with higher than normal acidity. Its main cause is emissions of nitrogen and sulphur compounds from burning fossil fuels to power transport, power stations, forest fires, fertiliser and industry.
    An aerator is a device that breaks the flow from your shower head (or other water supply) into a finer spray of droplets - so you get just as wet while using less water.
    Air pollution
    Air pollution usually refers to the presence of any chemical or particulate that alters the normal make-up of our atmosphere, causing direct threats to human health (such as breathing difficulties) or longer-term damage through its effects on our planet's ecosystem. Pollutants include smoke and dust, nitrogen oxides, methane, and the fumes from aerosol sprays and other solvents. Industrial processes and transport are major contributors to air pollution, but it can also be caused by natural processes such as forest fires and volcanoes. See also acid rain.
    A mixture of two or more elements, at least one of which is a metal.
    The atmosphere is the name for the mixture of gases surrounding the earth and retained there by the planet's gravitational pull - our air, in other words. The atmosphere comprises the troposphere, the stratosphere, the mesosphere and the thermosphere.

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  2. B

    Organic matter that can break down or decompose rapidly under natural conditions and processes is referred to as biodegradable. Garden and food waste, animal waste, and most paper products, as well as plastics derived from vegetable content, will biodegrade, but not plastic carrier bags and polystyrene cups, for example.
    Biodiesel is fuel generated from vegetable oil that can be used pure or blended with regular diesel (diesel produced by refining crude oil) in conventional, unmodified diesel engines. It is not the same as waste vegetable oil, otherwise known as 'unwashed biodiesel', which requires engine modification.
    Biodiversity (a contraction of the phrase biological diversity) means the variety of life on earth, or within one particular ecosystem, in terms of the number of distinct biological species present. Tropical rainforests, for example, support a huge variety of species, so are highly biodiverse, while polar regions are far less so. Scientists worry that deforestation, such as that associated with planting crops for biofuels, animal feed and human consumption is reducing biodiversity. See also monoculture.
    Biofuel is a general term for fuel, including biodiesel, that is derived from biomass - living or recently dead organic matter. In general it is made from sugar, starch, vegetable oils or animal fats. Examples include bio-ethanol from energy crops such sugar cane, corn, palm oil, and rape seed.
    Biomass is renewable organic matter that can be used as fuel. It is living or recently dead material - wood and other plant matter, or even animal waste. Fuel derived from biomass is known as biofuel. It does not include fossil fuels, which have formed - and stored their carbon - over millions of years. Because the CO2 released when biomass is burned is balanced by the CO2 absorbed during its production - and because new plant matter is re-growing and absorbing more CO2 all the time - it's regarded as carbon neutral.
    Biomass boiler/stove
    A biomass boiler is a central heating system or a stove powered by biomass (usually wood) rather than fossil fuels form of pellets or wood.

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  3. C

    CFCs (chlorofluorocarbons) are compounds that contain chlorine, fluorine and carbon only. Once commonly used as coolants in fridges and in products such as hairspray, they would travel high up into the stratosphere and were a significant contributor to the hole in the ozone layer. At lower altitudes in the atmosphere they are a powerful greenhouse gas, 10,600 times more effective at warming the climate than CO2, but their overall warming effect is low. Their use has been largely phased out over the last 20 years, though some of their replacements have also been implicated in global warming.
    CFL bulbs
    CFLs are compact fluorescent lamps. They operate on the same principle as fluorescent lights but the tube is folded into a more compact design so they are more versatile and can be used in devices designed to take traditional incandescent bulbs. They use about 80% less electricity than traditional bulbs to produce the same light and last considerably longer. Their mercury content means disposal, especially of broken bulbs, requires extra care. Also referred to as low-energy lightbulbs.
    CHP - combined heat and power
    CHP - also referred to as cogeneration - is a system that recovers the heat produced as a byproduct of electricity generation instead of simply venting it via cooling towers. This recovered heat can then be used for domestic or industrial heating close to the plant.
    CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
    CO2 equivalence
    CO2 equivalence (CO2e) is a way of indicating the global warming potential of a particular greenhouse gas by expressing it in comparison to that of carbon dioxide. One unit of a gas with a CO2e rating of 21, for example, would have the warming effect of 21 units of carbon dioxide emissions (taken over 100 years).
    Car clubs
    Not, in this instance, a club for car enthusiasts, but an organisation providing car rental to members at very short notice and usually for short periods, such as an hour or two.
    Car pooling
    Car pooling - or lift sharing - is a way of reducing CO2 emissions from private transport, especially commuter travel, by sharing journeys. It can be arranged informally among friends and colleagues or, increasingly, through dedicated websites. Its aim is to have fewer cars on the road with more people in each.
    Carbon is the fourth most common chemical element in the universe, and carbon compounds - in other words, carbon chemically combined with other elements - are the basis of all known life forms on earth. Pure carbon appears in many apparently diverse forms, from diamond to graphite to charcoal, but it is much more commonly found in substances such as coal, oil, natural gas, wood and peat that we use for fuel. When we burn these substances to provide energy - either directly in our homes as heat, or in power stations to produce electricity - the combustion process produces 'oxides' of carbon, including the gas CO2.
    Carbon capture
    Carbon capture, carbon sequestration, or CCS (carbon capture and storage) are all terms to describe relatively new technologies designed to let major producers of CO2 emissions, such as fossil fuel-burning power stations, prevent the CO2 they create being released into the atmosphere. Instead it is stored by being injected into underground or undersea geological formations. Some CCS technology is already in operation on a limited scale in other countries but its use is not yet widespread.
    Carbon credit
    One carbon credit allows a business operating within an emissions trading scheme to emit one tonne of CO2. A firm that manages to reduce its carbon emissions to the extent that it does not require all its credits can sell the surplus to other firms who need to exceed their own cap. See emissions trading for more details.
    Carbon footprint
    A person's carbon footprint (or that of a particular household, business or entire community) refers to the CO2 for which they are responsible - whether directly, via their home energy use, their transport use, or indirectly via the embodied energy in the products and services they buy and use. You can work out your carbon footprint using calculators such as the Government's Act On CO2 Calculator.
    Carbon neutral
    A business or a process is described as carbon neutral if it doesn't add to the net amount of CO2 in the atmosphere. This can be achieved either by emitting no CO2 to begin with - by using only renewable energy, say - or by 'offsetting' emissions (a controversial issue) which means compensating for emissions by another action which might reduce atmospheric CO2, such as planting trees. In practice, it is impossible for a person to live in an entirely carbon neutral way because even if you cut out energy consumption derived from fossil fuels, most products and services people rely on will have embodied emissions.
    Cavity walls
    A wall comprising two layers of brick or block separated by a cavity (gap). This air space acts as an insulator, but does so more effectively if filled with an insulating material, such as plastic foam or natural materials like wool or recycled newspaper.
    Climate change
    Climate change is the variation in the average global or regional climate as measured by yardsticks such as average temperature and rainfall. This variation is caused by both natural processes and human activity. Weather is what happens over days or even hours, whereas climate is the average weather measured over a longer period. Increasingly when people refer to climate change, however, they specifically mean the phenomenon of global warming.
    A chemical combination of two or more elements, such as carbon and oxygen in carbon dioxide (CO2).
    Condensing boiler
    A condensing boiler captures and uses energy contained in the water vapour given off when gas or oil is burned. In a non-condensing boiler this vapour leaves via a heat-resistant gas tube, or 'flue', and its energy is wasted. A condensing boiler cools the combustion gases sufficiently that the water vapour condenses back into liquid and its heat is recaptured. Approximately 10% of the energy value of the fuel is contained in this water vapour, so a condensing boiler converts far more of the fuel's energy into heat.

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  4. D

    Dangerous climate change
    Dangerous climate change is a term introduced by the 1992 UN Framework Convention on Climate Change - the treaty that led to the Kyoto protocol. In general terms, it refers to climate change of sufficient severity that it will have a major effect on societies, economies and the wider environment. The definition of what that level is varies, but Defra, for example, defines it as a rise in average global surface temperatures of 1-3 C (taking pre-industrial revolution average surface temperatures as the base).
    Deforestation is the conversion, long term, of areas of forested land to non-forested land through human activity. (Where cleared areas are quickly replanted, it is not regarded as deforestation.) Reforestation is the reversal of that process - i.e. planting trees on land that has historically been forested but has recently been used for other purposes. A less commonly seen term, afforestation, refers to the process of establishing forests on land that has never been forested, or not in recent history.
    Ordinary diesel, like regular petrol, is refined from oil but it is a thicker, heavier liquid with a higher 'energy density' - meaning it offers better fuel economy. On the down side, unless you buy an air filter, diesel exhaust is a significant source of particulates and other sources of air pollution. A type of diesel not derived from petroleum is increasingly widely available, commonly referred to as biodiesel.
    Dioxins are chlorine-containing chemical compounds formed and emitted into the atmosphere usually as byproducts of human activity - waste incineration and fuel combustion being common examples. They are also formed by natural processes such as forest fires and volcanoes. Some dioxins have harmful properties and could, in sufficient concentration, be harmful to the environment and human health.
    Draught proofing
    Draught proofing is the process of filling in unwanted gaps in the fabric of a building to reduce the heat loss and discomfort they cause. Common sources of draughts are gaps round window and door frames, places where pipes enter the building, ill-fitted floorboards, letter boxes and even keyholes. Materials used include foams, brushes and thin sections of rubber, plastic or metal.
    Dual fuel
    A dual-fuel vehicle is one designed to run on a combination of traditional fuels (petrol or diesel) and alternative fuels (such as liquid petroleum gas or biodiesel). The term is usually applied to cars with separate tanks for each fuel but is sometimes used to describe those diesel engines that accept a blend of traditional fuel and bio-diesel.

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  5. E

    Eco-friendly, or environmentally friendly, is a term applied to goods, services, processes or people deemed to do minimal harm to the environment. The term is shorthand for 'ecologically friendly', ecology being the study of the relationships between living organisms and their environment.
    An ecosystem is the term applied to the interaction of a community of different living (organic) species - plants, animals and micro-organisms - with non-living (or inorganic) factors, such as atmospheric gases, temperature and light. When the balance of an ecosystem is changed - by the introduction of new elements or dramatic rises in one or more of them - the normal functioning of the ecosystem can be disrupted.
    Efficiency ratings
    All white goods and other household appliances sold in the UK are now required by law to carry a rating indicating their energy efficiency. Goods are graded A to G, with A the most efficient. Information on the EU-wide labelling scheme is available from the government's environment department, Defra.
    Embodied energy
    Embodied energy - sometimes referred to as 'embedded energy' - is the energy used (and therefore the CO2 emissions) in manufacturing, packaging and transporting a product, material or service. So when calculating the CO2 savings from a new energy-efficient product such as a boiler or washing machine, its embodied energy needs to be taken into account. Usually the energy saved in use will quickly compensate for the embodied energy, but in some cases - such as small urban wind turbines - it may be that a product will use more energy in its manufacture than it will save across its lifetime.
    Emissions are the CO2 (and other greenhouse gases) produced by energy use, usually calculated and stated as an annual tally: also referred to as your carbon footprint. Your personal emissions can be direct - such as the gas you personally use to heat your home or the petrol you burn to power your car - or indirect - meaning the energy use that has gone into the products or services you buy. The latter, such as the emissions caused by the manufacture of your new TV, or the packaging your food comes in, are also referred to as embodied emissions.
    Emissions trading
    Emissions trading exists in countries where there is an overall top limit set on the emissions that industry can produce. Each business has a permit allowing it to produce a certain quantity of CO2 emissions; if it needs to exceed that limit, it must buy additional 'credits' from another business which has produced less than its permitted emissions. In theory, this mechanism means emissions reductions are made with the minimal adverse effect on the wider economy because those industries that find it hardest to cut emissions are helped by those where the cheapest reductions can be made.
    Energy efficiency
    Something that is energy efficient achieves the greatest useful output for the least expenditure of energy, or improves the ratio between the two. For example, energy efficient car engines improve the car's fuel economy.
    Energy efficient
    definition to follow
    Energy intensive
    An energy-intensive process uses a great deal of energy - and therefore produces high emissions - relative to its useful output. As an example, beef production, has recently been cited as an especially energy-intensive industry, while tumble dryers are energy-intensive appliances. Products that are manufactured in an energy-intensive way are also said to be 'emissions heavy'.

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  6. F

    Farmer's market
    Farmers' markets are where producers sell fresh, locally grown produce, or food made with local ingredients, direct to the public. As with organic farming, there is no single, fixed definition but producers should be local (within about 25-30 miles of the market) and selling their own produce - i.e. they are the farmer, family member or direct employee. A large fraction of the produce - particularly during the winter - is grown in artificially-heated greenhouses.
    Fertilisers are given to plants to promote growth. They can be naturally occurring compounds (such as peat) or they can be manufactured - either through natural processes (such as composting) or chemical processes. Fertilisers commonly contain nitrogen, and the use of such fertilisers emits the potent greenhouse gas, nitrous oxide (N20). Using animal manure as fertiliser, though organic, releases another potent greenhouse gas, methane into the atmosphere.
    Fibreglass is a cloth woven from very fine threads of glass and commonly used as an insulating material.
    Fluorescent lights
    A fluorescent bulb or tube uses the flow of electricity to excite mercury vapour in an inert gas (argon or neon), which creates invisible ultraviolet light. A coating of phosphor on the inside of the glass then converts this into visible light - a process known as fluorescence. They have higher energy efficiency and longer life than traditional incandescent bulbs. See also CFLs/low-energy lightbulbs.
    Food miles
    A product's 'food miles' indicate how far it has travelled to get from where it (or its ingredients) were grown to where you eat them. Food freight - especially by air and road - is very carbon intensive.
    Fossil fuels
    Fossil fuels are the deposits of crude oil, natural gas and coal formed by the decay, over millions of years, of organic material (plants, trees animals and bacteria). Because the combustion of fossil fuels releases carbon that has been out of the natural carbon cycle for so long (unlike with living or more recently dead organic matter, known as biomass) it affects the balance between stored carbon and carbon present in the atmosphere as CO2, a greenhouse gas.
    Fuel duty
    Fuel duty is the tax the government levies on fuel used for transportation, imposed at the point of sale.
    Fuel economy
    How many miles a vehicle will travel for each litre of fuel used.

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  7. G

    Geothermal energy is energy from the inner core of the earth where molten rock heats the water just below the surface of the earth, or from the sun's energy trapped just below the earth's surface. This energy, hot water or steam can then be distributed to heat buildings. It is the reason we have natural spas. This natural heat has been used to heat buildings and water supplies since Roman times. See also ground source heat pump.
    Gigawatt hours
    Global warming
    Global warming refers to the increase in the earth's surface (or near-surface) temperature in recent decades due to higher levels of greenhouse gases, and the projected worsening of this effect over time.
    Greenhouse effect
    The greenhouse effect keeps the earth's average temperature at around 14C. Without it, the planet would be too cold to support human life. Greenhouse gases in the atmosphere raise the earth's temperature by trapping energy from the sun after it has hit the earth's surface, rather than allowing it to escape back into space.
    Greenhouse gases
    Greenhouse gases raise the earth's temperature through the greenhouse effect. There are six main examples. As well as carbon dioxide, they include: water vapour, methane, nitrous oxide, ozone and CFCs (which include sulphur hexafluoride, HFCs, and PFCs). Of these, carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, HFCs, and PFCs are controlled under the Kyoto Protocol to limit their concentration in the atmosphere. The heat warming capacity of each gas is measured by its 'global warming potential': how much heat it traps depends on its chemical make-up and how long it stays in the atmosphere.
    Grey water
    Grey water is waste water from baths, showers, washing machines, dishwashers and so on - in other words, water that has been used in the home but does not contain bodily waste - which can be reused for lawn and garden irrigation, say, or for flushing toilets.
    Ground source heat pump
    Electrically powered systems that tap the stable, residual heat stored immediately below the surface of the earth to provide heating and hot water for homes and offices. Also known as geothermal heat pumps. See also geothermal energy.

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  8. H

    Hardwoods and softwoods
    Hardwoods come from broad-leaved trees, usually (but not always) deciduous. They are typically (but, again, there are exceptions) denser than softwoods, which come from coniferous trees. Because hardwoods are generally more resilient than softwoods, they are commonly used for making furniture and flooring, and in construction, particularly for exterior work. The use of tropical hardwoods is a contributor to deforestation, linked to climate change and reduced biodiversity.
    Hummer is the brand name of a 4x4/off-road vehicle manufactured by General Motors and styled after the US military's high mobility multipurpose wheeled vehicle (HMMWV, or Humvee). The Hummer is widely criticised for its very poor fuel economy.
    A hybrid car is one that has both a petrol engine and an electric motor and switches between them according to the driving conditions. It is different from a dual-fuel vehicle, which uses two types of liquid fuel.
    Hydrocarbons are compounds made up of hydrogen and carbon only. All fossil fuels - such as coal, oil and gas - are hydrocarbons, until they are burnt when they mix with oxygen, creating (amongst other gases) CO2.
    Hydropower (or hydroelectric power) is the generation of electricity using the power of falling water.

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  9. I

    Incandescent bulbs
    Incandescents are traditional lightbulbs that use a filament (a thin thread of metal, usually tungsten wire) inside a glass bulb that glows white hot as electricity passes through it. The filament is prevented from burning either by creating a vacuum inside the bulb or filling it with inert gas. They are far less energy efficient than fluorescents/CFLs or LEDs because most of their radiation is given off as heat rather than visible light.
    Inert gas
    Inert gases are those, including helium and neon, that are not normally chemically reactive. The inert gases argon and krypton are often used in sealed double glazing units because they don't conduct heat as well as air, so they provide better insulation.
    Intergovernmental Panel on Climate Change (IPCC)
    The IPCC is an international scientific body that publishes papers and reports on climate change, particularly on topics related to the UN Framework Convention on Climate Change, the treaty that led to the Kyoto protocol.

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  10. K

    Kilowatt-hours (kWh)
    A kilowatt-hour is an amount of energy equivalent to a power of one kilowatt (a thousand watts) running for one hour. The unit is commonly used on electricity meters. If you know how many kilowatt-hours of energy your household uses, you can translate this into kilograms of CO2 emitted by multiplying it by 0.527. A megawatt hour (MWh) is an amount of energy equivalent to the power of one megawatt (a million watts) running for one hour. Similarly, a gigawatt hour (GWh) is a billion watts for one hour, and a terawatt hour (TWh) is a trillion. While your domestic gas bill will be set out in kWh, the output for a power station, for example, will obviously be expressed in one of these much larger units.
    The kitemark is a symbol signifying that a product or service has met a standard set by the British Standards Institution (BSI) Product Services division.
    Kyoto protocol
    An international agreement adopted in December 1997 in Kyoto, Japan. The protocol sets binding greenhouse gas emissions targets for developed countries that would reduce their emissions on average 5.2% below 1990 levels.

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  11. L

    An LED is a light-emitting diode. Its light is produced by an electrical current passing through a semiconductive material, so it does not require a filament like an incandescent bulb. They have a long life span, are durable, more energy efficient than CFLs, or incandescent bulbs cool to the touch and, while they have traditionally been used as small indicator lights, multiple LEDs are increasingly being used for household lighting.
    Lagging is another term for insulating, or for the insulating material itself. To lag means to add material to spaces or containers liable to heat loss - typically hot water pipes and tanks, and loft spaces.
    Landfill is disposal of rubbish by burying it under the ground.
    Liquid petroleum gas (LPG)
    Liquid (or 'liquefied') petroleum gas (LPG) is a mixture of butane, propane and other light hydrocarbons produced either as a by-product of oil refining or from natural gas fields, and used as a vehicle fuel with lower CO2emissions than petrol. At standard temperature and pressure, it's a gas but the mixture can be cooled, or subjected to moderate pressure, and is then transformed into a liquid for ease of storage and transportation. LPG is used in dual-fuel vehicles, where it operates alongside a conventional petrol tank. It is also used in heating appliances.
    Listed buildings
    Listed buildings are those included on a government-approved list as having special architectural or historic interest. Special consent for any alterations is required.

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  12. M

    A megatonne is one million tonnes. It is commonly used to describe the large amounts of CO2 emitted by power stations.
    Mercury (chemical symbol Hg) is a metal that is liquid at standard temperature and pressure. It is used in the manufacture of low-energy lightbulbs (CFLs and other fluorescent lights), and extra care must be taken in their disposal, especially when they are broken, because of mercury's toxicity.
    Methane is a hydrocarbon, the main component of natural gas and among the six greenhouse gases to be curbed under the Kyoto protocol. As a greenhouse gas it is estimated to have a warming effect about 25 times as great as CO2. (Compared to CO2 its effects are greater but last for a shorter period). As a fuel, it is used in electricity generation and in the form of compressed natural gas it can be used as vehicle fuel. Methane is produced during the decomposition of many materials in landfill, while about 16% of methane emissions are caused by livestock's digestive processes.
    Microgeneration is small-scale home production of electricity and heat using technology that produces little or no CO2. Common examples include ground source heat pumps, solar panels and wind turbines. Where successful, people can meet their own energy needs and also sell excess energy back to the grid.
    Mineral wool
    Mineral wool refers to any of several lightweight, fibrous materials used as insulation and created by blowing air or steam through molten blast-furnace slag (slag wool), molten rock (rock wool) or molten glass (glass wool). Definitions vary, but fibreglass is sometimes referred to as a mineral wool.
    Monoculture is the practice of planting a single crop, or genetically similar crops, over a wide area. Its advantages to growers are that the crop may thrive in conditions tailored to its success and without competition from other species. However, the practice will also reduce the region's biodiversity by limiting the number of other species for which it is a suitable habitat. Scientists warn that extensive forest clearance to make way for widespread growth of crops such as sugarcane to create biofuels is creating a monoculture harmful to biodiversity. The opposite of a monoculture is a polyculture.

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  13. N

    National Grid
    The grid, or National Grid, is a privately owned network of electricity supply lines that stretch from the power stations where the electricity is generated to the homes and businesses where it is used. In some parts of the UK, local or domestic microgeneration may make it feasible to live "off grid", while some homes in remote parts of the country have no choice because it does not reach them. In some cases, microgeneration means there is potential for people to sell surplus electricity back to the grid.
    Nitrogen oxides
    Nitrogen oxides are compounds of nitrogen and oxygen, two elements that do not normally react with each other but will do so during high temperature combustion – such as in a car engine. Examples include nitric oxide (NO) and nitrogen dioxide (NO2), which contribute to air pollution, and nitrous oxide (N2O), which is a major greenhouse gas. Although its warming effect is far less than CO2, it persists in the atmosphere for far longer, so measured over 100 years its impact is 298 times greater.

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  14. O

    Offsetting, or carbon offsetting, refers to the (highly contentious) principle that a company or individual can mitigate or even entirely neutralise the effects of their CO2 emissions by investing in programmes that promote energy-efficiency or CO2 absorption, such as providing low-energy lightbulbs or planting trees.
    The Office of Gas and Electricity Markets (Ofgem) is the government agency responsible for regulating the energy market in the UK. It describes its purpose as "protecting consumers... by promoting competition... and regulating the monopoly companies which run the gas and electricity networks". Its aims also include curbing climate change by helping energy providers meet environmental goals. There is also a non-governmental equivalent, the consumer watchdog Energywatch.
    Oil refining
    Oil refining is the process of taking crude oil and turning it into fuels such as petrol and diesel. Crude oil varies in its composition, consisting of hydrocarbons and other organic compounds containing nitrogen, oxygen and sulphur. Refining oil requires energy and releases air-polluting chemicals. However, the majority of the CO2 produced by oil is emitted only once it has been turned into fuel and then burnt.
    Organic farming
    There is no universally accepted definition of organic farming, and each country regulates what can and cannot be labelled "organic". In general, it describes a form of agriculture that avoids use of synthetic fertilisers, pesticides, growth regulators, and livestock feed additives, and relies instead, as far as possible, on "natural" products and techniques - such as crop rotation and animal manures.
    Ozone is made up of three oxygen atoms. It has benefits and dangers depending on where in our atmosphere it occurs: near ground level, it is a pollutant that affects respiration; 10-50km up, in the stratosphere, the ozone layer filters out potentially harmful ultraviolet rays (which cause skin cancer) from reaching the earth. Ozone also functions as a greenhouse gas, though it is considered a less potent one than CO2.

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  15. P

    Particulates - sometimes referred to as particulate matter or just particles - are tiny pieces of dust, soot and other materials suspended in the atmosphere. These can be produced naturally, by volcanoes or forest fires for example, but are also caused by incomplete combustion of fossil fuels, particularly from diesel engines. Because diesel is a denser fuel than petrol, it needs more oxygen for all its hydrocarbons to react completely, and the unburnt carbon - soot or black smoke - is emitted through the exhaust pipe.
    Payback, or the payback period, is the time it takes for savings (often, in this context, in energy bills) to overtake the initial capital outlay on installation of an energy-saving device or system.
    A pesticide is a substance used to kill a pest, and in a farming context a pest is anything that attacks or competes with crops. Hence, there are many different types of pesticides: for example, insecticides kill insects, and herbicides kill weeds. The chemicals used in pesticides can sometimes be toxic to humans, however, so organic farming endeavours to use natural rather than synthetic substances as pesticides.
    A car enthusiast; often used to describe those who are most reluctant to limit their car use or petrol consumption.
    Photovoltaic cell
    'Photovoltaics' are materials that produce electricity from sunlight. A single photovoltaic cell can be used to power small devices such as calculators; combined in solar panels they can be used to power solar water heating. Most cells are manufactured from silicon.
    Planning permission
    Planning permission is consent, usually from a local council, to build on land, or change the use of land or buildings. Significant structural change, such as that often associated with microgeneration projects, is likely to require planning permission. Changes to listed buildings require additional, separate consent.
    A polymer is a giant molecule made up of thousands of atoms. It can be natural or man-made (synthetic). Many plastics in everyday use are polymers, such as polythene or PVC; but then so is cellulose, which makes up wood pulp from which paper is manufactured.
    In a central heating system, the programmer is the device containing a clock that turns the heating and hot water systems on and off at designated times, while the thermostat sets the maximum temperature.

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  16. R

    Renewable energy
    Renewable energy comes from natural sources that can be replenished and not permanently depleted - such as biomass, hydro-power, geothermal heat, solar power, wind power, and wave and tidal power - and most of which do not produce CO2emissions. They are unlike fossil fuels, which took millennia to form and cannot be replenished.
    Renewables obligation
    A renewables obligation is the legal requirement for UK energy providers to source a certain percentage (currently 8%) of their energy from renewable sources. They are awarded renewable obligation certificates (ROCs) to demonstrate that they have done so.

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  17. S

    An SUV is a sports utility vehicle, an American term for what in the UK tends to be called a 4x4 or four-wheel drive, although in fact not all SUVs are actually four-wheel drive.
    Secondary glazing
    Secondary glazing is a less effective form of double glazing, used where the latter is unaffordable or undesirable in some way (such as in listed buildings). A separate layer of glass or plastic is fitted to the inside of the existing window frame. The gap between the two panes determines its effectiveness in insulating against heat loss and noise.
    A semiconductor is a solid material that is able to conduct electricity, but with conductivity less than that of a good conductor and greater than an insulator. Semiconductors include silicon, and are used in the manufacture of photovoltaic cells, as well as computer chips and other electronic devices.
    Silicon is a chemical element known as a 'metalloid' (because it has intermediate properties between a metal and a non-metal). It is used as a semiconductor, for example in microchips in computers, and to make photovoltaic cells for solar panels.
    Smart meter
    A smart meter is a more sophisticated version of your normal gas or electricity meter (in fact, a single smart meter may monitor both) that is linked to your energy provider and can also be linked to a computer in your home. Not yet available, it will eliminate the need for estimated bills, and allow you to monitor your own usage: which devices are using the most energy and when. Smart meters will generally also store up to a month of usage data.
    Smoke-free zone
    A smoke-free zone (or smokeless zone, or smoke control area) is not, in this context, anything to do with cigarettes. It refers to an area, designated by a local authority, where only authorised fuels - for example smokeless fuel, coke, and gas - may be burned. Other fuels may sometimes be permitted when used on specified authorised appliances. Ordinary coal, and wood (other than small amounts of kindling) are prohibited. The zones originated in London after legislation in 1946 in response to terrible smogs but are now very common in towns and cities nationwide.
    Solar energy
    Energy derived from the sun's rays.
    Solar panels
    Solar panels, usually roof-mounted, use the energy of the sun to generate electricity for home use, with the potential to sell surplus back to the grid. Light shining on a panel of photovoltaic cells creates an electric field across layers of semiconductive material, causing electricity to flow.
    Solar water heater
    A solar water heater uses the energy of the sun directly to heat a fluid that is fed into your hot water tank, meaning your boiler has less work to do (and requires less energy) to get your hot water to the required temperature.
    Standby, or 'sleep mode', is a mode in which electronic appliances are turned off but still drawing current and ready to activate on command. Although legislation has limited the energy new appliances can use in standby mode, they still use more energy than if they are switched off at the wall.
    Stern report
    The Stern report - or the Stern Review on the Economics of Climate Change - is a 700-page report, written by economist Sir Nicholas Stern for the UK government, and published in October 2006. It discusses the effect of climate change and global warming on the world economy and concludes that global warming could shrink the global economy by 20%, but that immediate action to combat it effectively would cost just 1% of global gross domestic product.
    The second lowest level of the atmosphere, extending from about 10km to about 50km altitude. The ozone layer, the part of the earth's atmosphere with the greatest concentration of ozone, forms part of the stratosphere. Because it sits above the troposphere, where most air turbulence occurs, the lower stratosphere is where most commercial airlines set their cruising altitude.
    Sustainability - whether applied to energy, technology, industry, agriculture or just consumption of resources in general - refers to the concept of using things at a rate that, while meeting our own needs, does not compromise future generations' ability to meet theirs. In environmental terms, a process or industry is unsustainable when it requires natural resources to be used up faster than they can be replenished.

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  18. T

    Textile banks
    A textile bank is a place to take old clothes for recycling. Compared with other materials such as glass, there is, as yet, very little textile recycling in the UK.
    A thermostat maintains the temperature of a system at or near a stipulated level using sensors that tell it when to turn off heating devices. In most household central heating systems, a wall-mounted thermostat is used to set a maximum temperature for the house, while thermostatic radiator valves can be used to set a desired level for individual radiators.
    Thermostatic radiator valves
    Thermostatic radiator valves (TRVs) automatically open and close as necessary to control the flow of hot water into a radiator and so achieve the pre-set air temperature for a particular room, rather than for the whole house. The level is set by turning a dial on the radiator.
    A toxin is a chemical compound from one organism that is harmful to another organism.
    The lowest level of the atmosphere, from the surface to about 10km. It is the level at which clouds form and where our weather phenomena occur.
    Turbulence describes irregular eddies of air within the general air current. It can be caused when wind flows over obstacles such as trees or buildings and gets 'churned up', so it no longer has a smooth flow. Wind turbines do not handle turbulence well and power production can be dramatically decreased.

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  19. U

    UK CO2 targets
    UK CO2 targets are this country's self-imposed goals for reducing carbon dioxide emissions, and go beyond the targets set out in the Kyoto protocol. The Climate Change Bill, which has been passed with amendments by the House of Lords but, as of summer 2008, is not yet law, stipulates a 60% reduction in emissions of CO2 by 2050 and an interim reduction of 26-32% by 2020. The figures are compared to a 1990 baseline. Once the Climate Change Bill is enacted, those targets (or any amendments to them) will become legally binding.

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  20. W

    Water meter
    A device used to measure the volume of water used by a household or business. Billing people for the water they actually use, rather than a fixed annual charge, is increasingly common in the UK, and is regarded as an incentive to users to avoid wasting water.
    Water pressure
    Water pressure is the force that pushes water through pipes and determines the rate of flow from your taps. Water companies are required to provide water at a pressure that will reach the upper floors of houses, but where this is a problem, pressure can be improved using pumps. However, devices such as power showers, which use a pump to boost flow for a more powerful shower spray, also greatly increase the volume of water used and the energy required to heat it.
    A watt is a unit of power. Power is the rate at which energy is used, and a watt is equal to a rate of one joule of energy per second. Watts are commonly used when referring to the energy consumption of relatively small things like lightbulbs, while kilowatts (a thousand watts) are used for larger machines. Megawatts (a million watts) are used to measure the electricity generation of power stations. See also kilowatt-hours.
    White goods
    A general term usually applied to major domestic electric appliances, such as fridges and washing machines.
    Wind turbine
    All turbines use kinetic (movement) energy to cause a bladed rotor to turn and so generate electricity. A wind turbine is a machine that captures the force of the wind. Often seen in remote, exposed coastal regions or offshore where wind speeds are greatest and most consistent, smaller versions can be installed on houses, but research suggests they may be useless, or even counter-productive, in urban settings.

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