Glossary Terms: All | A-D | E-I | J-Q | R-Z |

Adaptation: Actions by individuals or systems to avoid, withstand, or take advantage of current and projected climate changes and impacts. Adaptation decreases a system’s vulnerability, or increases its resilience to impacts.

Adaptive Capacity: A system’s inherent ability to adapt to climate change impacts.

Aerosols: Solid or liquid particles suspended within the atmosphere (see "sulfate aerosols" and "black carbon aerosols").

Afforestation: Planting of new forests on lands that have not been recently forested.

Air Retarder: A material or structural element that inhibits airflow into and out of a building’s envelope or shell. It can be a house wrap, which reduces air infiltration and exfiltration yet allows water to easily diffuse through it. An air barrier is an assembly of materials and construction details that severely reduces air infiltration. (BSC/WAPTAC)

Air Sealing: Sealing penetrations in the walls, floor, and ceiling where outside air enters the home. It’s the most cost-effective way to improve the energy efficiency of a home. (PATH)

Albedo: Refers to the ratio of light from the sun that is reflected by the Earth’s surface to the light received by it. Unreflected light is converted to infrared radiation (i.e., heat), which causes atmospheric warming (see “radiative forcing”). Thus, surfaces with a high albedo (e.g., snow and ice) generally contribute to cooling, whereas surfaces with a low albedo (e.g., forests) generally contribute to warming. Changes in land use that significantly alter the characteristics of land surfaces can therefore influence the climate through changes in albedo.

Allowance: An authorization to emit a fixed amount of a pollutant.

Allocation: Under an emissions trading scheme, permits to emit can initially either be given away for free, usually under a ‘grandfathering’ approach based on past emissions in a base year or an ‘updating’ approach based on the more recent emissions. The alternative is to auction permits in an initial market offering.

Ancillary Benefits: Complementary benefits of a climate policy including improvements in local air quality and reduced reliance of imported fossil fuels.

Anthropogenic GHG Emissions: Emissions of greenhouse gasses resulting from human activities.

Appliance Age: If you did not purchase your appliance new or do not remember its date of purchase, you may contact a local dealer to find out how to determine the year model of your appliance. You may also be able to find the age of your appliance online by searching the web. Try here:

Assigned Amount: In the Kyoto Protocol, the permitted emissions, in CO2 equivalents, during a commitment period. It is calculated using the Quantified Emission Limitation and Reduction Commitment (QELRC), together with rules specifying how and what emissions are to be counted.

ATV: All Terrain Vehicle. A small, open, motorized vehicle with three or four wheels designed for recreational use.

Ballast: A device used to control the voltage in a fluorescent lamp. (EERE)

Barrel: A unit of volume equal to 42 U.S. gallons. One barrel weighs 306 pounds, or 5.80 million Btu of crude oil. Barrel is abbreviated as bbl.

Base Year: Targets for reducing GHG emissions are often defined in relation to a base year. In the Kyoto Protocol, 1990 is the base year for most countries for the major GHGs; 1995 can be used as the base year for some of the minor GHGs.

Baseload: For residential customers, the remaining energy consumption after the energy used for cooling and/or heating has been subtracted. It includes energy used for water heating, refrigeration, clothes dryer, lighting, electronics, etc. Baseload use is more or less constant each month, year round.

Baselines: The baseline estimates of population, GDP, energy use and hence resultant greenhouse gas emissions without climate policies, determine how big a reduction is required, and also what the impacts of climate change without policy will be.

Basket of Gases: This refers to the group six of greenhouse gases regulated under the Kyoto Protocol. They are listed in Annex A of the Kyoto Protocol and include: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).

Battery: An energy storage device made up of one or more electrolyte cells.

Biodiesel: An alternative fuel that can be made from any fat or vegetable oil. It can be used in any diesel engine with few or no modifications. Although biodiesel does not contain petroleum, it can be blended with diesel at any level or used in its pure form.

Biodiversity: The variety of organisms found within a specified geographic region.

Biofuel: Biomass that is converted directly into liquid fuels, usually in the form of ethanol or biodiesel. Biofuels: Liquid fuels and blending components produced from biomass (plant) feedstocks, used primarily for transportation.

Biogas: A mixture of methane and carbon dioxide produced by the bacterial decomposition of organic wastes and used as a fuel.

Biomass: Any organic (plant or animal) material that is available on a renewable basis, including agricultural crops and agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, and aquatic plants.

Black Carbon Aerosols: Particles of carbon in the atmosphere produced by inefficient combustion of fossil fuels or biomass. Black carbon aerosols absorb light from the sun, shading and cooling the Earth’s surface, but contribute to significant warming of the atmosphere (see “radiative forcing“).

Blower Door: A device used by energy auditors and raters to pressurize a building in order to locate places of air leakage and energy loss. (WAPTAC)

British Thermal Unit (Btu): A unit of heat energy. One Btu is the amount of energy needed to raise the temperature of one pound of water one degree Fahrenheit. Natural gas is sometimes billed in units of million Btus, which is also referred to as a decatherm (or dekatherm). One Btu is equal to 252 calories.

Bubble: An option in the Kyoto Protocol that allows a group of countries to meet their targets jointly by aggregating their total emissions. The member states of the European Union are utilizing this option.

Building Heat-Loss Factor: The measure of the heating requirements of a building expressed in BTU per degree-day. (EERE)

Capital Stock: Existing investments in energy plant and equipment that may or may not be modified once installed.

Carbon Capture and Storage (CCS): Carbon capture and storage (also referred to as carbon capture and sequestration) is a technique for trapping carbon dioxide as it is emitted from large point sources, compressing it, and transporting it to a suitable storage site where it is injected (sequestered) into the ground.

Carbon Dioxide (CO2): CO2 is a colorless, odorless, non-poisonous gas that is a normal part of the ambient air. Of the six greenhouse gases normally targeted, CO2 contributes the most to human-induced global warming. Human activities such as fossil fuel combustion and deforestation have increased atmospheric concentrations of CO2 by approximately 30 percent since the industrial revolution. CO2 is the standard used to determine the "global warming potentials" (GWPs) of other gases. CO2 has been assigned a 100-year GWP of 1 (i.e., the warming effects over a 100-year time frame relative to other gases).

Carbon Dioxide Equivalent (CO2e): Carbon Dioxide Equivalent (CO2e). The emissions of a gas, by weight, multiplied by its "global warming potential."

Carbon Footprint: The total set of greenhouse gas emissions caused directly and indirectly by an [individual, event, organization, product] expressed as CO2e.

Carbon Monoxide: A colorless, odorless, poisonous gas produced by incomplete fossil fuel combustion.

Carbon Sinks: Processes that remove more carbon dioxide from the atmosphere than they release. Both the terrestrial biosphere and oceans can act as carbon sinks.

Carbon Taxes: A surcharge on the carbon content of oil, coal, and gas that discourages the use of fossil fuels and aims to reduce carbon dioxide emissions.

Certified Emissions Reduction (CER): Reductions of greenhouse gases achieved by a Clean Development Mechanism (CDM) project. A CER can be sold or counted toward Annex I countries’ emissions commitments. Reductions must be additional to any that would otherwise occur.

Chemical Energy: Energy stored in a substance and released during a chemical reaction such as burning wood, coal, or oil.

Chimney (or Stack) Effect: The tendency of heated air or gas to rise in a duct or other vertical passage, such as in a chimney, small enclosure, or building, due to its lower density compared to the surrounding air or gas. (EERE)

Chlorofluorocarbons (CFCs): CFCs are synthetic industrial gases composed of chlorine, fluorine, and carbon. They have been used as refrigerants, aerosol propellants, cleaning solvents and in the manufacture of plastic foam. There are no natural sources of CFCs. CFCs have an atmospheric lifetime of decades to centuries, and they have 100-year "global warming potentials" thousands of times that of CO2, depending on the gas. In addition to being greenhouse gases, CFCs also contribute to ozone depletion in the stratosphere and are controlled under the Montreal Protocol.

Clean Development Mechanism (CDM): One of the three market mechanisms established by the Kyoto Protocol. The CDM is designed to promote sustainable development in developing countries and assist Annex I Parties in meeting their greenhouse gas emissions reduction commitments. It enables industrialized countries to invest in emission reduction projects in developing countries and to receive credits for reductions achieved.

Climate: The long-term average weather of a region including typical weather patterns, the frequency and intensity of storms, cold spells, and heat waves. Climate is not the same as weather.

Climate Change: Refers to changes in long-term trends in the average climate, such as changes in average temperatures. In IPCC usage, climate change refers to any change in climate over time, whether due to natural variability or as a result of human activity. In UNFCC usage, climate change refers to a change in climate that is attributable directly or indirectly to human activity that alters atmospheric composition.

Climate Sensitivity: The average global air surface temperature change resulting from a doubling of pre-industrial atmospheric CO2 concentrations. The IPCC estimates climate sensitivity at 1.5-4.5oC (2.7-8.1oF).

Climate Variability: Refers to changes in patterns, such as precipitation patterns, in the weather and climate.

Coal-Fired Power Plant: A power plant that uses coal as the fuel to generate electricity.

Cogeneration: The production of electrical energy and another form of useful energy (such as heat or steam) through the sequential use of energy.

Coke (coal): A solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents are driven off by baking in an oven at temperatures as high as 2,000 degrees Fahrenheit so that the fixed carbon and residual ash are fused together. Coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. Coke from coal is grey, hard, and porous and has a heating value of 24.8 million Btu per ton.

Colfiring: The process of burning natural gas in conjunction with another fuel to reduce air pollutants.

Combined Cycle: Characteristic of a power producing engine or plant that employs more than one thermodynamic cycle. Heat engines are only able to use a portion of the energy their fuel generates; the remaining heat from combustion is generally wasted. Combining two or more "cycles" results in improved overall efficiency.

Commitment Period: The period under the Kyoto Protocol during which Annex I Parties' GHG emissions, averaged over the period, must be within their emission targets. The first commitment period runs from January 1, 2008 to December 31, 2012.

Compact Fluorescent Light Bulb (CFL): A smaller version of standard fluorescent lamps that can directly replace standard incandescent lights. These lights consist of a gas-filled tube and magnetic or electronic ballast. The newer CFLs are vastly improved. They fit in most light fixtures and have warmer color tones and longer life. They will reduce the energy used by 75% over an incandescent bulb and last 6-10 years. (EERE/PATH)

Conference of the Parties (COP): The supreme decision-making body comprised of the parties that have ratified the UN Framework Convention on Climate Change. It meets on an annual basis. More than 190 government delegations are expected to attend the 14th COP in Poland in December 2008.

Convective Airflow: Air movement where less dense (warmer) air is displaced by more dense (cooler) air. Often expressed by the phrase “hot air rises.” Convective airflow can be useful if controlled, as in gravity hot-air heating systems, but is more often a contributor to heat loss. (WAPTAC)

Conventional Computer: A computer that has not received the ENERGY STAR rating.

Conventional Thermostat: A thermostat that does not have an ENERGY STAR rating and may have a mercury switch.

CRT: Cathode Ray Tube. A sealed tube in which electrons are emitted from a cathode to a phosphorescent screen to produce an image. Until several years ago, CRT displays were the most common type of displays used for televisions and desktop computer monitors.

Daily Peak: The greatest amount of electricity used during a certain period in a day, such as one hour, half hour, or quarter hour.

Decoupling: Separating a utility’s sales from its profits during rate adjustments, so the utility can still earn a profit when revenues go down as a result of energy efficiency programs. (ACI)

Discounting: The process that reduces future costs and benefits to reflect the time value of money and the common preference of consumption now rather than later.