Aerosols - microscopic particles originating from both natural sources (e.g., volcanoes) and human activities (e.g., coal burning).

Albedo - the reflectivity of Earth.

Alternative energy - energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).

Biofuel - gas or liquid fuel made from plant material (biomass). Includes wood, wood waste, wood liquors, peat, railroad ties, wood sludge, spent sulfite liquors, agricultural waste, straw, tires, fish oils, tall oil, sludge waste, waste alcohol, municipal solid waste, landfill gases, other waste, and ethanol blended into motor gasoline.

Biomass - technically, the total dry organic matter or stored energy content of living organisms in a given area. Biomass refers to forms of living matter (e.g., grasses, trees) or their derivatives (e.g., ethanol, timber, charcoal) that can be used as fuels.

Biomass energy - energy produced by combusting biomass materials such as wood. The carbon dioxide emitted from burning biomass will not increase total atmospheric carbon dioxide if this consumption is done on a sustainable basis (i.e., if in a given period of time, regrowth of biomass takes up as much carbon dioxide as is released from biomass combustion). Biomass energy is often suggested as a replacement for fossil fuel combustion.

Carbon cycle - general term used in reference to the sum of all reservoirs and flows of carbon on Earth. The flows tend to be cyclic in nature; for example, carbon removed from the atmosphere (one reservoir) and converted into plant tissue (another reservoir) is returned back into the atmosphere when the plant is burned.

Carbon reservoir or sink - within the carbon cycle, the physical site at which carbon is stored (e.g., atmosphere, oceans, Earth’s vegetation and soils, and fossil fuel deposits).

Carbon sequestration - The uptake and storage of carbon. Trees and plants, for example, absorb carbon dioxide, release the oxygen and store the carbon. Fossil fuels were at one time biomass and continue to store the carbon until burned. See also Carbon sinks.

Chlorocarbon - a compound containing chlorine and carbon; examples include carbon tetrachloride and methyl chloroform, both of which are ozone depleters.

Chlorofluorocarbons (CFCs) - compounds containing chlorine, flourine, and carbon; they generally are used as propellants, refrigerants, blowing agents (for producing foam), and solvents. They are identified with numbered suffixes (e.g., CFC-11, CFC-12) which identify the ratio of these elements in each compound. They are known to deplete stratospheric ozone and also are greenhouse gases in that they effectively absorb outgoing infrared radiation in the atmosphere.

Climate - the average weather together with its variability of representations of the weather conditions for a specified area during a specified time interval (usually decades).

Cogeneration - the simultaneous generation of both electric power and heat; the heat, instead of being discharged without further use, is used in some fashion (e.g., in district heating systems).

Deforestation - converting forest land to other vegetation or uses (e.g., cropland, pasture, dams).

Denitrification - microorganisms taking nitrogen out of its fixed form in the soil and putting it back into the atmosphere. Besides yielding molecular nitrogen (N2), denitrification produces nitrous oxide.

Emissions - flows of gases, liquid droplets or solid particles into the atmosphere. Gross emissions from a specific source are the total quantity released. Net emissions are gross emissions minus flows back to the original source. Plants, for example, take carbon from the atmosphere and store it as biomass during photosynthesis, and they release it during respiration, when they decompose, or when they are burned.

Fluorocarbon - a compound containing fluorine and carbon; among these are chlorinated flourocarbons (CFCs) and brominated fluorocarbons (halons).

Emission inventory - a list of air pollutants emitted into a community’s, a state’s, a nation’s, or Earth’s atmosphere in amounts per some unit time (e.g., day or year) by type of source. An emission inventory has both political and scientific applications.

Forest - terrestrial ecosystem (biome) with enough average annual precipitation (at least 76 centimeters or 30 inches) to support growth of various species of trees and smaller forms of vegetation.

Fossil fuel - coal, petroleum, or natural gas or any fuel derived from them.

Global warming - the apparent recent trend of increasing world-surface and tropospheric temperatures, thought to be caused by pollutants, and their “entrapment” of heat. This phenomenon is popularly known as “the greenhouse effect.”

Greenhouse effect - the effect produced as certain atmospheric gases allow incoming solar radiation to pass through to Earth’s surface, but prevent the outgoing (infrared) radiation, which is re-radiated from Earth, from escaping into outer space. The effect is responsible for warming the planet.

Greenhouse gas - any gas that absorbs infrared radiation in the atmosphere.

Hydrocarbon - a large class of organic chemicals made up of carbon atoms linked to hydrogen and, sometimes, oxygen. Hydrocarbons are used for fuel and other economically important materials. Hydrocarbons can be altered by the addition of other chemicals, such as halogens.

Ozone - a molecule consisting of three bound atoms of oxygen. Its chemical nomenclature is O3 . Most oxygen in the atmosphere, O2 , consists of only two oxygen atoms.

Ozone layer - something of a misnomer, since ozone does not occur in a flat “layer” in the atmosphere. This term refers to ozone in the stratosphere where it occurs in its highest concentrations - roughly from 1 to 10 parts per million. This atmospheric zone lies between 15 and 50 kilometers above Earth’s surface, depending upon latitude, season, and other factors.

Radiation - refers to electromagnetic energy, not to be confused with “radioactivity” (the emission of radiation, generally alpha or beta particles from the nucleus of an unstable isotope).

Stratosphere - the zone of the atmosphere between about 10-15 and 50 kilometers above Earth’s surface. Most of the ozone in the atmosphere is in the stratosphere. The stratosphere is separated from the troposphere below by a boundary layer called the tropopause.

Troposphere - the part of the atmosphere in which we live, ascending to about 15 km above Earth’s surface over which depth temperatures generally decrease with height. The atmospheric dynamics we know as “weather” take place within the troposphere.

Ultraviolet radiation - electromagnetic energy with frequencies higher than visible light or wavelengths shorter than visible light (less than 400 nm). Commonly abbreviated as “UV.”

This glossary was reproduced from the Climate Change Update from the National Safety Council’s Environmental Health Center (EHC) under a cooperative agreement with the U.S. Environmental Protection Agency. It is available on request. Write to Climate Change Update, Environmental Health Center, 1025 Connecticut Avenue, NW • Suite 1200, Washington, DC 20036, or e-mail ehc@nsc.org.