Theme commentary
Tom Beer, Michael Borgas, Willem Bouma, Paul Fraser, Paul Holper and Simon Torok
CSIRO Atmospheric Research
prepared for the 2006 Australian State of the Environment Committee, 2006


a suspension of particles, other than water or ice, in the atmosphere and ranging in size from approximately five nanometres to larger than ten microns in radius; may be either natural or caused by human activity and most of the latter are usually considered to be pollutants.
air quality NEPM
National Environment Protection Measure for Ambient Air Quality.
air pollutant
any substance in air that could, in high enough concentrations, harm humans, animals, vegetation or material.
air toxics
gaseous, aerosol or particulate pollutants other than the six criteria pollutants (see criteria pollutants) which are present in the air in low concentrations with characteristics such as toxicity or persistence so as to be a hazard to human, plant or animal life.
a body of air bounded by topography and meteorology in which a contaminant, once emitted, is contained for a reasonable period of time.
ambient air
surrounding outdoor air.
of human origin or human induced.
atmospheric inversion
a condition occurring when a cool layer of air gets trapped below a layer of warm air and is unable to rise. This 'ceiling' leads to a build up of polluted air close to the ground and prevents vertical mixing and dispersion of smoke and other air pollutants.
background air quality
the naturally occurring mixture of air in the absence of anthropogenic sources and extreme events.
a toxic and carcinogenic air pollutant that is used as a solvent but is also emitted from a broad range of combustion sources, including motor vehicles and woodheaters.
biogenic emissions
emissions from natural sources including vegetation, soils and the ocean.
biomass burning
the combustion of organic waste matter, burning in slash-and-burn cultivation, fuel-wood use and land clearing through forest burning.
the collective name for living organisms on the planet.
carbon accounting
issues associated with measuring, calculating and valuing the relative benefits of greenhouse gas mitigation measures
carbon dioxide equivalent
an atmospheric carbon dioxide concentration that would have the same global radiative forcing effect as all of the human-produced greenhouse gases combined.
carbon sequestration
the uptake and storage of carbon.
carbon sink
a pool (reservoir) that absorbs or takes up released carbon from another part of the carbon cycle.
a substance or activity that causes cancer.
a substance that changes the rate at which a chemical reaction takes place without taking part in the reaction itself.
CFCs (chlorofluorocarbons)
synthetic products, which do not occur naturally and contain chlorine and fluorine; commonly used in various industrial processes and as refrigerants and, prior to 1990, as a propellant gas for sprays; deplete ozone in the stratosphere and are powerful greenhouse gases.
the average weather conditions of a place or region throughout the seasons.
climate variability
the natural year-to-year and season-to-season variation of the climate system.
criteria pollutants
air pollutants traditionally regarded as important in urban air—sulphur dioxide, carbon monoxide, nitrogen dioxide, ozone, particulate matter and lead (particulate and vapours).
El Niño
an extensive warming of the central and eastern Pacific that leads to a major shift in weather patterns across the Pacific. In Australia (particularly eastern Australia), El Niño events are associated with an increased probability of drier conditions.
enhanced greenhouse effect
the addition to the natural greenhouse effect resulting from human activities such as the burning of fossil fuels and land clearing, which increase the atmospheric levels of greenhouse gases such as carbon dioxide, methane, nitrous oxide, ozone and CFCs; see greenhouse effect.
ENSO (El Niño–Southern Oscillation)
a term given to year-to-year variability in the atmosphere and ocean centred in the tropical Pacific Ocean, encompassing El Niño events. The Southern Oscillation refers to changes in air pressure gradients across the Pacific Ocean; see El Niño.
fossil fuel
any hydrocarbon deposit that can be burned for heat or power, such as coal, oil and natural gas; produces carbon dioxide when burnt.
fugitive emissions
these are greenhouse gases or air pollutants that are emitted in an uncontrolled manner.
greenhouse effect
a term used to describe the role of atmospheric trace gases - water vapour, carbon dioxide, methane, nitrous oxide, ozone, in keeping the earth's surface warmer than it would be otherwise; see enhanced greenhouse effect.
greenhouse gases
those gases that, by affecting the radiation transfer through the atmosphere, contribute to the greenhouse effect.
halons include bromofluorocarbons and bromochlorofluorocarbons, which are very stable chemicals that are involved in ozone depletion in a similar manner to CFCs.
the presence of very small airborne particles in concentrations large enough to impede vision.
HCFCs (hydrochlorofluorocarbons)
chemicals used as interim replacements for CFCs, largely as refrigerants.
an organic molecule containing hydrogen and carbon; the major components of petroleum.
Kyoto Protocol
A protocol adopted by the supreme body of the UNFCCC in Kyoto, Japan, in 1997, committing Annex B countries (most OECD and some others) to limit or reduce anthropogenic greenhouse gas emissions relative to 1990 levels. The Kyoto protocol deals with carbon dioxide, nitrous oxide, methane, sulphur hexafluoride, hydrofluorocarbons and perfluorocarbons.
Montreal Protocol
An international agreement adopted in Montreal, Canada, in 1987 to regulate the production and use of chemicals containing chlorine and bromine, which deplete stratospheric ozone.
the proportion of sickness in a locality.
relative frequency of death, or death rate.
ozone depletion
the process whereby the natural equilibrium between chemical reactions forming and destroying stratospheric ozone is disturbed by the release of manufactured chemicals.
ozone layer
a region in the stratosphere where there is ozone.
microscopic or submicroscopic solid or liquid matter, such as soot, dust or smoke.
photochemical smog
air pollution caused by chemical reactions among various substances and pollutants in the atmosphere in the presence of sunlight; ozone is a major constituent.
a process whereby sunlight causes the chemical bonds in a molecule to break.
processes or places that remove or store gases, solutes or solids in accumulating parts of the environment.
the term comes from a combination of smoke and fog. However, in Australia most smog arises from chemical reactions between oxides of nitrogen and gaseous volatile organic compounds that take place in the presence of sunlight. see photochemical smog.
region of the atmosphere about 15 to 50 kilometres above the Earth's surface where the temperature typically changes little or increases with height; the ozone layer occurs in the stratosphere.
the lower layer of the atmosphere extending to about 15 kilometres above the Earth's surface where the temperature typically decreases with height; nearly all clouds form and weather processes are found in this region.
ultraviolet (UV) radiation
electromagnetic radiation of higher frequencies and shorter wavelengths than visible light; UV radiation is divided into three ranges: UV-A (320–400 nm), UV-B (280–320 nm) and UV-C (40–290 nm).
volatile organic compound
carbon containing compounds occurring in ambient air as gases or vapour with boiling points between 50°C and 260°C. The volatile organic compounds that participate in smog formation reactions are called reactive organic compounds. Examples of volatile organic compounds include benzene, xylene and toluene.