Glossary

Aerosol

An aerosol is a suspension of fine particles or droplets in the air. Atmospheric aerosols scatter and absorb sunlight, and affect the earth's heat balance by reflecting sunlight back into space and through indirect effects on cloud formation and atmospheric chemistry. Aerosols are produced from both natural and human processes such as volcanic eruptions, forest fires, desert dust storms, and burning of coal and oil.

Albedo

This is the proportion of light (or other forms of electromagnetic radiation, such as infrared) that is reflected off a surface. An ideal, perfectly reflective, white surface would have an albedo of 1.0. An albedo of 0.0 represents a perfectly absorptive, black, non-reflective surface. All real materials have albedos between 0 and 1.

Anthropogenic

Caused by human activity.

Biosphere

The biosphere is the earth's 'layer of life'—i.e. the regions of the planet on which life is found (or which are able to support life). It is concentrated on the surface of the planet (the land and the oceans) but also extends into the lower atmosphere and throughout the soil.

Carbon dioxide (CO2)

Carbon dioxide is a gas which presently makes up about 0.038 per cent of the earth's atmosphere. It is an important greenhouse gas. Even though its concentration in air is tiny, carbon dioxide is an essential natural component; without it, plant photosynthesis cannot take place.

Carbon sequestration

Carbon sequestration is the uptake or absorption of carbon, usually in the form of carbon dioxide. Major examples of carbon sequestration include uptake of carbon dioxide by growth of forests (through photosynthesis), and absorption of carbon dioxide by the oceans (through dissolution and chemical reactions).

Chlorofluorocarbons (CFCs)

Chlorofluorocarbons are compounds that contain carbon, fluorine and chlorine. Chlorofluorocarbons have been used as refrigerants, propellants and solvents. Their use has been banned by the Montreal Protocol on Substances that Deplete the Ozone Layer. They are also powerful greenhouse gases.

Common but differentiated responsibilities

In the Kyoto Protocol, the principles of equity and common but differentiated responsibilities and respective capabilities reflected the general acceptance by developed countries of their greater historical contribution to the accumulation of greenhouse gas emissions, in addition to their relatively greater resource capacity to develop and take remedial action. This leadership principle is reflected in the additional obligations imposed on Annex I countries.

Cryosphere

The cryosphere is the frozen part of the earth, including the polar ice sheets and sea ice; permafrost and other frozen ground; glaciers and ice caps; snow; and river and lake ice. The cryosphere plays a significant role in the earth's water cycle and heat balance.

Dalton Minimum

The Dalton Minimum was a period of low solar activity that began in the 1790s and ended in the 1820s. It is named after the English chemist, physicist and meteorologist, John Dalton, who first recorded it. It coincided with lower than average temperatures in the northern hemisphere.

Feedback mechanism

A means by which the outcome of a process affects the process itself, creating a loop. Positive feedback is when the loop leads to increased output or a reinforced tendency, whereas negative feedback leads to a reduced output or tends to dampen a tendency.

Foam blowing

Blowing of foam for products such as insulation in refrigerators, insulation for roofing and walls, foam furniture and bedding, car steering wheels and dashboards, packaging, and buoyancy devices. These products require the use of foam blowing agents, which have in the past included ozone-depleting substances such as chlorofluorocarbons. Foam blowing agents also tend to be strong greenhouse gases.

Greenhouse gases

Greenhouse gases are gases that contribute to the greenhouse effect in the earth's atmosphere. They are essentially transparent to incoming sunlight, but absorb heat radiated from the earth's surface, trapping this heat in the atmosphere and causing the atmosphere and earth's surface to maintain a warmer temperature than would be the case in the absence of these gases. The main greenhouse gases are water vapour and carbon dioxide. Carbon dioxide, methane and nitrous oxide are the main greenhouse gases that are increasing due to human activities.

Halocarbons

Halocarbons are chemical compounds which are similar to hydrocarbons but have halogen atoms in place of the hydrocarbon's hydrogen atoms. Halogens include fluorine, chlorine, bromine and iodine. Halocarbons are used, among other things, as refrigerants and pesticides.

Hydrocarbons

Hydrocarbons are chemical molecules which consist solely of carbon and hydrogen atoms. Examples include the simplest hydrocarbon—the gas methane (CH4). Methane is one carbon atom surrounded by four hydrogen atoms. Oil is a complex mixture of hydrocarbons. Burning hydrocarbons releases energy and also produces carbon dioxide.

Hydrochlorofluorocarbons (HCFCs)

Hydrochlorofluorocarbons are compounds containing hydrogen, carbon, fluorine and chlorine. They are being used to replace chlorofluorocarbons, but are subject to caps in their production and consumption, and a phase-out schedule. They contain chlorine and thus are an ozone-depleting substance, but to a much lesser extent than chlorofluorocarbons. They are also a strong greenhouse gas.

Hydrofluorocarbons (HFCs)

Hydrofluorocarbons are molecules containing solely carbon, hydrogen and fluorine. These synthetic molecules are up to 14000 times more powerful than carbon dioxide as greenhouse gases over a 100-year time frame.

Hydrofluoroethers (HFEs)

Hydrofluoroethers, otherwise known as fluorinated ethers, are chemical compounds that consist of an ether group (an oxygen atom connecting two hydrocarbon chains) with fluorine atoms attached.

Intergenerational equity

The principle of intergenerational equity provides that 'the Parties should protect the climate system for the benefit of present and future generations of humankind on the basis of equity and common but differentiated responsibilities and respective capabilities'.

IPCC

Intergovernmental Panel on Climate Change. The IPCC was established in 1988 to provide a comprehensive, objective, open and transparent assessment of the latest scientific, technical and socio-economic literature produced worldwide relevant to climate change and its risks and impacts, and options for mitigation and adaptation.

Isostatic

Isostatic refers to the state of equilibrium of the earth's crust between forces tending to elevate the crust and forces tending to depress the crust. Post-glacial rebound represents an example of isostatic forces acting when the load presented by ice masses on the land is removed as the ice melts, and the earth's crust rebounds to a new equilibrium level. This movement is slow, and post-glacial rebound from the last ice age is still occurring.

Little Ice Ages

The Little Ice Ages refer to periods in history when cooler than average temperatures were experienced for several decades at a time. The main such period was from about 1650, with another cool period from about 1770. The lower temperatures were thought to be caused by a combination of lower solar output and volcanic eruptions releasing aerosols that reflected sunlight into space. It is unclear whether the Little Ice Ages were a global phenomenon, since evidence comes predominantly from Europe. The cool periods did not last long enough to cause ice sheets to enlarge, though there were increases in glacial ice.

Maunder Minimum

The Maunder Minimum is the period between about 1645 and 1715, when the astronomer Edward Maunder observed that there were very few sunspots on the surface of the sun. This correlated with a cooler than average period in the northern hemisphere.

Medieval Warm Period

The Medieval Warm Period was a period during Medieval times from about 800–1300 AD when unusually warm temperatures were experienced in Europe. Available evidence suggests this was probably not the case in the rest of the world.

Methane (CH4)

Methane is the main component of natural gas; it is a powerful greenhouse gas with 25 times the warming effect of carbon dioxide over a 100-year time scale.

Mitigation

Mitigation of climate change refers to those responses that reduce the sources of greenhouse gases or enhance their sinks, thereby slowing climate change.

Neotectonism

Neotectonism refers to recent tectonic activity, occurring within Quaternary period (~2 million years ago to present) and Tertiary period (~65 to 2 million years ago). Tectonism is the motion and deformation of the earth's crust due to movement of continental and oceanic plates and volcanic activity.

Nitrous oxide

Nitrous oxide is a colourless, non-flammable gas; it is a powerful greenhouse gas with 298 times the warming potential of carbon dioxide over a 100-year time scale.

Ozone

Ozone is a molecule which consists of three atoms of oxygen. It is toxic to animals and plants, and damages human respiratory systems. In the lower atmosphere it is a pollutant produced from emissions of other compounds during fuel combustion. However, ozone in the upper atmosphere occurs naturally and acts to reduce the amount of dangerous ultraviolet radiation reaching the earth's surface.

Palaeoclimate

The climate in the geological past over the full history of the earth.

Particulates

Particulates are small solid or liquid particles that are suspended in the air. They are produced from natural and human processes including volcanic eruptions, dust storms, and combustion of coal and oil products.

Perfluorocarbons (PFCs)

Perfluorocarbons are compounds consisting of carbon and fluorine. They do not deplete the ozone layer but are very strong greenhouse gases with long lifetimes in the atmosphere.

pH

pH is a measure of the acidity of a solution, specifically the activity of dissolved hydrogen ions. The pH scale ranges from 0 to 14. Solutions with a pH less than 7 are acidic, while solutions with a pH greater than 7 are basic, or alkaline. A solution with a pH of 7 is neutral.

Precautionary principle

In the Kyoto Protocol, the precautionary principle states that 'where there are threats of serious or irreversible environmental damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation'. However, it is envisaged that such measures 'should be cost-effective so as to ensure global benefits at the lowest possible cost'.

Radiative balance

Radiative balance refers to the balance between incoming and outgoing electromagnetic radiation. The earth's radiative balance is a balance between solar radiation absorbed by the earth's surface, longwave (infrared) radiation emitted from the surface, and longwave radiation re-emitted from the atmosphere to the surface.

Radiative forcing

Radiative forcing refers to the influence on the earth's climate of various radiative components. These components include the amount of solar radiation reaching the atmosphere and the earth's surface, as well as the influence of individual greenhouse gases within the atmosphere and their relative contribution to radiative forcing (their warming contribution) through their ability to absorb longwave radiation emitted from the earth's surface.

Respective capabilities

In the Kyoto Protocol, the principles of equity and common but differentiated responsibilities and respective capabilities reflected the general acceptance by developed countries of their greater historical contribution to the accumulation of greenhouse gas emissions, in addition to their relatively greater resource capacity to develop and take remedial action. This leadership principle is reflected in the additional obligations imposed on Annex I countries.

Sink

A sink refers to a carbon sink or greenhouse gas sink, or a mechanism of uptake of carbon or other greenhouse gases, e.g. in the form of carbon dioxide. Examples include photosynthesis of vegetation, and absorption of carbon dioxide by the oceans.

Source

A source refers to a carbon source or greenhouse gas source, or a mechanism of release of greenhouse gases. Examples include burning of coal, oil and gas and biomass burning.

Stratosphere, stratospheric

The stratosphere is the upper atmosphere, above normal clouds, where temperature does not decline with altitude. This contrasts with the troposphere, or lower atmosphere, where clouds form and temperature falls with increasing altitude. The stratosphere is more stable than the troposphere, with less vertical mixing of air. The height of the stratosphere varies, starting at about 8 kilometres above the surface over the poles and at about 16 kilometres above the surface over the equator. The stratosphere extends up to about 50 kilometres in height. The concentration of ozone peaks in the stratosphere.

Sublimation

When a substance changes directly from a solid state to a gas, without passing through the liquid state (or the reverse process of changing directly from gas to solid). A well-known example of a substance which sublimates is dry ice, or frozen carbon dioxide, which at room temperatures changes from a solid to gas without becoming liquid during the process: hence 'dry' ice.

Sulphur hexafluoride (SF6)

Sulphur hexafluoride is a compound consisting of a sulphur atom and six fluorine atoms. It is a powerful greenhouse gas and is regulated under the Kyoto Protocol.

Tectonics

Tectonics refers to the motion and deformation of the earth's crust due to movement of continental and oceanic plates and volcanic activity.

Troposphere, tropospheric

The troposphere is the lowest portion of earth's atmosphere. The troposphere extends from the surface upwards, to an altitude of about 8 kilometres over the poles, and to about 16 kilometres over the equator. It contains three-quarters of the atmosphere's mass. Temperature falls with increasing altitude within the troposphere, which is in contrast to the situation in the stratosphere. The continuous movement of air within the troposphere (and the cooling as air rises) creates clouds and rain; thus the troposphere is the layer where most of the world's weather takes place.