Definitions are taken from the Intergovernmental Panel on Climate Change wherever possible. A list of sources is provided at the end of the glossary.

Terms in a definition that appear elsewhere in the glossary are italicised.

abatement. Activity that leads to a reduction in greenhouse gas emissions.

abrupt climate change. The nonlinearity of the climate system may lead to abrupt climate change. The term ‘abrupt’ often refers to time scales faster than the typical time scale of the responsible forcing.

adaptation. Adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities.

adaptive capacity. The ability of a system to adjust to climate change (including climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences.

additionality. Reduction in net emissions by sources or enhancement of removals by carbon sinks that is additional to the reduction that would occur in the absence of an incentive provided through a program.

aerosols. A collection of airborne solid or liquid particles, with a typical size between 0.01 and 10 micrometres (a millionth of a metre) that remain in the atmosphere for a relatively short time.

afforestation. Planting of new forests on lands that historically have not contained forests.

albedo. The amount of solar radiation reflected by a surface or object, often expressed as a percentage.

Annex B countries/parties. Industrialised countries and economies in transition countries listed in Annex B to the Kyoto Protocol that have emissions reductions targets for the period 2008–12.

Annex I countries/parties. Industrialised countries and economies in transition listed in Annex I to the United Nations Framework Convention on Climate Change. They include the 24 original OECD members, the countries of the European Union, and 14 countries with economies in transition.

anthropogenic. Resulting from or produced by human beings.

Bali Roadmap. The key decisions agreed at the 2007 Bali Climate Change Conference, charting the way for the UN negotiations on a post-2012 UN climate agreement.

base case. In the Review’s modelling, the evolution of the global and Australian economies and associated greenhouse gas emissions to the end of the 21st century taking into account the impacts of climate change.

biochar. A charcoal product made through anaerobic combustion of biomass (for example, farm or wood waste) at high temperatures.

biosequestration. The removal from the atmosphere and storage of greenhouse gases through biological processes, such as growing trees and practices that enhance soil carbon in agriculture.

business as usual. A scenario of future greenhouse gas emissions that assumes that there would be no major changes in policies on mitigation.

carbon budget. The amount of carbon (or emissions, expressed as carbon dioxide equivalent) allowed to be released over a number of years, by a given party or parties.

carbon–climate feedback. See feedback.

carbon cycle. The term used to describe the movement of carbon in various forms (for example, as carbon dioxide or methane) through the atmosphere, ocean, plants, animals and soils.

carbon dioxide equivalent (CO2-e). A measure that allows for the comparison of different greenhouse gases in terms of their global warming potential.

carbon dioxide equivalent concentration. The concentration of carbon dioxide (measured in parts per million) that would lead to the same amount of radiative forcing as a given mixture of carbon dioxide and other greenhouse gases.

carbon dioxide equivalent emissions. The amount of carbon dioxide emissions that would cause the same integrated radiative forcing, over a given time horizon, as an emitted amount of a well-mixed greenhouse gas. The equivalent carbon dioxide emission is obtained by multiplying the emission of a well-mixed greenhouse gas by its global warming potential for the given time period.

carbon dioxide fertilisation. Increasing plant growth or yield by elevated concentrations of atmospheric carbon dioxide.

carbon price. The price at which emissions permits can be traded, nationally or internationally.

carbon sink or reservoir. Parts of the carbon cycle that store carbon in various forms.

Clean Development Mechanism (CDM). A flexibility mechanism under the Kyoto Protocol that allows Annex I countries to meet part of their obligation to reduce emissions by undertaking approved emissions reduction projects in developing countries. Emissions reductions under the CDM can create tradable permits offset credits, called certified emission reductions or CERs.

climate change. A change in the state of the climate that can be identified (for example, by using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer.

climate sensitivity. A measure of the climate system’s response to sustained radiative forcing. Climate sensitivity is defined as the global average surface warming that will occur when the climate reaches equilibrium following a doubling of carbon dioxide concentrations.

climate system. A highly complex system consisting of the atmosphere, the water cycle, ice, snow and frozen ground, the land surface and plants and animals, and the interactions between them.

CO2-e. See carbon dioxide equivalent.

commitment period. The period in which Annex B countries are required to meet their emissions reduction commitments. The first commitment period is 2008 to 2012. The dates of the second commitment period have not yet been determined.

committed warming. Warming of the climate which, due to the thermal inertia of the ocean and slow processes in ice sheets, biological sinks and land surfaces, would continue even if the atmospheric composition were held fixed at today’s values.

contraction and convergence. A model for allocating a global emissions budget among nations. Allocations of emissions entitlements start at current emissions levels, and converge over time to equal per capita allocations in all countries. At the same time, the global emissions budget, and thus the global per capita average, contracts toward lower levels.

deforestation. Conversion of forest to non-forested land.

direct emissions. Emissions from sources within the boundary or control of an organisation’s or facility’s (or individual’s) processes or actions. They can include emissions from fuel combustion (for example, in transport) and non-combustion emissions arising from physical or chemical processes (for example, in agricultural production or industrial manufacturing).

ecosystem. A distinct system of interacting living organisms, together with their physical environment. The extent of an ecosystem may range from very small spatial scales to, ultimately, the entire earth.

El Niño – Southern Oscillation. A coupled fluctuation in the atmosphere and the equatorial Pacific Ocean that has a large influence on Australia’s climate.

emissions (or carbon) intensity. A measure of the amount of carbon dioxide, or other greenhouse gases, emitted per unit of, for example, electricity, energy output or kilometre of travel.

emissions limit or emissions cap. A limit on the number of tonnes of greenhouse gases that can be emitted under an emissions trading scheme. The limit could apply to the whole economy, or to the sectors covered under the scheme.

emissions permit. See permit.

emissions trading scheme. A market-based approach to reducing emissions. An emissions trading scheme places a limit on emissions allowed from all sectors covered by the scheme. It allows those reducing greenhouse gas emissions to use or trade excess emissions permits to offset emissions at another source. Also referred to as a ‘cap and trade scheme’.

energy efficiency. The ratio of energy required to produce a certain level of a service, such as kilowatt hours per unit of heat or light.

energy intensity. A measure of the amount of energy supplied or consumed per unit of, for example, gross domestic product or sales.

enteric fermentation. Part of the digestive process of ruminant animals, such as cows and sheep, that results in the release of methane.

evapotranspiration. The sum of evaporation and plant transpiration from the earth’s land surface to the atmosphere.

exposure. The nature and degree to which a system is exposed to significant climatic variations.

feedback. An interaction mechanism between processes, where the result of an initial process triggers changes in a second process and that in turn influences the initial one. A positive feedback intensifies the original process, and a negative feedback reduces it.

fluorinated gases. Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). See greenhouse gas.

forcing. An induced change to a system.

geo-engineering. Technological efforts to reduce global warming by stabilising the climate system through intervention in the energy balance of the earth.

geosequestration. Injection of carbon dioxide directly into underground geological formations.

global warming potential. The index used to translate the level of emissions of greenhouse gases into a common measure in order to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations.

greenhouse effect. The effect created by greenhouse gases in the earth’s atmosphere that allow short-wavelength (visible) solar radiation to reach the surface, but absorb the long-wavelength radiation that is reflected back, leading to a warming of the surface and lower atmosphere.

greenhouse gas. Any gas that absorbs infrared radiation in the atmosphere. This property causes the greenhouse effect. With the exception of Chapter 2, where a wider range of greenhouse gases are discussed, the term ‘greenhouse gases’ in this report relates to those gases covered by the Kyoto Protocol, which are carbon dioxide, nitrous oxide, methane, sulphur hexafluoride, perfluorocarbons (PFCs) and hydrofluorocarbons (CHFCs).

ice sheet. A mass of land ice that is sufficiently deep to cover most of the underlying bedrock, so that its shape is mainly determined by the flow of the ice as it deforms internally and/or slides at its base.

indirect emissions. Emissions that are a consequence of the activities of an organisation (or individual) but originate from sources owned or controlled by another. Indirect emissions can refer to the emissions attributable to the purchase of electricity, heat or steam from another party, and also from activities such as outsourcing and waste disposal.

intertemporal flexibility. The ability to use emissions permits at different points in time, made possible through the flexibility mechanisms of hoarding and lending.

Kyoto Protocol. An agreement adopted under the United Nations Framework Convention on Climate Change in 1997. It entered into force in 2005.

long-lived greenhouse gases. A term used to identify the selection of greenhouse gases covered by the Kyoto Protocol to distinguish them from ozone and water vapour, both of which are removed from the atmosphere relatively quickly.

long-wavelength radiation. Thermal radiation, or heat, emitted by the earth’s surface, the atmosphere and the clouds. It is also known as ‘infrared radiation’.

Marrakesh Accords. A series of agreements signed in Morocco in 2001 on the rules of meeting the targets set by the Kyoto Protocol.

mitigation. A reduction in the source of, or enhancement of the sinks for, greenhouse gases.

Montreal Protocol. The Montreal Protocol on Substances that Deplete the Ozone Layer, adopted in 1987. It controls the consumption and production of chemicals that destroy stratospheric ozone, such as chlorofluorocarbons.

offsets. Reductions or removals of greenhouse gas emissions that are used to counterbalance emissions elsewhere in the economy.

overshoot scenario or profile. A mitigation scenario where concentrations of a greenhouse gas (or a mix of greenhouse gases) peak at a higher atmospheric concentration than the eventual target, and then reduce over time to achieve stabilisation.

passenger-kilometre. A measure of passenger transport activity, equal to one passenger carried one kilometre. For example, two individuals in a car travelling 50 kilometres is equal to 100 passenger-kilometres.

peaking scenario or profile. A mitigation scenario where concentrations of a greenhouse gas (or a mix of greenhouse gases) stabilise or peak, and then continue to reduce.

permit or emissions permit. A certificate created under an emissions trading scheme that enables the holder to emit a specified amount of greenhouse gases, generally one tonne of carbon dioxide equivalent.

price ceiling. An upper limit on carbon prices. Once the price ceiling is reached, an unlimited amount of permits are issued at that price.

floor price. A lower limit on carbon prices. When the floor price is reached, authorities would intervene to reduce the supply of permits, in order to keep prices at or above the floor.

primary energy. Energy in the forms obtained directly from nature, for example coal, natural gas or solar energy.

radiative forcing. A measure of the influence that a factor has on the energy balance of the climate system. Positive forcing tends to warm the surface, while negative forcing tends to cool it.

reference case. In the Review’s modelling, the evolution of the global and Australian economies and associated greenhouse gas emissions to the end of the current century in the absence of climate change.

reforestation. Replanting of forests on lands that once contained forests but were converted to some other use.

secondary market. In the context of an emissions trading scheme, a financial market for trading of permits, whether by auction of some other method of allocation. It may also include markets in physical or financial contracts for the future purchase or sale of permits (forward contracts).

sensitivity. With respect to the climate system, the degree to which the system is affected, either adversely or beneficially, by climate-related stimuli. With respect to modelling, a sensitivity analysis may be used to assess how the variation of model assumptions affect the output of that model.

sequestration. Removal of carbon from the atmosphere by, and storage in, terrestrial or marine reservoirs.

severe weather event. An event that is rare within its statistical reference distribution at a particular place. The characteristics of what is called ‘severe weather’ may vary from place to place. An ‘extreme climate event’ is an average of a number of weather events over a certain period of time—an average that is itself extreme (for example, rainfall over a season).

sink. See carbon sink.

solar radiation. Electromagnetic radiation emitted by the sun. It is also referred to as ‘short-wavelength radiation’.

stabilisation. In the climate change context, keeping constant the atmospheric concentrations of one or more greenhouse gases (such as carbon dioxide) or of a carbon dioxide equivalent concentration of a mix of greenhouse gases.

storm surge. A temporary increase, at a particular location, in the height of the sea due to extreme meteorological conditions (low atmospheric pressure and/or strong winds). A storm surge is the excess above the level expected from the tidal variation alone at that time and place.

stratosphere. The highly stratified layer of the atmosphere above the troposphere extending from about 10 km (ranging from 9 km at high latitudes to 16 km in the tropics on average) to about 50 km in altitude.

sunspot cycle. Periods of high activity observed in numbers of sunspots (small dark areas on the sun), as well as radiative output, magnetic activity and emission of high-energy particles.

temperature reference point or baseline. Unless otherwise specified, temperature changes discussed in this report are expressed as the difference from the period 1980–99, expressed as ‘1990 levels’ in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. To compare temperature increases from 1990 levels to changes relative to pre-industrial levels, 0.5°C should be added.

thermal expansion. In connection with sea level, the increase in volume (and decrease in density) that results from warming water. A warming of the ocean leads to an expansion of the ocean volume and hence to sea-level rise.

thermohaline circulation. Large-scale circulation in the ocean driven by high densities at or near the surface, caused by cold temperatures and/or high salinities, in addition to mechanical forces such as wind and tides.

threshold or tipping point. The point in a system at which sudden or rapid change occurs, which may be irreversible.

tonne-kilometre. A measure of freight activity, equal to one tonne of freight carried one kilometre. For example, 20 tonnes carried 5 kilometres is equal to 100 tonne-kilometres.

trade-exposed, emissions-intensive industries. Industries with product prices that are set by world markets and that produce significant emissions during their production processes.

transaction costs. Costs associated with a market exchange (which may include indirect costs of market participation, such as information gathering).

transition countries. Countries in central and eastern Europe and the former Soviet Union defined in the United Nations Framework Convention on Climate Change and the Kyoto Protocol as ‘undergoing the process of transition to a market economy’.

troposphere. The lowest part of the atmosphere, from the surface to about 10 km in altitude at mid latitudes (ranging from 9 km at high latitudes to 16 km in the tropics on average), where clouds and weather phenomena occur.

ultraviolet radiation. The high-energy, invisible part of the spectrum of light emitted by the sun. The majority of ultraviolet radiation is absorbed by the layer of ozone in the stratosphere.

United Nations Framework Convention on Climate Change (UNFCCC). The international treaty that sets general goals and rules for confronting climate change. It has the goal of preventing ‘dangerous’ human interference with the climate system. Signed in 1992, it entered into force in 1994, and has been ratified by all major countries of the world.

upstream point of obligation. Designating the point of obligation at a point higher or earlier in the supply chain. For example, the obligation for emissions from petrol can be placed upstream at the point of excise tax collection.

utility. Personal satisfaction or benefit derived by individuals from the consumption of goods and services.

vector-borne disease. A disease that is transmitted between hosts by a vector organism (such as a mosquito or tick—for example, dengue virus).

volumetric control. The imposition of a restriction on the amount of something allowed. For example, a cap and trade emissions trading scheme sets a limit on the amount of emissions that may be released over a given period of time without incurring a penalty. By contrast, a price control policy would set the cost of emissions or permits, but not the amount.


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IPCC 2007, Climate Change 2007: Impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden & C.E. Hanson (eds), Cambridge University Press, Cambridge.

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