A reduction in atmospheric greenhouse gases through emissions avoidance or removal and sequestration of carbon from the atmosphere.

Australian Carbon Credit Unit (ACCU)

One Australian carbon credit unit represents one tonne of verified carbon dioxide equivalent abatement. ACCUs are created from eligible offsets projects and issued by the Clean Energy Regulator in accordance with section 147 of the Carbon Credits (Carbon Farming Initiative) Act 2011 (CFI Act).

ACCU Scheme

An Australian Government scheme that offers landholders, communities and businesses the opportunity to run projects in Australia that avoid the release of greenhouse gas emissions or remove and sequester carbon from the atmosphere. It is enacted through the  Carbon Credits (Carbon Farming Initiative) Act 2011(Opens in a new tab/window) and the Carbon Credits (Carbon Farming Initiative) Rule 2015(Opens in a new tab/window).

ACCU Project

Eligible offsets projects registered under the ACCU Scheme.


In human systems, the process of adjustment to actual or expected climate and its effects, in order to moderate harm or exploit beneficial opportunities. In natural systems, the process of adjustment to actual climate and its effects; human intervention may facilitate adjustment to expected climate

Adaptation assessment

The practice of identifying options to adapt to climate change and evaluating them in terms of criteria such as availability, benefits, costs, effectiveness, efficiency, and feasibility.

Adaptive capacity

The combination of the strengths, attributes, and resources available to an individual, community, society, or organisation that can be used to prepare for and undertake actions to reduce adverse impacts, moderate harm, or exploit beneficial opportunities.


A collection of airborne solid or liquid particles, with a typical size between 0.01 and 10μm, that reside in the atmosphere for at least several hours. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in several ways: directly through scattering and absorbing radiation, and indirectly by acting as cloud condensation nuclei or modifying the optical properties and lifetime of clouds.


The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Snow-covered surfaces have a high albedo, the surface albedo of soils ranges from high to low, and vegetation covered surfaces and oceans have a low albedo. The Earth’s planetary albedo varies mainly through varying cloudiness, snow, ice, leaf area, and land cover changes.

Anthropogenic emissions

Emissions of greenhouse gases, greenhouse gas precursors, and aerosols associated with human activities. These activities include the burning of fossil fuels, deforestation, land use changes, livestock, fertilisation, etc., that result in a net increase in emissions.

Article 6

Article 6 of the Paris Agreement establishes a framework for international cooperation of countries to reduce emissions and meet their nationally determined contributions.

Atlantic Multi-decadal Oscillation (AMO)

A multi-decadal (65- to 75-year) fluctuation in the North Atlantic, in which sea surface temperatures showed warm phases during roughly 1860 to 1880 and 1930 to 1960 and cool phases during 1905 to 1925 and 1970 to 1990 with a range of the order of 0.4°C.


The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium, and radiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio) and ozone. In addition, the atmosphere contains the greenhouse gas water vapor, whose amounts are highly variable but typically around 1% volume mixing ratio. The atmosphere also contains clouds and aerosols.


The process of establishing the most likely causes for the detected climate change or extreme weather event with a defined level of confidence.

Authority members

The authority comprises eight part-time members (including the Chair) and the Chief Scientist (ex officio). Members are appointed by the Minister responsible for climate change under s. 18 of the Climate Change Authority Act 2011.

Biological sequestration approaches

Human-induced activities that take advantage of natural biological systems to capture and store atmospheric carbon dioxide in living biomass, dead organic matter, soil and in aquatic environments.

Built environment

The built environment is the human-made surroundings where people gather to live, work and play. It encompasses both the physical structures where people do these activities and the supporting infrastructures, such as transport, water and energy networks.

Carbon capture and storage (CCS)

A process in which a relatively pure stream of carbon dioxide from industrial or energy related sources is separated (captured), conditioned, compressed and transported to a (usually geological) storage location for long-term isolation from the atmosphere.

Carbon capture and use (CCU)

A process in which carbon dioxide is captured and the carbon then used in a product. The climate effect of CCU depends on the product lifetime, the product it displaces, and the carbon dioxide source (fossil, biomass or atmosphere).

Carbon capture, use and storage (CCUS)

Processes in which carbon dioxide is captured and then either the carbon dioxide is transported to a storage location for long-term isolation from the atmosphere or the carbon is used in a product.

Carbon credit

A tradable unit that represents one tonne of greenhouse gas equivalent abatement.

Carbon cycle

The term used to describe the flow of carbon (in various forms, e.g., as carbon dioxide) through the atmosphere, ocean, terrestrial biosphere, and lithosphere.

Carbon dioxide (CO2)

A naturally occurring gas fixed by photosynthesis into organic matter. A byproduct of fossil fuel combustion and biomass burning, it is also emitted from land use changes and other industrial processes. It is the principal anthropogenic greenhouse gas that affects the Earth’s radiative balance.

Carbon dioxide equivalent (CO2-e)

The amount of carbon dioxide emission that would have an equivalent effect on a specified key measure of climate change, over a specified time horizon, as an amount of another greenhouse gas or a mixture of other greenhouse gases.

Carbon dioxide removal (CDR)

Anthropogenic activities removing carbon dioxide from the atmosphere and durably storing it in geological, terrestrial or oceanic reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical carbon dioxide sinks and direct air carbon dioxide capture and storage but excludes natural carbon dioxide uptake not directly caused by human activities.

Carbon Farming

The process of changing agricultural practices or land use to increase the amount of carbon stored in the soil and vegetation (sequestration) and to reduce greenhouse gas emissions from livestock, soil or vegetation (avoidance).

Carbon Farming Initiative

The Australian carbon crediting scheme first created by the Carbon Credits (Carbon Farming Initiative) Act 2011, since renamed (see ACCU Scheme).

Carbon leakage

The effects of policies that result in a displacement of the environmental impact, thereby counteracting the intended effects of the initial policies.

Carbon neutrality

Having a balance between emissions and absorption of greenhouse gases from the atmosphere.

Carbon Offset

A type of carbon credit that represents a reduction in emissions – whether prevented from entering the atmosphere or removed from the atmosphere – that is used to compensate for emissions that occur elsewhere.

Carbon sequestration

The process of storing carbon in a carbon pool, such as plants, soils, geologic formations and the ocean.


An area that collects and drains precipitation.

Clausius-Clapeyron relationship (or equation)

A relationship that in the context of weather and climate refers to the ability of air to hold water vapour, namely that warmer air can hold more water vapour.

Clean Energy Regulator

A Commonwealth statutory authority that administers regulatory schemes relating to clean energy, including the Renewable Energy Target, the Carbon Pricing Mechanism (now repealed), the National Greenhouse and Energy Reporting scheme, the Carbon Farming Initiative and the Emissions Reduction Fund.


Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system.

Climate change

A change in the state of the climate that can be identified (e.g., 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 change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.

Climate Change Authority

A Commonwealth statutory authority established on 1 July 2012 to provide independent advice on climate change policies to the minister responsible for climate change and to the parliament.

Climate extreme (extreme weather or climate event)

The occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable. For simplicity, both extreme weather events and extreme climate events are referred to collectively as ‘climate extremes.’ The full definition is provided in Section 3.1.2.

Climate feedback

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

Climate model

A numerical representation of the climate system that is based on the physical, chemical, and biological properties of its components, their interactions, and feedback processes, and that accounts for all or some of its known properties. The climate system can be represented by models of varying complexity, that is, for any one component or combination of components a spectrum or hierarchy of models can be identified, differing in such aspects as the number of spatial dimensions, the extent to which physical, chemical, or biological processes are explicitly represented, or the level at which empirical parameterizations are involved. Coupled Atmosphere-Ocean Global Climate Models (AOGCMs), also referred to as Atmosphere-Ocean General Circulation Models, provide a representation of the climate system that is near the most comprehensive end of the spectrum currently available. There is an evolution toward more complex models with interactive chemistry and biology. Climate models are applied as a research tool to study and simulate the climate, and for operational purposes, including monthly, seasonal, and interannual climate predictions.

Climate projection

A projection of the response of the climate system to emissions or concentration scenarios of greenhouse gases and aerosols, or radiative forcing scenarios, often based upon simulations by climate models. Climate projections are distinguished from climate predictions in order to emphasise that climate projections depend upon the emission/ concentration/radiative-forcing scenario used, which are based on assumptions concerning, e.g., future socioeconomic and technological developments that may or may not be realised and are therefore subject to substantial uncertainty.

Climate scenario

A plausible and often simplified representation of the future climate, based on an internally consistent set of climatological relationships that has been constructed for explicit use in investigating the potential consequences of anthropogenic climate change, often serving as input to impact models. Climate projections often serve as the raw material for constructing climate scenarios, but climate scenarios usually require additional information such as about the observed current climate.

Climate system

The climate system is the highly complex system consisting of five major components: the atmosphere, the oceans, the cryosphere, the land surface, the biosphere, and the interactions between them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations, and anthropogenic forcings such as the changing composition of the atmosphere and land use change.

Climate threshold

A critical limit within the climate system that induces a non-linear response to a given forcing.

Climate variability

Climate variability refers to variations in the mean state and other statistics (such as standard deviations, the occurrence of extremes, etc.) of the climate at all spatial and temporal scales beyond that of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability), or to variations in natural or anthropogenic external forcing (external variability).

Cold days/cold nights

Days where maximum temperature, or nights where minimum temperature, falls below the 10th percentile, where the respective temperature distributions are generally defined with respect to the 1961-1990 reference period


Confidence in the validity of a finding, based on the type, amount, quality, and consistency of evidence and on the degree of agreement. Confidence is expressed qualitatively.

Control run

A model run carried out to provide a ‘baseline’ for comparison with climate change experiments. The control run uses constant values for the radiative forcing due to greenhouse gases and anthropogenic aerosols appropriate to pre-industrial conditions.


Vertical motion driven by buoyancy forces arising from static instability, usually caused by near-surface cooling or increases in salinity in the case of the ocean and near-surface warming in the case of the atmosphere. At the location of convection, the horizontal scale is approximately the same as the vertical scale, as opposed to the large contrast between these scales in the general circulation. The net vertical mass transport is usually much smaller than the upward and downward exchange.

Counterbalance (of emissions)

The act of balancing out greenhouse gas emissions from one activity with the removal of emissions from the atmosphere via CDR. This can occur at the national, sub-national, corporate and facility scale.

Crediting period

In relation to a carbon crediting project, for example an ACCU project, the crediting period is the length of time the project is eligible to be issued carbon credits.

Detection and attribution

Climate varies continually on all time scales. Detection of climate change is the process of demonstrating that climate has changed in some defined statistical sense, without providing a reason for that change. Attribution of causes of climate change is the process of establishing the most likely causes for the detected change with some defined level of confidence.

Direct Air Capture

The separation of carbon dioxide from air and its preparation for storage or utilisation in processes or products.

Disaster management

Social processes for designing, implementing, and evaluating strategies, policies, and measures that promote and improve disaster preparedness, response, and recovery practices at different organizational and societal levels

Disaster risk

The likelihood over a specified time period of severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery.

Disaster risk management (DRM)

Processes for designing, implementing, and evaluating strategies, policies, and measures to improve the understanding of disaster risk, foster disaster risk reduction and transfer, and promote continuous improvement in disaster preparedness, response, and recovery practices, with the explicit purpose of increasing human security, well-being, quality of life, and sustainable development.

Disaster risk reduction (DRR)

Denotes both a policy goal or objective, and the strategic and instrumental measures employed for anticipating future disaster risk; reducing existing exposure, hazard, or vulnerability; and improving resilience.

Diurnal temperature range

The difference between the maximum and minimum temperature during a 24-hour period.

Double counting

One tonne of abatement is used to compensate for more than one tonne of emissions.


Downscaling is a method that derives local- to regional-scale (up to 100 km) information from larger-scale models or data analyses.


The capacity of a carbon stock to resist degradation or loss of carbon due to factors including environmental changes, human activities, and other natural disturbances.

Early warning system

The set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities, and organizations threatened by a hazard to prepare and to act appropriately and in sufficient time to reduce the possibility of harm or loss

El Niño-Southern Oscillation (ENSO)

The term El Niño was initially used to describe a warm-water current that periodically flows along the coast of Ecuador and Peru, disrupting the local fishery. It has since become identified with a basin-wide warming of the tropical Pacific Ocean east of the dateline. This oceanic event is associated with a fluctuation of a global-scale tropical and subtropical surface pressure pattern called the Southern Oscillation. This coupled atmosphere-ocean phenomenon, with preferred time scales of 2 to about 7 years, is collectively known as the El Niño-Southern Oscillation. It is often measured by the surface pressure anomaly difference between Darwin and Tahiti and the sea surface temperatures in the central and eastern equatorial Pacific. During an ENSO event, the prevailing trade winds weaken, reducing upwelling and altering ocean currents such that the sea surface temperatures warm, further weakening the trade winds. This event has a great impact on the wind, sea surface temperature, and precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific region and in many other parts of the world, through global teleconnections. The cold phase of ENSO is called La Niña.

Emissions budget

A cumulative amount of greenhouse gas emissions (usually measured as carbon dioxide equivalent) that can be emitted over a set period, e.g. 4,000 Mt CO2-e from 2021 – 2030, in order to achieve a chosen probability of keeping global warming under a specified limit

Emissions intensity

A measure of the amount of emissions associated with a unit of output—for example, emissions per unit of gross domestic product or electricity production.

Emissions reduction

Reducing the emissions from an activity, such as through energy efficiency improvements.

Emissions Reduction Fund

A scheme resulting from the expansion of, streamlining and other changes to the Carbon Credits (Carbon Farming Initiative) Act 2011, in December 2014. The ERF involves purchases of ACCUs by the Government. The scheme has since been renamed (see ACCU Scheme).

Emissions reduction target

Australia’s goal for national emissions.

Emissions removal

The withdrawal of greenhouse gases from the atmosphere as a result of deliberate human activities. These include enhancing biological sinks and using chemical engineering to achieve long-term removal storage. Also called ‘anthropogenic removals’ and ‘greenhouse gas removal’.

Emissions unit

Represents a unit of one metric tonne of carbon dioxide equivalent.

Engineered sequestration

Approaches that rely on chemistry to capture and store atmospheric greenhouse gases or that capture carbon from the point of origin and durably store them.


The presence of people; livelihoods; environmental services and resources; infrastructure; or economic, social, or cultural assets in places that could be adversely affected.

External forcing

External forcing refers to a forcing agent outside the climate system causing a change in the climate system. Volcanic eruptions, solar variations, and anthropogenic changes in the composition of the atmosphere and land use change are external forcings


Ensuring reliability of electricity supply by supplementing variable renewable energy with dispatchable generation sources such as energy storage.

Fugitive emissions

Intentional or unintentional release of greenhouse gasses that occur during the extraction, processing and delivery of fossil fuels to the point of final use

Greenhouse and Energy Minimum Standards Act(Opens in a new tab/window) (GEMS) Act

Legislation establishing a national framework for appliance and equipment energy efficiency in Australia. It aims to promote the development and adoption of appliances and equipment that use less energy and produce less greenhouse gases.

Geological sequestration

The process of storing carbon dioxide (generally as a supercritical fluid) in suitable geological formations, typically around 2000 metres below the surface. Formations can be onshore or offshore and include depleted oil and gas fields and saline aquifers.

Global surface temperature

The global surface temperature is an estimate of the global mean surface air temperature. However, for changes over time, only anomalies, as departures from a climatology, are used, most commonly based on the area-weighted global average of the sea surface temperature anomaly and land surface air temperature anomaly.

Global warming potential

Global-warming potential or ‘GWP’ is a term used to describe the relative potency, molecule for molecule, of a greenhouse gas in intercepting infrared energy, taking account of how long it remains active in the atmosphere as well as its energy-intercepting properties. The global-warming potentials (GWPs) currently used are those calculated over 100 years. Carbon dioxide is taken as the gas of reference and given a 100-year GWP of 1.

Greenhouse effect

Greenhouse gases effectively absorb thermal infrared radiation, emitted by the Earth’s surface, by the atmosphere itself due to the same gases, and by clouds. Atmospheric radiation is emitted to all sides, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system. This is called the greenhouse effect. Thermal infrared radiation in the troposphere is strongly coupled to the temperature of the atmosphere at the altitude at which it is emitted. In the troposphere, the temperature generally decreases with height. Effectively, infrared radiation emitted to space originates from an altitude with a temperature of, on average, -19°C, in balance with the net incoming solar radiation, whereas the Earth’s surface is kept at a much higher temperature of, on average, 14°C. An increase in the concentration of greenhouse gases leads to an increased infrared opacity of the atmosphere and therefore to an effective radiation into space from a higher altitude at a lower temperature. This causes a radiative forcing that leads to an enhancement of the greenhouse effect, the so-called enhanced greenhouse effect.

Greenhouse gas

Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, which absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. This property causes the greenhouse effect. Water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ozone (O3) are the primary greenhouse gases in the Earth’s atmosphere. Moreover, there are a number of entirely human-made greenhouse gases in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, dealt with under the Montreal Protocol. Besides CO2, N2O, and CH4, the Kyoto Protocol deals with the greenhouse gases sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).

Hard-to-abate emissions

Emissions from essential processes and products with no near-term decarbonisation options.


The potential occurrence of a natural or human-induced physical event that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, and environmental resources.

Indigenous estate

Land that has been purchased, vested, reserved for or leased on behalf of an Aboriginal land trust. Generally freehold but may be leased or reserved on behalf of an Aboriginal land trust. Ownership rights and privileges under Indigenous freehold vary with jurisdiction legislation.


Refers to undertaking emissions reduction projects or activities within an entity’s own value chain or operations. It contrasts with offsetting. When insetting, carbon credits or other verified estimates of abatement generated are used to compensate for emissions from the entity’s activities. One of the incentives for insetting is the ability to demonstrate a carbon neutral or low carbon supply chain.

Industrial Processes and Product use emissions

Industrial Processes and Product Use (IPPU), covers greenhouse gas emissions occurring from industrial processes, from the use of greenhouse gases in products, and from non-energy uses of fossil fuel carbon.

Integrity Committee

The independent statutory committee established under the Carbon Credits (Carbon Farming Initiative) Act 2011 to assess the compliance of methods against the Offsets Integrity Standards.

Currently known as the Emissions Reduction Assurance Committee (ERAC). The Government has announced its intent to re-establish the ERAC as the Carbon Abatement Integrity Committee (CAIC).

Just Transition

The process and the outcome in which burdens and benefits are shared equitably as Australia accelerates emissions reductions, adopts new ways of doing things, and continues to prosper as the world transitions to net zero emissions.

Kyoto Protocol

An international agreement adopted under the United Nations Framework Convention on Climate Change in 1997. It includes binding national targets for developed countries and flexible mechanisms including the Clean Development Mechanism (CDM).

Land surface air temperature

The air temperature as measured in well-ventilated screens over land at 1.5 to 2 m above the ground.

Land use and land use change

Land use refers to the total of arrangements, activities, and inputs undertaken in a certain land cover type (a set of human actions). The term land use is also used in the sense of the social and economic purposes for which land is managed (e.g., grazing, timber extraction, and conservation). Land use change refers to a change in the use or management of land by humans, which may lead to a change in land cover. Land cover and land use change may have an impact on the surface albedo, evapotranspiration, sources and sinks of greenhouse gases, or other properties of the climate system and may thus have radiative forcing and/or other impacts on climate, locally or globally


A probabilistic estimate of the occurrence of a single event or of an outcome, for example, a climate parameter, observed trend, or projected change lying in a given range. Likelihood may be based on statistical or modeling analyses, elicitation of expert views, or other quantitative analyses.

Measurement, reporting and verification (MRV)

MRV frameworks provide systematic approaches for measuring or estimating emissions, reporting these emissions, and verifying these emissions, typically through an independent third-party.

Mitigation (of climate change)

A human intervention to reduce the sources or enhance the sinks of greenhouse gases.

Mitigation (of disaster risk and disaster)

The lessening of the potential adverse impacts of physical hazards (including those that are human-induced) through actions that reduce hazard, exposure, and vulnerability.

National Climate Resilience and Adaptation Strategy

A national strategy released in October 2021 which sets out what the Australian Government will do over the next five years to support efforts across all levels of government, business and the community to better anticipate, manage and adapt to the impacts of climate change.

National Greenhouse and Energy Reporting Scheme

Introduced in 2007, the scheme provides a single national framework for corporations to report on greenhouse gas emissions, energy use and energy production. Corporations that meet a National Greenhouse and Energy Reporting threshold must register and then report each year.

Nationally Determined Contribution

A submission by a Party to the Paris Agreement that articulates the Party’s efforts to contribute to the global task of decarbonisation and adapt to the impacts of climate change.

Nature based Solutions

Actions to protect, conserve, restore, sustainably use and manage natural or modified terrestrial, freshwater, coastal and marine ecosystems which address social, economic and environmental challenges effectively and adaptively, while simultaneously providing human well-being, ecosystem services, resilience and biodiversity benefits.

Net negative emissions

When metric-weighted anthropogenic carbon removals exceed metric-weighted anthropogenic greenhouse gas emissions.

Net zero emissions

An overall balance between greenhouse gas emissions and removals


A process is called nonlinear when there is no simple proportional relation between cause and effect. The climate system contains many such nonlinear processes, resulting in a system with a potentially very complex behavior. Such complexity may lead to abrupt climate change.

Ocean warming

Increases in the temperature of oceans as they absorb increasing amounts of solar radiation due to the greenhouse gas effect

Paris Agreement

An international agreement adopted under the United Nations Framework Convention on Climate Change in 2015. Under the Paris Agreement, the global temperature goal is to keep warming to ‘well below’ 2 degrees Celsius compared with pre-industrial levels, and to ‘pursue efforts to limit the temperature rise to 1.5 degrees Celsius’.


A percentile is a value on a scale of 100 that indicates the percentage of the data set values that is equal to or below it. The percentile is often used to estimate the extremes of a distribution. For example, the 90th (10th) percentile may be used to refer to the threshold for the upper (lower) extremes.


Ground (soil or rock and included ice and organic material) that remains at or below 0°C for at least 2 consecutive years.

Permanence obligations

The legislated requirements to maintain and restore the carbon stored in projects participating under carbon crediting schemes.

Point target

A level of emissions reduction, e.g. -43 per cent to be achieved in a designated target year, e.g. 2030, as compared to emissions in a base year, e.g. 2005.

Ocean acidification

The lowering of the pH of seawater as a result of the chemical processes of carbon dioxide dissolving in oceans.


The extent to which future states of a system may be predicted based on knowledge of current and past states of the system.

Probability density function (PDF)

A probability density function is a function that indicates the relative chances of occurrence of different outcomes of a variable. The function integrates to unity over the domain for which it is defined and has the property that the integral over a sub-domain equals the probability that the outcome of the variable lies within that sub-domain. For example, the probability that a temperature anomaly defined in a particular way is greater than zero is obtained from its PDF by integrating the PDF over all possible temperature anomalies greater than zero. Probability density functions that describe two or more variables simultaneously are similarly defined.


A projection is a potential future evolution of a quantity or set of quantities, often computed with the aid of a model. Projections are distinguished from predictions in order to emphasise that projections involve assumptions concerning, for example, future socioeconomic and technological developments that may or may not be realised, and are therefore subject to substantial uncertainty.

Proxy climate indicator

A proxy climate indicator is a local record that is interpreted, using physical and biophysical principles, to represent some combination of climate-related variations back in time. Climate-related data derived in this way are referred to as proxy data. Examples of proxies include pollen analysis, tree ring records, characteristics of corals, and various data derived from ice cores. The term ‘proxy’ can also be used to refer to indirect estimates of present-day conditions, for example, in the absence of observations

Radiative forcing

Radiative forcing is the change in the net, downward minus upward, irradiance (expressed in W m–2) at the tropopause due to a change in an external driver of climate change, such as, for example, a change in the concentration of carbon dioxide or the output of the Sun. Radiative forcing is computed with all tropospheric properties held fixed at their unperturbed values, and after allowing for stratospheric temperatures, if perturbed, to readjust to radiative-dynamical equilibrium. Radiative forcing is called instantaneous if no change in stratospheric temperature is accounted for. For the purposes of this report, radiative forcing is further defined as the change relative to the year 1750 and, unless otherwise noted, refers to a global and annual average value. Radiative forcing is not to be confused with cloud radiative forcing, a similar terminology for describing an unrelated measure of the impact of clouds on the irradiance at the top of the atmosphere.

Remuneration Tribunal

An independent statutory authority established under the Remuneration Tribunal Act 1973 that sets the remuneration for key Commonwealth offices.


The ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event in a timely and efficient manner, including through ensuring the preservation, restoration, or improvement of its essential basic structures and functions.

Return period

An estimate of the average time interval between occurrences of an event (e.g., flood or extreme rainfall) of (or below/above) a defined size or intensity.

Reversal event

When carbon that was removed from the atmosphere is subsequently released back into the atmosphere, whether by natural disturbance or some other cause.

Risk transfer

The process of formally or informally shifting the financial consequences of particular risks from one party to another whereby a household, community, enterprise, or state authority will obtain resources from the other party after a disaster occurs, in exchange for ongoing or compensatory social or financial benefits provided to that other party.


That part of precipitation that does not evaporate and is not transpired, but flows through the ground or over the ground surface and returns to bodies of water.

Safeguard facility

An industrial facility covered by the Safeguard Mechanism with direct scope 1 emissions of more than 100,000 tonnes of carbon dioxide equivalent per year.

Safeguard Mechanism

A framework for reducing emissions at Australia’s largest industrial facilities. It sets legislated limits—known as baselines—on the greenhouse gas emissions of these facilities. These baselines will decline on a trajectory consistent with achieving Australia’s emission reduction targets.


A plausible and often simplified description of how the future may develop based on a coherent and internally consistent set of assumptions about driving forces and key relationships. Scenarios may be derived from projections, but are often based on additional information from other sources, sometimes combined with a narrative storyline.


Science-based climate-related targets are those that are theoretically feasible, quantifiable such that progress is measurable, and are supported by clear, analytical rationale for why they were set at a given level. The best-known examples are the Paris Agreement goals of limiting global warming to 2 degrees Celsius while pursuing efforts to limit it further to 1.5 degrees Celsius.

Scope 1 Emissions

The release of greenhouse gases into the atmosphere as a direct result of activities occurring within a responsible entity’s control (or geographic boundary).

Scope 2 Emissions

The release of greenhouse gases into the atmosphere from the consumption of electricity, heating, cooling or steam that is generated outside of a responsible entity’s control (or geographic boundary).

Scope 3 Emissions

Greenhouse gases emitted as a consequence of a responsible entity’s activities (other than Scope 2 emissions) but beyond the responsible entity’s control or geographic boundary.

Sea surface temperature (SST)

The sea surface temperature is the temperature of the subsurface bulk temperature in the top few meters of the ocean, measured by ships, buoys, and drifters. From ships, measurements of water samples in buckets were mostly switched in the 1940s to samples from engine intake water. Satellite measurements of skin temperature (uppermost layer; a fraction of a millimeter thick) in the infrared or the top centimeter or so in the microwave are also used, but must be adjusted to be compatible with the bulk temperature.


See biological sequestration, carbon sequestration, engineered sequestration or geological sequestration

Social licence

Gaining landholder and broader community support for new infrastructure projects.

Stationary Energy

The burning of fuels for energy used directly, in the form of heat, steam or pressure.

Storm surge

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


The principle that decisions of government (other things being equal) are best made and implemented, if possible, at the lowest most decentralised level closest to the citizen. Subsidiarity is designed to strengthen accountability and reduce the dangers of making decisions in places remote from their point of application. The principle does not necessarily limit or constrain the action of higher orders of government, it merely counsels against the unnecessary assumption of responsibilities at a higher level.

Sustainable development

Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Synthetic greenhouse gases

Synthetic greenhouse gases are artificial chemicals commonly used in refrigeration and air conditioning, fire extinguishing, foam production and in medical aerosols. Synthetic greenhouse gases generally have high global warming potential; when they are released, they trap heat in the atmosphere.


The altering of fundamental attributes of a system (including value systems; regulatory, legislative, or bureaucratic regimes; financial institutions; and technological or biological systems).


The evaporation of water vapor from the surfaces of leaves through stomata.


An expression of the degree to which a value or relationship is unknown. Uncertainty can result from lack of information or from disagreement about what is known or even knowable. Uncertainty may originate from many sources, such as quantifiable errors in the data, ambiguously defined concepts or terminology, or uncertain projections of human behavior. Uncertainty can therefore be represented by quantitative measures, for example, a range of values calculated by various models, or by qualitative statements, for example, reflecting the judgment of a team of experts.

United Nations Framework Convention on Climate Change (UNFCCC)

The international treaty that works to stabilise greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

The Convention entered into force on 21 March 1994 and has near universal membership.

Urban heat island

The relative warmth of a city compared with surrounding rural areas, associated with changes in runoff, the concrete jungle effects on heat retention, changes in surface albedo, changes in pollution and aerosols, and so on.

Venting and flaring

The disposal of gas that cannot be contained or otherwise handled. Venting activities release methane because the vented gas typically has a high methane content. If the excess gas is burned in flares the emissions of methane will depend on how efficient the burning processes are.


The propensity or predisposition to be adversely affected.


Meeting various human needs, some of which are essential, and includes the ability to pursue one’s goals, to thrive and feel satisfied with their life

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