Acid deposition

A phenomenon whereby acidic atmospheric pollutants are deposited on earth.

Acid rain

See acid deposition


A suspension of nanoscopic airborne solid or liquid particles that reside in the atmosphere for at least several hours.

Air capture

The direct capture of CO2 and other GHGs from the atmosphere.


The fraction of solar radiation reflected by a surface or object.

Anthropogenic emissions

Emissions of greenhouse gases (GHGs), precursors of GHGs and aerosols caused by human activities.

Anthropogenic removals

The withdrawal of GHGs from the atmosphere as a result of deliberate human activities.


The gaseous envelope surrounding the Earth.

Black carbon (BC)

Operationally defined aerosol type based on measurement of light absorption and chemical reactivity and/or thermal stability; soot.

Chlorofluorocarbon (CFC)

Any of several organic compounds made up of carbon, hydrogen, fluorine, and chlorine – ozone-depleting gases that are covered under the 1987 Montreal Protocol.

Clean Sky Joint Undertaking (CSJU)

A joint initiative established by the European Commission and the European aviation industry to research and develop technologies that reduce GHG emissions and other forms of pollution in the aviation industry.

Convention on Long-Range Transboundary Air Pollution , 1979 (LRTAP)

A regional framework applicable to Europe, North America and Russia and former East Bloc countries, for reducing transboundary air pollution.


In a climate change context, the point in time when the concentration of GHGs in the earth’s Atmosphere begins to decline on a year-to-year basis.


The amount of energy consumed in direct and indirect transformations to make a product or service.


Pollution discharged into the atmosphere from residential chimneys, smokestacks, other vents and surface areas of commercial or industrial facilities and from motor vehicle, locomotive, or aircraft exhausts.

Emission factor

The relationship between the amount of pollution produced and the amount of raw material processed.

Emission intensity

The rate of pollutant emissions per unit of economic activity.

Emission pathway

See Pathway

Emission Reduction Target

An emission reduction objective that entities aim to reach within a given time frame.

Emission Reduction Unit (ERU)

A Kyoto Protocol unit equal to 1 metric tonne of CO2 equivalent.

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