Terminology

Climate Change Science

Greenhouse Gases (GHG)

Gases that form a thick blanket in the earth's upper atmosphere and absorb radiation emitted by the earth’s surface and by clouds (infrared radiation), trapping part of the absorbed energy which, in turn, warms the planetary surface.

Greenhouse gases are released into the atmosphere as a result of both natural processes and human activity. According to the Intergovernmental Panel on Climate Change (IPCC), the most important greenhouse gases are water vapour, carbon dioxide, nitrous oxide, methane, and ozone. The Kyoto Protocol attributes human-induced (anthropogenic) climate change to increased emission of six greenhouse gases since the Industrial Revolution. The six are: carbon dioxide, methane, nitrous oxide, perfluorocarbons, hydrofluorocarbons, and sulphur hexafluoride. In addition, the amount of water vapour in the atmosphere may be increasing as a consequence of global warming.

Emissions Reduction

Either: the absolute reduction in the level of future human-induced GHG emissions below the level of emissions in a selected period in the past,

Or: a reduction in the level of future GHG emissions below the level of emissions that would result from a continuation of current trends.

Global Warming Potential (GWP)

The radiative efficiency (heat-absorbing capacity) of each greenhouse gas relative to that of carbon dioxide (CO₂), as well as the decay rate of each gas (the amount removed from the atmosphere over a given number of years) relative to that of CO₂.

The GWP provides a construct for converting emissions of various gases into a uniform measure denominated in carbon or carbon dioxide equivalent (CO₂^e).

Carbon Dioxide Equivalent (CO₂e)

The mass of a greenhouse gas (or mixture of gases) that would have the same global warming potential as a given amount of carbon dioxide.

Land Use, Land Use Change and Forestry (LULUCF)

Activities that can mitigate climate change by sequestering carbon and creating carbon sinks.

Sequestration

Natural process whereby carbon dioxide is removed from the atmosphere by new growth vegetation and stored (sequestered) in above- and below-ground biomass and soil biota.

Also referred to as carbon sequestration.

Sinks

Locations that absorb and store carbon dioxide.

Examples include locations characterised by organically rich soils, dense root mass, or new growth forests and trees. Also referred to as carbon sinks.