Climate Change Glossary
Word Definitions Related to
Climate Change and Global Warming
Parabolic
A plane curve formed by the intersection of a right circular cone and a plane parallel to an element of the cone or by the locus of points equidistant from a fixed line and a fixed point not on the line. What’s that? A bowl shaped trough that focuses sunlight into a narrow beam. The bowl reflects the incoming rays of the sun to a receiving element at the centre of the bowl or trough.
Parametrization
In climate models, this term refers to the technique of representing processes, that cannot be explicitly resolved at the spatial or temporal resolution of the model (sub-grid scale processes), by relationships between the area or time averaged effect of such sub-grid scale processes and the larger scale flow.
Particulate Matter (PM)
Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists or aerosols. The physical characteristics of particles, and how they combine with other particles, are part of the feedback mechanisms of the atmosphere. See aerosol, sulfate aerosols.
Parts Per Billion (ppb)
Number of parts of a chemical found in one billion parts of a particular gas, liquid, or solid mixture. See concentration.
Parts Per Million (ppm)
Number of parts of a chemical found in one million parts of a particular gas, liquid, or solid. See concentration.
Patterns of climate variability
Natural variability of the climate system, in particular on seasonal and longer time-scales, predominantly occurs in preferred spatial patterns, through the dynamical non-linear characteristics of the atmospheric circulation and through interactions with the land and ocean surfaces. Such spatial patterns are also called “regimes” or “modes”. Examples are the North Atlantic Oscillation (NAO), the Pacific-North American pattern (PNA), the El Niño-Southern Oscillation (ENSO), and the Antarctic Oscillation (AO).
Perfluorocarbons (PFCs)
A group of human-made chemicals composed of carbon and fluorine only. These chemicals (predominantly CF4 and C2F6) were introduced as alternatives, along with hydrofluorocarbons, to the ozone depleting substances. In addition, PFCs are emitted as by-products of industrial processes and are also used in manufacturing. PFCs do not harm the stratospheric ozone layer, but they are powerful greenhouse gases: CF4 has a global warming potential (GWP) of 5,700 and C2F6 has a GWP of 11,900. The GWP is from the IPCC's Third Assessment Report (TAR). See ozone depleting substance.
Photosynthesis
The process by which plants take CO2 from the air (or bicarbonate in water) to build carbohydrates, releasing O2 in the process. There are several pathways of photosynthesis with different responses to atmospheric CO2 concentrations. See carbon sequestration, carbon dioxide fertilization.
Pool
See: Reservoir.
Post-glacial rebound
The vertical movement of the continents and sea floor following the disappearance and shrinking of ice sheets, e.g. since the Last Glacial Maximum (21 ky BP). The rebound is an isostatic land movement.
Precession
The comparatively slow torquing of the orbital planes of all satellites with respect to the Earth's axis, due to the bulge of the Earth at the equator which distorts the Earth's gravitational field. Precession is manifest by the slow rotation of the line of nodes of the orbit (westward for inclinations less than 90 degrees and eastward for inclinations greater than 90 degrees).
Precipitation
Pre·ci·pi·ta·tion [pri-"si-p&-'tA-sh&n]. Rain, hail, mist, sleet, snow or any other moisture that falls to the Earth.
Precursors
Atmospheric compounds which themselves are not greenhouse gases or aerosols, but which have an effect on greenhouse gas or aerosol concentrations by taking part in physical or chemical processes regulating their production or destruction rates.
Pre-industrial
See: Industrial revolution.
Projection (generic)
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, e.g., future socio-economic and technological developments that may or may not be realised, and are therefore subject to substantial uncertainty. See also Climate projection; Climate prediction.
Proxy
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 are: tree ring records, characteristics of corals, and various data derived from ice cores.
Proxy climate indicator
Variables that are an indirect measure of some combination of climate-related variations back in time. These are used to determine temperature in a time when the thermometer was not yet invented. Examples include tree ring records, characteristics of corals, fraction of melted ice, concentration of salts and acids and the load of pollen trapped in air bubbles.
