Glossary P-Z
Paludification The process of transforming land into a wetland such as a marsh, a swamp or a bog.
Particulates Very small solid exhaust particles emitted during the combustion of fossil and biomass fuels. Particulates may consist of a wide variety of substances. Of greatest concern for health are particulates of less than or equal to 10 nm in diameter, usually designated as PM10.
Peat Peat is formed from dead plants, typically Sphagnum mosses, which are only partially decomposed due to the permanent submergence in water and the presence of conserving substances such as humic acids.
Peatland Typically a wetland such as a mire slowly accumulating peat.
Pelagic community The community of organisms living in the open waters of a river, a lake or an ocean (in contrast to benthic communities living on or near the bottom of a water body).
Permafrost Perennially frozen ground that occurs where the temperature remains below 0°C for several years.
Phenology The study of natural phenomena that recur periodically (e.g., development stages, migration) and their relation to climate and seasonal changes.
Photochemical smog A mix of photochemical oxidant air pollutants produced by the reaction of sunlight with primary air pollutants, especially hydrocarbons.
Photosynthesis The synthesis by plants, algae and some bacteria of sugar from sunlight, carbon dioxide and water, with oxygen as the waste product. See also carbon dioxide fertilisation, C3 plants and C4 plants.
Physiographic Of, relating to, or employing a description of nature or natural phenomena.
Phytoplankton The plant forms of plankton. Phytoplankton are the dominant plants in the sea, and are the basis of the entire marine food web. These single-celled organisms are the principal agents of photosynthetic carbon fixation in the ocean. See also zooplankton.
Plankton Microscopic aquatic organisms that drift or swim weakly. See also phytoplankton and zooplankton.
Plant functional type (PFT) An idealised vegetation class typically used in dynamic global vegetation models (DGVM).
Polynya Areas of permanently unfrozen sea water resulting from warmer local water currents in otherwise sea-ice covered oceans. They are biological hotspots, since they serve as breathing holes or refuges for marine mammals such as whales and seals, and fish-hunting birds.
Population system An ecological system (not ecosystem) determined by the dynamics of a particular vagile species that typically cuts across several ecological communities and even entire biomes. An example is migratory birds that seasonally inhabit forests as well as grasslands and visit wetlands on their migratory routes.
Potential production Estimated crop productivity under non-limiting soil, nutrient and water conditions.
Pre-industrial See industrial revolution.
Primary production All forms of production accomplished by plants, also called primary producers. See GPP, NPP, NEP and NBP.
Projection The potential evolution of a quality 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 socio-economic and technological developments, that may or may not be realised – and are therefore subject to substantial uncertainty. See also climate projection and climate prediction.
Pteropods Planktonic, small marine snails with swimming organs resembling wings.
Pure rate of time preference The degree to which consumption now is preferred to consumption one year later, with prices and incomes held constant, which is one component of the discount rate.
Radiative forcing Radiative forcing is the change in the net vertical irradiance (expressed in Watts per square metre; Wm–2) at the tropopause due to an internal or external change in the forcing of the climate system, such as a change in the concentration of CO2 or the output of the Sun.
Rangeland Unmanaged grasslands, shrublands, savannas and tundra.
Recalcitrant Recalcitrant organic material or recalcitrant carbon stocks resist decomposition.
Reference scenario Seebaseline/reference.
Reforestation Planting of forests on lands that have previously contained forests but that have been converted to some other use. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000).
Reid’s paradox This refers to the apparent contradiction between inferences of high plant migration rates as suggested in the palaeo-record (particularly after the last Ice Age), and the low potential rates of migration that can be inferred through studying the seed dispersal of the plants involved, e.g., in wind-tunnel experiments.
Reinsurance The transfer of a portion of primary insurance risks to a secondary tier of insurers (reinsurers); essentially ‘insurance for insurers’.
Relative sea-level rise See sea-level rise.
Reservoir A component of the climate system, other than the atmosphere, that has the capacity to store, accumulate or release a substance of concern (e.g., carbon or a greenhouse gas). Oceans, soils, and forests are examples of carbon reservoirs. The term also means an artificial or natural storage place for water, such as a lake, pond or aquifer, from which the water may be withdrawn for such purposes as irrigation or water supply.
Resilience The ability of a social or ecological system to absorb disturbances while retaining the same basic structure and ways of functioning, the capacity for self-organisation, and the capacity to adapt to stress and change.
Respiration The process whereby living organisms convert organic matter to carbon dioxide, releasing energy and consuming oxygen.
Riparian Relating to or living or located on the bank of a natural watercourse (such as a river) or sometimes of a lake or a tidewater.
River discharge Water flow within a river channel, for example expressed in m3/s. A synonym for streamflow.
Runoff That part of precipitation that does not evaporate and is not transpired.
Salinisation The accumulation of salts in soils.
Salt-water intrusion / encroachment Displacement of fresh surface water or groundwater by the advance of salt water due to its greater density. This usually occurs in coastal and estuarine areas due to reducing land-based influence (e.g., either from reduced runoff and associated groundwater recharge, or from excessive water withdrawals from aquifers) or increasing marine influence (e.g., relative sea-level rise).
Savanna Tropical or sub-tropical grassland or woodland biomes with scattered shrubs, individual trees or a very open canopy of trees, all characterised by a dry (arid, semi-arid or semi-humid) climate.
Scenario 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’. See also climate (change) scenario, emissions scenario and SRES.
Sea-ice biome The biome formed by all marine organisms living within or on the floating sea ice (frozen sea water) of the polar oceans.)
Sea-level rise An increase in the mean level of the ocean. Eustatic sea-level rise is a change in global average sea level brought about by an increase in the volume of the world ocean. Relative sea-level rise occurs where there is a local increase in the level of the ocean relative to the land, which might be due to ocean rise and/or land level subsidence. In areas subject to rapid land-level uplift, relative sea level can fall.
Sea wall A human-made wall or embankment along a shore to prevent wave erosion.
Semi-arid regions Regions of moderately low rainfall, which are not highly productive and are usually classified as rangelands. ‘Moderately low’ is widely accepted as between 100 and 250 mm precipitation per year. See also arid region.
Sensitivity Sensitivity is the degree to which a system is affected, either adversely or beneficially, by climate variability or change. The effect may be direct (e.g., a change in crop yield in response to a change in the mean, range or variability of temperature) or indirect (e.g., damages caused by an increase in the frequency of coastal flooding due to sea-level rise).
Sequestration See carbon sequestration.
Silviculture Cultivation, development and care of forests.
Sink Any process, activity, or mechanism that removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.
Snow water equivalent The equivalent volume/mass of water that would be produced if a particular body of snow or ice was melted.
Snowpack A seasonal accumulation of slow-melting snow.
Social cost of carbon The value of the climate change impacts from 1 tonne of carbon emitted today as CO2, aggregated over time and discounted back to the present day; sometimes also expressed as value per tonne of carbon dioxide.
Socio-economic scenarios Scenarios concerning future conditions in terms of population, Gross Domestic Product and other socio-economic factors relevant to understanding the implications of climate change.
See SRES (source: Chapter 6).
SRES The storylines and associated population, GDP and emissions scenarios associated with the Special Report on Emissions Scenarios (SRES) (Nakićenović et al., 2000), and the resulting climate change and sea-level rise scenarios. Four families of socio-economic scenario (A1, A2, B1 and B2) represent different world futures in two distinct dimensions: a focus on economic versus environmental concerns, and global versus regional development patterns.
Stakeholder A person or an organisation that has a legitimate interest in a project or entity, or would be affected by a particular action or policy.
Stock See reservoir.
Stratosphere Highly stratified region of atmosphere above the troposphere extending from about 10 km (ranging from 9 km in high latitudes to 16 km in the tropics) to about 50 km.
Streamflow Water flow within a river channel, for example, expressed in m3/s. A synonym for river discharge.
Sub-alpine The biogeographic zone below the tree line and above the montane zone that is characterised by the presence of coniferous forest and trees.
Succulent Succulent plants, e.g., cactuses, possessing organs that store water, thus facilitating survival during drought conditions.
Surface runoff The water that travels over the land surface to the nearest surface stream; runoff of a drainage basin that has not passed beneath the surface since precipitation.
Sustainable development Development that meets the cultural, social, political and economic needs of the present generation without compromising the ability of future generations to meet their own needs.
Taiga The northernmost belt of boreal forest adjacent to the Arctic tundra.
Thermal expansion In connection with sea-level rise, this refers to 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 an increase in sea level.
Thermocline The region in the world’s ocean, typically at a depth of 1 km, where temperature decreases rapidly with depth and which marks the boundary between the surface and the ocean.
Thermohaline circulation (THC) Large-scale, density-driven circulation in the ocean, caused by differences in temperature and salinity. In the North Atlantic, the thermohaline circulation consists of warm surface water flowing northward and cold deepwater flowing southward, resulting in a net poleward transport of heat. The surface water sinks in highly restricted regions located in high latitudes. Also called meridional overturning circulation (MOC).
Thermokarst A ragged landscape full of shallow pits, hummocks and depressions often filled with water (ponds), which results from thawing of ground ice or permafrost. Thermokarst processes are the processes driven by warming that lead to the formation of thermokarst.
Threshold The level of magnitude of a system process at which sudden or rapid change occurs. A point or level at which new properties emerge in an ecological, economic or other system, invalidating predictions based on mathematical relationships that apply at lower levels.
Transpiration The evaporation of water vapour from the surfaces of leaves through stomata.
Tree line The upper limit of tree growth in mountains or high latitudes. It is more elevated or more poleward than the forest line.
Trophic level The position that an organism occupies in a food chain.
Trophic relationship The ecological relationship which results when one species feeds on another.
Troposphere The lowest part of the atmosphere from the surface to about 10 km in altitude in mid-latitudes (ranging from 9 km in high latitudes to 16 km in the tropics on average) where clouds and ‘weather’ phenomena occur. In the troposphere, temperatures generally decrease with height.
Tsunami A large wave produced by a submarine earthquake, landslide or volcanic eruption.
Tundra A treeless, level, or gently undulating plain characteristic of the Arctic and sub-Arctic regions characterised by low temperatures and short growing seasons.
Uncertainty An expression of the degree to which a value (e.g., the future state of the climate system) is unknown. Uncertainty can result from lack of information or from disagreement about what is known or even knowable. It may have many types of sources, from quantifiable errors in the data to ambiguously defined concepts or terminology, or uncertain projections of human behaviour. Uncertainty can therefore be represented by quantitative measures (e.g., a range of values calculated by various models) or by qualitative statements (e.g., reflecting the judgement of a team of experts). See also confidence and likelihood.
Undernutrition The temporary or chronic state resulting from intake of lower than recommended daily dietary energy and/or protein requirements, through either insufficient food intake, poor absorption, and/or poor biological use of nutrients consumed.
Ungulate A hoofed, typically herbivorous, quadruped mammal (including ruminants, swine, camel, hippopotamus, horse, rhinoceros and elephant).
United Nations Framework Convention on Climate Change (UNFCCC) The Convention was adopted on 9 May 1992, in New York, and signed at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries and the European Community. Its ultimate objective is the ‘stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system’. It contains commitments for all Parties. Under the Convention, Parties included in Annex I aim to return greenhouse gas emissions not controlled by the Montreal Protocol to 1990 levels by the year 2000. The Convention entered in force in March 1994. See also Kyoto Protocol.
Upwelling region A region of an ocean where cold, typically nutrient-rich watersfrom the bottom of the ocean surface.
Urbanisation The conversion of land from a natural state or managed natural state (such as agriculture) to cities; a process driven by net rural-to-urban migration through which an increasing percentage of the population in any nation or region come to live in settlements that are defined as ‘urban centres’.
Vagile Able to migrate.
Vascular plants Higher plants with vascular, i.e., sap-transporting, tissues.
Vector A blood-sucking organism, such as an insect, that transmits a pathogen from one host to another. See also vector-borne diseases.
Vector-borne diseases Disease that are transmitted between hosts by a vector organism (such as a mosquito or tick); e.g., malaria, dengue fever and leishmaniasis.
Vernalisation The biological requirements of certain crops, such as winter cereals, which need periods of extreme cold temperatures before emergence and/or during early vegetative stages, in order to flower and produce seeds. By extension, the act or process of hastening the flowering and fruiting of plants by treating seeds, bulbs or seedlings with cold temperatures, so as to induce a shortening of the vegetative period.
Vulnerability Vulnerability is the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity.
Water consumption Amount of extracted water irretrievably lost during its use (by evaporation and goods production). Water consumption is equal to water withdrawal minus return flow.
Water productivity The ratio of crop seed produced per unit water applied. In the case of irrigation, see irrigation water-use efficiency. For rainfed crops, water productivity is typically 1 t/100 mm.
Water stress A country is water-stressed if the available freshwater supply relative to water withdrawals acts as an important constraint on development. Withdrawals exceeding 20% of renewable water supply have been used as an indicator of water stress. A crop is water-stressed if soil-available water, and thus actual evapotranspiration, is less than potential evapotranspiration demands.
Water-use efficiency Carbon gain in photosynthesis per unit water lost in evapotranspiration. It can be expressed on a short-term basis as the ratio of photosynthetic carbon gain per unit transpirational water loss, or on a seasonal basis as the ratio of net primary production or agricultural yield to the amount of available water.
Welfare An economic term used to describe the state of well-being of humans on an individual or collective basis. The constituents of well-being are commonly considered to include materials to satisfy basic needs, freedom and choice, health, good social relations, and security.
Wetland A transitional, regularly waterlogged area of poorly drained soils, often between an aquatic and a terrestrial ecosystem, fed from rain, surface water or groundwater. Wetlands are characterised by a prevalence of vegetation adapted for life in saturated soil conditions.
Yedoma Ancient organic material trapped in permafrost that is hardly decomposed.
Zoonoses Diseases and infections which are naturally transmitted between vertebrate animals and people.
Zooplankton The animal forms of plankton. They consume phytoplankton or other zooplankton.