Global Warming Glossary *

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Pacific decadal variability - Coupled decadal-to-inter-decadal variability of the atmospheric circulation and underlying ocean in the Pacific Basin. It is most prominent in the North Pacific, where fluctuations in the strength of the winter Aleutian Low pressure system co-vary with North Pacific sea surface temperatures, and are linked to decadal variations in atmospheric circulation, sea surface temperatures and ocean circulation throughout the whole Pacific Basin. Such fluctuations have the effect of modulating the El Niño-Southern Oscillation cycle. Key measures of Pacific decadal variability are the North Pacific Index (NPI), the Pacific Decadal Oscillation (PDO) index and the Inter-decadal Pacific Oscillation (IPO) index.

Pacific-North American (PNA) pattern - An atmospheric large-scale wave pattern featuring a sequence of tropospheric high- and low-pressure anomalies stretching from the subtropical west Pacific to the east coast of North America.

Paleoclimate - Climate during periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available.

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 nanometers (0.00000039 inch) in diameter, usually designated as PM₁₀.

Parameterization - The representation of physical effects by simplified parameters in a computer model rather than by computing them dynamically. This technique allows climate modelers to replace highly complex climatic processes or processes that occur on too small scales to be fully represented in a GCM by more simple representations.

Passive solar design - Structural design and construction techniques that enable a building to use solar energy for heating, cooling, and lighting by non-mechanical means.

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).

Perfluorocarbons (PFCs) - Among the six heat-trapping gases (greenhouse gases) to be abated under the Kyoto Protocol. These are by-products of aluminum smelting and uranium enrichment. They also replace chlorofluorocarbons in manufacturing semiconductors. The Global Warming Potential of PFCs is 6500-9200.

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

pH - pH is a dimensionless measure of the acidity of water (or any solution) given by its concentration of hydrogen ions (H+). pH is measured on a logarithmic scale where pH = -log10(H+). Thus, a pH decrease of 1 unit corresponds to a 10-fold increase in the concentration of H+, or acidity.

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 process by which plants take carbon dioxide from the air (or bicarbonate in water) to build carbohydrates, releasing oxygen in the process. There are several pathways of photosynthesis with different responses to atmospheric carbon dioxide concentrations. See Carbon dioxide fertilization; C3 plants; 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 - Microorganisms living in the upper layers of aquatic systems. A distinction is made between phytoplankton, which depend on photosynthesis for their energy supply, and zooplankton, which feed on phytoplankton.

Pleistocene - The earlier of two Quaternary epochs, extending from the end of the Pliocene, about 1.8 Ma, until the beginning of the Holocene about 11.6 ka.

Policies - In UNFCCC parlance, policies are taken and/or mandated by a government - often in conjunction with business and industry within its own country, or with other countries - to accelerate mitigation and adaptation measures. Examples of policies are carbon or other energy taxes, fuel efficiency standards for automobiles, etc. Common and co-ordinated or harmonized policies refer to those adopted jointly by parties.

Pollen analysis - A technique of both relative dating and environmental reconstruction, consisting of the identification and counting of pollen types preserved in peat, lake sediments and other deposits. See proxy.

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.

Post-consumer waste - Waste from consumption activities, e.g. packaging materials, paper, glass, rests from fruits and vegetables, etc.

Post-glacial rebound - The vertical movement of the land and sea floor following the reduction of the load of an ice mass, for example, since the Last Glacial Maximum (21 ka). The rebound is an isostatic land movement.

Potential - In the context of climate change, potential is the amount of mitigation or adaptation that could be - but is not yet - realized over time.   ► Market potential indicates the amount of heat-trapping gas (greenhouse gas) mitigation that might be expected to occur under forecast market conditions including policies and measures in place at the time. It is based on private unit costs and discount rates, as they appear in the base year and as they are expected to change in the absence of any additional policies and measures.   ► Economic potential is in most studies used as the amount of heat-trapping gas (greenhouse gas) mitigation that is cost-effective for a given carbon price, based on social cost pricing and discount rates, including energy savings, but without most externalities. Theoretically, it is defined as the potential for cost-effective heat-trapping gas (greenhouse gas) mitigation when non-market social costs and benefits are included with market costs and benefits in assessing the options for particular levels of carbon prices (as affected by mitigation policies) and when using social discount rates instead of private ones. This includes externalities, i.e., non-market costs and benefits such as environmental co-benefits.   ► Technical potential is the amount by which it is possible to reduce heat-trapping gas (greenhouse gas) emissions or improve energy efficiency by implementing a technology or practice that has already been demonstrated. No explicit reference to costs is made but adopting "practical constraints" may take into account implicit economic considerations.   ► Physical potential is the theoretical (thermodynamic) and sometimes, in practice, rather uncertain upper limit to mitigation.

Potential production - Estimated crop productivity under non-limiting soil, nutrient and water conditions.

Precautionary Principle - A provision under Article 3 of the UNFCCC, stipulating that the parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason to postpone such measures, taking into account that policies and measures to deal with climate change should be cost-effective in order to ensure global benefits at the lowest possible cost.

Precipitable water - The total amount of atmospheric water vapor in a vertical column of unit cross-sectional area. It is commonly expressed in terms of the height of the water if completely condensed and collected in a vessel of the same unit cross section.

Precursors - Atmospheric compounds that are not greenhouse gases or aerosols, but that 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 - The period before the industrial revolution.

Present value - The value of a money amount differs when the amount is available at different moments in time (years). To make amounts at differing times comparable and additive, a date is fixed as the "present." Amounts available at different dates in the future are discounted back to a present value, and summed to get the present value of a series of future cash flows. Net present value is the difference between the present value of the revenues (benefits) with the present value of the costs.

Price elasticity of demand - The ratio of the percentage change in the quantity of demand for a good or service to one percentage change in the price of that good or service. When the absolute value of the elasticity is between 0 and 1, demand is called inelastic; when it is greater than one, demand is called elastic.

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 emphasize that projections involve assumptions - concerning, for example, future socio-economic and technological developments, that may or may not be realized - and are therefore subject to substantial uncertainty. See also climate projection.

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 include pollen analysis, tree ring records, characteristics of corals and various data derived from ice cores.

Pteropods - Planktonic, small marine snails with swimming organs resembling wings.

Public sector leadership programs in energy efficiency - Government purchasing and procurement of energy-efficient products and services. Government agencies are responsible for a wide range of energy-consuming facilities and services such as government office buildings, schools, and health care facilities. The government is often a country's largest consumer of energy and largest buyer of energy-using equipment. Indirect beneficial impacts occur when governments act effectively as market leaders. First, government buying power can create or expand demand for energy-efficient products and services. Second, visible government energy-saving actions can serve as an example for others.

Purchasing Power Parity (PPP) - The purchasing power of a currency is expressed using a basket of goods and services that can be bought with a given amount in the home country. International comparison of, e.g., Gross Domestic Products of countries can be based on the purchasing power of currencies rather than on current exchange rates. PPP estimates tend to lower per capita GDPs in industrialized countries and raise per capita GDPs in developing countries.

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.

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