Glossary P-Q

Glossary of acronyms and specialised terms on the IPCC-DDC website.
The definitions shown here are from the IPCC Fifth Assessment Report (AR5) working group glossaries: WGI, WGII and WGIII. The source working group is indicated on each definition.

A | B | C | D | E | F-G | H-I | J-K | L-M | N-O | P-Q | R | S | T | U-V | W-Z

Particulate matter (PM)

Very small solid particles emitted during the combustion of biomass and fossil fuels. PM may consist of a wide variety of substances. Of greatest concern for health are particulates of diameter less than or equal to 10 nanometers, usually designated as PM10. See also Aerosol. WGIII

PCMDI

Program for Climate Model Diagnosis and Intercomparison

PDF

Portable Document Format

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. WGI

Phenology

The relationship between biological phenomena that recur periodically (e.g., development stages, migration) and climate and seasonal changes. WGII

Photochemical smog

A mix of oxidizing air pollutants produced by the reaction of sunlight with primary air pollutants, especially hydrocarbons. See also Volatile Organic Compounds (VOCs). WG II

Policies (for mitigation of or adaptation to climate change)

Policies are a course of action taken and/or mandated by a government, e.g., to enhance mitigation and adaptation. Examples of policies amied at mitigation are support mechanisms for renewable energy supplies, carbon or energy taxes, and fuel efficiency standards for automobiles. See also Measures. WGIII

Pre-Industrial

See Industrial Revolution

PROVIA

Programme of Research on Climate Change Vulnerability, Impacts and Adaptation