California Climate Change Glossary

Letter P

Parametrize (Parametrization). In climate modeling, this term refers to the technique of representing processes that cannot be explicitly resolved a the resolution of the model (sub-grid scale processes) by the relationships between the area averaged effect of such sub-gird scale processes and the larger scale flow. (IPCC)

Particulates. Tiny pieces of solid or liquid matter, such as soot, dust, fumes, or mist. (EPA)

Perfluorocarbons (PFCs). A group of human-made chemicals composed of carbon and fluorine only: CF4 and C2F6. These chemicals, specifically CF4 and C2F6, (along with hydrofluorocarbons) were introduced as alternatives to the ozone depleting substances. In addition, they 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 6,300 and C2F6 has a GWP of 12,500. (EPA)

Photosynthesis. The process by which green plants use light to synthesize organic compounds from carbon dioxide and water. In the process oxygen and water are released. Increased levels of carbon dioxide can increase net photosynthesis in some plants. Plants create a very important reservoir for carbon dioxide. (EPA)

Pollutant. Strictly, too much of any substance in the wrong place or at the wrong time is a pollutant. More specifically, atmospheric pollution may be defined as the presence of substances in the atmosphere, resulting from man-made activities or from natural processes that cause adverse effects to human health, property, and the environment. (EPA)

Portfolio Analysis. The mix of actions available to policy makers to reduce emissions or adapt to climate change. (IPCC)

Precautionary Approach. The approach promoted under the Framework Convention of Climate Change to help achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous interference with the climate system. (EPA)

Precession. The tendency of the Earth's axis to wobble in space over a period of 23,000 years. The Earth's precession is one of the factors that results in the planet receiving different amounts of solar energy over extended periods of time. (EPA)

Precursors. Atmospheric compounds that are not greenhouse gases but can enhance greenhouse gas induced processes by contributing to physical or chemical processes regulating greenhouse gas production or destruction rates. (Lenn)

Primary Energy. Energy embodied in natural resources (e.g. coal, crude oil, sunlight, uranium) that has not undergone any anthropogenic conversions or transformations. (IPCC)

Proxy Climate Indicators. 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. (Lenn)