Definitions - a

Abrupt Climate Change

A shift in climate (e.g., temperature or precipitation) that occurs faster than the rate of change in the mechanism causing the change.

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Absorption Lines

Any portion of the electromagnetic spectrum (including visible light) that is trapped by free atoms or molecules in the path of the radiation,so  reducing their transmission. In the climate context, this is important for the greenhouse effect since water vapor, carbon dioxide and methane absorb certain wavelengths of infrared radiation.

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Acid Fallout

Molecules of acid formed from reactions high in the atmosphere involving nitrogen, sulfur oxides, and water vapor that settle out of the atmosphere without any additional water.

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Acid Free

Acid Free is used to describe paper which is free from traces of acid; e.g. made under neutral sizing conditions. This helps improve its longevity.

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Acid Rain

Rainwater that has an acidity content greater than the postulated natural pH of about 5.6. It is formed when sulfur dioxides and nitrogen oxides, as gases or fine particles in the atmosphere, combine with water vapor and precipitate as sulfuric acid or nitric acid in rain, snow, or fog. The dry forms are acidic gases or particulates.

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Activated Coal

This is the most commonly used adsorption medium, produced by heating carbonaceous substances or cellulose bases in the absence of air. It has a very porous structure and is commonly used to remove organic matter and dissolved gases from water. Its appearance is similar to coal or peat. Available in granular, powder or block form; in powder form it has the highest adsorption capacity.

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Activated Sludge Process

A biological wastewater treatment process in which a mixture of waste water and activated sludge is agitated and aerated. The activated sludge is then separated from the treated wastewater by sedimentation and disposed of or returned to the process as needed.

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Active Ventilation

Active Ventilation is forced air ventilation, this is where a fan is used to move air into a space or room to provide ventilation.

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Adaptive Capacity

The ability of a system (like an ecosystem) to adapt to climate change or other environmental disturbances. This may mean moderating potential damages, taking advantage of opportunities or coping with the consequences.

In discussions on global warming adaptive capacity often refers to a country. In this case it is currently much lower in developing countries, consequential to poverty.

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The horizontal movement of heat energy. A warm breeze through a relatively cool orchard, for instance.

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Aerated Lagoon

A water treatment pond that speeds up biological decomposition of organic waste by stimulating the growth and activity of bacteria, which are responsible for the degradation.

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Tiny organisms living in the atmosphere. Certain small seeds, bacteria, and spores are examples.

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Particulate matter, solid or liquid, larger than a molecule but small enough to remain suspended in the atmosphere.

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A term coined by Australian writer Clive Hamilton to describe a society where the pursuit of material wealth has led to a lower quality of life with more unhappiness, depression and mental illness due to lack of community and the pressure to get rich.

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Planting of new forests on lands that have not been recently forested.

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A business that markets farm products and equipment, including warehousing, seed monopolization, and fertilizer. The corporatization of farming, resulting in a handful of very large non-local companies owning and managing--and in some cases ruining--millions of high-yield acres

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Production of tree crops in a manner similar to agriculture. Also, production of trees along with regular crop

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Air Barrier

A material often installed around the frame of a building to prevent or reduce the infiltration of air into the interior which could be too hot, too cold or too humid for comfort.

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Air Pollution

Air pollution occurs when the air contains gases, dust, fumes or odour in harmful amounts. That is, amounts which could be harmful to the health or comfort of humans and animals or which could cause damage to plants and materials.

The substances that cause air pollution are called pollutants. Pollutants that are pumped into our atmosphere and directly pollute the air are called primary pollutants. Primary pollutant examples include carbon monoxide from car exhausts and sulfur dioxide from the combustion of coal.

Further pollution can arise if primary pollutants in the atmosphere undergo chemical reactions. The resulting compounds are called secondary pollutants. Photochemical smog is an example of this.

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Air Sealing

Air sealing refers to the steps undertaken to prevent uncontrolled inward or outward air leakage via the building envelope.

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Air Stratification

This is the tendency of heated air to rise and to arrange itself in layers with the warmest air at the top. The assumption here is that there are no external wind sources to keep mixing the air and that the air is in an enclosed space.

A term encountered in passive solar design.

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An area characterized by air with common qualities. Compare Watershed.

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The fraction of the total solar radiation incident on a body that is reflected by it. Albedo can be expressed as either a percentage or a fraction of 1.

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The ratio of reflected to incident light; albedo can be expressed as either a percentage or a fraction of 1. Snow covered areas have a high albedo (up to about 0.9 or 90%) due to their white color, while vegetation has a low albedo (generally about 0.1 or 10%) due to the dark color and light absorbed for photosynthesis. Clouds have an intermediate albedo and are the most important contributor to the Earth's albedo. The Earth's aggregate albedo is approximately 0.3.

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Alcohol Fuels

Alcohol can be blended with gasoline for use as transportation fuel. It may be produced from a wide variety of organic feedstock. The common alcohol fuels are methanol and ethanol. Methanol may be produced from coal, natural gas, wood and organic waste. Ethanol is commonly made from agricultural plants, primarily corn, containing sugar.

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A group of highly reactive chemical compounds used in making resins and dyes. Volatile organic compounds (VOCs). One of the better-known members of this group is formaldehyde.

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The metabolic impact of one plant on another, whether beneficial or harmful. Example: eucalyptus tree toxins that inhibit the growth of certain plants.

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Something organic imported into an ecosystem from outside of it (e.g., nutrients brought by streams or blown in on the wind). Contrasts with Autochthonous.

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The Alpaca (Vicugna pacos) is a domesticated species of South American camelid. This is an animal that produces a thick, full coat which makes incredibly warm jackets, sweaters, hats and blankets. Alpaca fiber is stronger, lighter and more resilient than wool. It’s also finer than cashmere and equal to the warmth of Gortex.

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Alternative Energy

Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).

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Alternative Energy

Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).

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Alternative Fuels

Fuels from sources cleaner than coal or petroleum products: ethanol, methanol, natural gas, solar, wind, geothermal, biodiesel from vegetable oil, etc.

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Ambient Temperature

The temperature of the surrounding area.

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A colorless, pungent, gas that is extremely soluble in water and may be used as a refrigerant. It is also a fixed form of nitrogen that is suitable as fertilizer.

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Anaerobic Digestor

A renewable energy technology that generates heat and electricity from waste organic matter.

Anaerobic digestors follow the same principles as landfill gas capture systems, capturing the methane released by decomposing organic waste such as food or slurry and then burning it to create heat and electricity. The resulting residue can also then be used as a fertilizer.

The technology is becoming increasingly popular across the agricultural sector and advocates claim that it is more cost effective than many alternative renewable energy systems.

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Angle Of Attack

The angle of relative air flow to the blade chord.

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Angle Of Incidence

The angle that a ray of sun makes with a line perpendicular to the surface. For example, a surface that directly faces the sun has a solar angle of incidence of zero, but if the surface is parallel to the sun (for example, sunrise striking a horizontal rooftop), the angle of incidence is 90°.

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Angle Of Repose

The steepest angle that slope, rock, or detritus material settles into without toppling.

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Annual Solar Savings

The annual solar savings of a solar building is the energy savings attributable to a solar feature relative to the energy requirements of a non-solar building.

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The deviation of a measurable unit, (e.g., temperature or precipitation) in a given region over a specified period from the long-term average, often the thirty-year mean, for the same region.

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Antagonistic Effect

A biologic response to exposure to multiple substances that is less than would be expected if the known effects of the individual substances were added together.

See ATSDR Glossary of Terms

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A hard coal containing little volatile matter.

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Human made. In the context of greenhouse gases, emissions that are produced as the result of human activities.

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Anthropogenic Global Warming

Often abbreviated to just AGW. This is global warming which has been caused by human activity in addition to natural global warming.

The science around this is difficult to prove, as identifying a clear indicator of the human contribution which is independent of multiple natural causes is very hard to do in reality. The human element to global warming needs to be clearly and precisely measured against a background of natural global warming that has been occurring since the last ice age. 

Given the, until recent (last 20 years), lack of good direct measurement of the climatic system; a lot of dependence has been placed on proxy measurements, which often have high inherent error and many secondary effects that need to be taken into account. 

Temperature measurement is further complicated by the fact that a global temperature is a 'synthetic measurement'; i.e. it cannot be directly observed 'as is' instantaneously globally, it has to be calculated from sparse measurements (both in time and space) of temperature from multiple locations with differing local environmental conditions. Again this incurs additional errors and growing uncertainty.

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spiritual philosophy based on the teachings of Rudolf Steiner (25 February 1861 - 30 March 1925) which postulates the existence of an objective, intellectually comprehensible spiritual world accessible to direct experience through inner development - more specifically through cultivating conscientiously a form of thinking independent of sensory experience. Steiner was the initiator of biodynamic gardening.

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Cultivation of aquatic plants or animals for harvest and utilization by humans. Usually aquaculture refers to fresh water cultivation, while mariculture refers to seawater cultivation

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Rock formations impermeable to groundwater.

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The underground layer of water-soaked sand and rock that acts as a water source for a well; described as artesian (confined) or water table (unconfined).

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A termed coined by Italian architect Paolo Soleri in 1959 to describe the concept of architecture and ecology working as an integral system. Arcology designs are fully 3-dimensional mega-structure cities which can (theoretically) achieve much greater efficiencies, and promote more social interaction than 2-dimensional cities, while using far less land and consuming fewer resources.

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Mechanism by which water is pushed upward by the hydrostatic pressure of a confined aquifer. Overuse of artesian wells lowers the water table and sometimes makes nearby land sink (subsidence).

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Artic Treeline

The northern limit of tree growth; the sinuous boundary between tundra and boreal forest.

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Artificial Trees

"Artificial trees" are a geo-engineering solution that use amine solutions to capture CO2 out of the atmosphere and sequester it underground.

Also known as "air capture" or "carbon scrubbers", the technology is currently in its formative stages but researchers in the US estimate one tree could take as much as 25 times more CO2 out of the atmosphere each year than a normal tree.

A handful of startups are currently looking to bring the technology to market.

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A mineral fiber that can pollute air or water and cause cancer or asbestosis when inhaled. In most countries it is banned or severely restricted in its use in manufacturing and construction.

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A disease associated with inhalation of asbestos fibers. The disease makes breathing progressively more difficult and can be fatal.

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Atmospheric Circulation Model

A mathematical model for quantitatively describing, simulating, and analyzing the structure of the circulation in the atmosphere and the underlying causes. Sometimes referred to as Atmospheric General Circulation Models or AGCMs (See GCMs as well).

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Atmospheric Concentrations

This is usually the quantity of greenhouse gases relative to the global volume of the atmosphere, expressed in parts per million (ppm). Atmospheric concentrations are often cited for carbon dioxide (CO2) alone or for CO2 equivalents, in which case they are adjusted to reflect all greenhouse gases. Rising atmospheric concentrations can occur even with unchanged levels of annual greenhouse gas emissions.

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A coral island consisting of a ring of coral surrounding a central lagoon. Atolls are common in the Indian and Pacific Oceans.

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The phenomenon of the spontaneous initiation of convection in an atmospheric layer in which the lapse rate is equal to or greater than the autoconvective lapse rate.

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Literally, "self eater." Organisms capable of producing their own food. See primary producers . Contrast with heterotroph .

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Availability Factor

The availability factor of a power plant is the amount of time that it is able to produce electricity over a certain period, divided by the amount of the time in the period. Occasions where only partial capacity is available may or may not be deducted. The availability factor should not be confused with capacity factor.

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Available Heat

The amount of heat energy that may be converted into useful energy from a fuel.

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Avoided Cost

The cost a utility would incur to generate the next increment of electric capacity using its own resources; many landfill gas projects' buy back rates are based on avoided costs.

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Axial Alternator

An alternator design where a flat disc carrying magnets on the face (the Armature) rotates near a flat disc carrying coils (the Stator).

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Azimuth Angle

The angle between true south and the point on the horizon directly below the sun.

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