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

BOREHOLE: Any exploratory hole drilled into the Earth or ice to gather geophysical data. Climate researchers often take ice core samples, a type of borehole, to predict atmospheric composition in earlier years.

CARBON CYCLE: All parts (reservoirs) and fluxes of carbon. The cycle is usually thought of as four main reservoirs of carbon interconnected by pathways of exchange.

EMISSIONS FACTOR: A unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity.
Greenhouse Gas: (GHG) Any gas that absorbs infrared radiation in the atmosphere.

INDIRECT EMISSIONS: Indirect emissions from a building, home or business are those emissions of greenhouse gases that occur as a result of the generation of electricity used in that building.

METRIC TON: Common international measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2205 lbs or 1.1 short tons.

MOUNT PINATUBO: A volcano in the Philippine Islands that erupted in 1991. The eruption of Mount Pinatubo ejected enough particulate and sulfate aerosol matter into the atmosphere to block some of the incoming solar radiation from reaching Earth’s atmosphere.

NATURAL GAS: Underground deposits of gases consisting of 50 to 90 percent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).

PARTICULATE MATTER: (PM) Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists or aerosols.

SENSITIVITY: The degree to which a system is affected, either adversely or beneficially, by climate variability or change.

SINK: Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas or aerosol from the atmosphere.
Thermal Expansion: 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, which leads to an increase in sea level.

WASTEWATER: Water that has been used and contains dissolved or suspended waste materials.

Terms and definitions provided here were abstracted from a glossary of terms and definitions published by the U.S. Environmental Protection Agency (