Glossary Terms: All | A-D | E-I | J-Q | R-Z |

Early Crediting: A provision that allows crediting of emission reductions achieved prior to the start of a legally imposed emission control period. These credits can then be used to assist in achieving compliance once a legally imposed system begins.

Ecosystem: A community of organisms and its physical environment.

Eco-Tourism: Responsible travel to natural areas that conserves the environment and improves the well-being of local people.

EER/Energy Efficiency Ratio: The measure of the instantaneous energy efficiency of room air conditioners; the cooling capacity in Btu/hr divided by the watts of power consumed at a specific outdoor temperature (usually 95 degrees Fahrenheit). While the SEER considers yearlong efficiency (kWh), EER is a measure of the maximum use at a given time (kW). (EERE/PATH)

Emissions: The release of substances (e.g., greenhouse gases) into the atmosphere.

Emissions Cap: A mandated restraint in a scheduled timeframe that puts a “ceiling” on the total amount of anthropogenic greenhouse gas emissions that can be released into the atmosphere. This can be measured as gross emissions or as net emissions (emissions minus gases that are sequestered).

Emissions Reduction Unit (ERU): Emissions reductions generated by projects in Annex B countries that can be used by another Annex B country to help meet its commitments under the Kyoto Protocol. Reductions must be additional to those that would otherwise occur.

Emissions Trading: A market mechanism that allows emitters (countries, companies or facilities) to buy emissions from or sell emissions to other emitters. Emissions trading is expected to bring down the costs of meeting emission targets by allowing those who can achieve reductions less expensively to sell excess reductions (e.g. reductions in excess of those required under some regulation) to those for whom achieving reductions is more costly.

Energy: The ability to do work or the ability to move an object. Electrical energy is usually measured in kilowatt hours (kWh), while heat energy is usually measured in British thermal units (Btu).

Energy Conservation: To reduce or manage energy consumption in a cost-effective and energy-efficient manner. (PUC)

Energy Efficiency: Refers to activities that are aimed at reducing the energy used by substituting technically more advanced equipment, typically without affecting the services provided. Examples include high-efficiency appliances, efficient lighting programs, high-efficiency heating, ventilating and air conditioning (HVAC) systems or control modifications, efficient building design, advanced electric motor drive, and heat recovery systems.

Energy-Efficient Mortgages: A type of home mortgage that takes into account the energy savings of a home with cost-effective energy saving improvements that reduce energy costs, thereby providing the homeowner additional money for the mortgage payment. A borrower can qualify for a larger loan amount than otherwise would be possible. (EERE)

Energy Resources: The available supply and price of fossil and alternative resources will play a huge role in estimating how much a greenhouse gas constraint will cost. In the U.S. context, natural gas supply (and thus price) is particularly important, as it is expected to be a transition fuel to a lower carbon economy.

ENERGY STAR: A joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy that establishes voluntary, minimum energy efficiency standards for various products, and allows those products that meet the standards to bear the ENERGY STAR label.

Energy Star Qualified New Homes Program: A program of the U.S. Environmental Protection Agency (EPA) and Dept. of Energy (DOE) to distinguish homes that are more energy efficient (30% > than the norm) as required by code. An Energy Star qualified home means that the home builder has taken extraordinary steps to design and build a structure that will be among the most efficient new homes. The homes are inspected by home energy raters, who verify that the home meets the technical specifications and performance standards established for Energy Star qualification. (

Energy Star Qualified Products: Appliances and other products that meet strict energy efficiency guidelines set by the EPA and DOE. Products in more than 50 categories are eligible for the Energy Star label. They use less energy, save money, and help protect the environment and are identified with the Energy Star label.

ENERGY STAR Rated Programmable Thermostat: A thermostat generally having two different programming schedules (one for weekdays and a second for weekend programming), at least four possible programming events for each programming period (i.e., wake, leave, return, and sleep settings), a setback/setup period of at least eight hours in length, with schedules included in the default program.

Enhanced Greenhouse Effect: The increase in the natural greenhouse effect resulting from increases in atmospheric concentrations of GHGs due to emissions from human activities.

Entry Into Force: The point at which international climate change agreements become binding. The United Nations Framework Convention on Climate Change (UNFCCC) has entered into force. In order for the Kyoto Protocol to do so as well, 55 Parties to the Convention must ratify (approve, accept, or accede to) the Protocol, including Annex I Parties accounting for 55 percent of that group's carbon dioxide emissions in 1990. As of June 2003, 110 countries had ratified the Protocol, representing 43.9 percent of Annex I emissions.

Ethanol: A colorless liquid that burns to produce water and carbon dioxide. The vapor forms an explosive mixture with air and may be used as a fuel in internal combustion engines.

European Community: As a regional economic integration organization, the European Community can be and is a Party to the UNFCCC; however, it does not have a separate vote from its members (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxemburg, the Netherlands, Portugal, Spain, Sweden, and the United Kingdom).

Evapotranspiration: The process by which water re-enters the atmosphere through evaporation from the ground and transpiration by plants.

Flat-Plate Solar Connector: A device designed to capture the sun’s energy and produce low-temperature heat energy. They are commonly used as collectors in solar heating systems.

Forest Carbon Sequestration: The uptake and storage of carbon by forests.

Fossil Fuels: Fuels (coal, oil, natural gas, etc.) that result from the compression of ancient plant and animal life formed over millions of years.

Gas-Condensing Hot Water Heater: Gas-condensing water heaters are is similar to conventional gas, tank hot water heaters with the exception that they are designed to condense the water vapor in the hot flue gas, thereby transferring the heat of condensation to the hot water, improving the efficiency of the heater, but resulting in a slightly acidic water drainage.

Gas to Liquids (GTL): A process that combines the carbon and hydrogen elements in natural gas molecules to make synthetic liquid petroleum products, such as diesel fuel.

General Circulation Model (GCM): A computer model of the basic dynamics and physics of the components of the global climate system (including the atmosphere and oceans) and their interactions which can be used to simulate climate variability and change.

Generating Capacity: The amount of electrical power a power plant can produce.

Generator: A device that turns mechanical energy into electrical energy. The mechanical energy is sometimes provided by an engine or turbine.

Geothermal Energy: The heat or energy that is produced by natural processes inside the earth. It can be taken from hot springs, reservoirs of hot water deep below the ground, or by breaking open the rock itself.

Global Warming: The progressive gradual rise of the Earth's average surface temperature thought to be caused in part by increased concentrations of GHGs in the atmosphere.

Global Warming Potential (GWP): A system of multipliers devised to enable warming effects of different gases to be compared. The cumulative warming effect, over a specified time period, of an emission of a mass unit of CO2 is assigned the value of 1. Effects of emissions of a mass unit of non-CO2 greenhouse gases are estimated as multiples. For example, over the next 100 years, a gram of methane (CH4) in the atmosphere is currently estimated as having 23 times the warming effect as a gram of carbon dioxide; methane's 100-year GWP is thus 23. Estimates of GWP vary depending on the time-scale considered (e.g., 20-, 50-, or 100-year GWP), because the effects of some GHGs are more persistent than others.

Gray Water: Domestic wastewater composed of wash water from kitchen, bathroom, and laundry sinks, tubs, and washers.

Green Building: The practice of increasing the efficiency of buildings and their use of energy, water, and materials and reducing building impacts on human health and the environment through optimal siting, design, construction, operation, maintenance, and waste removal – the complete building life cycle. Energy Efficiency is the key element for green building.

Greenhouse Effect: The insulating effect of atmospheric greenhouse gases (e.g., water vapor, carbon dioxide, methane, etc.) that keeps the Earth's temperature about 60°F warmer than it would be otherwise.

Green Electricity or Green Power: Electricity produced from sustainable sources (wind, solar) by methods that have minimal negative impact on the environment, including energy conservation. (GGGC)

Greenhouse Gas (GHG): Any gas that contributes to the "greenhouse effect."

Green Power Purchasing/ Aggregation Policies: Municipalities, state governments, businesses, and other nonresidential customers can play a critical role in supporting renewable energy technologies by buying electricity from renewable resources. At a local level, green power purchasing can mean buying green power for municipal facilities, streetlights, water pumping stations, and the like. A few states allow local governments to aggregate the electricity loads of the entire community to purchase green power and even to join with other communities to form an even larger green power purchasing block. This is often referred to as “Community Choice.” (DSIRE)

Green Tags (or Renewable Energy Certificates): Green tags are transferable rights for renewable energy. A renewable energy provider is issued one green tag for each 1,000 KWh of energy it produces. The energy is sold into the electrical grid, and the green tag or REC can be sold on the open market for additional profit. The credits are purchased by firms or individuals who either want or are required to generate a portion of their energy from renewable sources. Green Tags (or Renewable Energy Certificates): Green tags are transferable rights for renewable energy. A renewable energy provider is issued one green tag for each 1,000 KWh of energy it produces. The energy is sold into the electrical grid, and the green tag or REC can be sold on the open market for additional profit. The credits are purchased by firms or individuals who either want or are required to generate a portion of their energy from renewable sources. (Wikipedia)

Grid: A network for the transmission of electricity throughout the state, region, or nation. The term is also used to refer to the layout of an electric distribution system.

Ground-Level Ozone: In the troposphere, the air closest to the Earth's surface, ground-level or "bad" ozone is a pollutant that is a significant health risk, especially for children with asthma. It also damages crops, trees and other vegetation. It is a main ingredient of urban smog.

Group of 77 and China, or G77/China: An international organization established in 1964 by 77 developing countries; membership has now increased to 133 countries. The group acts as a major negotiating bloc on some issues including climate change.

Healthy Homes: Homes that are designed, built, or remodeled to create and maintain a healthy indoor environment. Healthy home building is an integral part of whole house and green building practices, with a focus on making the homes dry, clean, well ventilated, free of combustion by-products and toxic chemicals, pest-free, and comfortable.

Heating Oil (Oil): Also commonly known as oil heat or No. 2 heating oil, is a liquid petroleum product used in boilers or furnaces. Heating oil is usually delivered by truck to residential and commercial buildings.

Heat Pump Hot Water Heater: Heat pump water heater technology uses a vapor compression refrigeration system to transfer heat from the surrounding air to water stored in a tank. These compressors in these heaters are typically powered by electricity.

Heavy metals: Metallic elements with high atomic weights; (e.g. mercury, chromium, cadmium, arsenic, and lead); can damage living things at low concentrations and tend to accumulate in the food chain.

HGWP (High Global Warming Potential): Some industrially produced gases such as sulfur hexafluoride (SF6), perfluorocarbons (PFCs), and hydrofluorocarbons (HFCs) have extremely high GWPs. Emissions of these gases have a much greater effect on global warming than an equal emission (by weight) of the naturally occurring gases. Most of these gases have GWPs of 1,300 - 23,900 times that of CO2. These GWPs can be compared to the GWPs of CO2, CH4, and N2O which are presently estimated to be 1, 23 and 296, respectively.

High Efficiency Tank: A natural gas, tank hot water heater with an Energy Factor of at least 0.62. (The Energy Factor is a measure of the heat energy in the hot water relative to the energy input to the water heater; a higher number indicates greater efficiency.)

High-Performing Tank: A natural gas, tank hot water heater with an Energy Factor of at least 0.67. (The Energy Factor is a measure of the heat energy in the hot water relative to the energy input to the water heater; a higher number indicates greater efficiency.)

Home Energy Audit: An assessment of a home or apartment to determine the energy efficiency of the home and its equipment. An audit should include an analysis of the utility bills, interview with the residents, inspection of the heating and cooling equipment, appliances, building structure, and insulation from basement to attic. It may involve the use of diagnostic equipment, such as a blower door, to identify leaks. The audit results in a list of recommended measures to improve the energy efficiency of the home.

Home Energy Rating Systems (HERS): A nationally recognized energy rating program that gives builders, mortgage lenders, secondary lending markets, homeowners, sellers, and buyers a precise evaluation of the energy features in homes. Builders can use this system to gauge the energy quality in their home and also to have a rating on this home on which prospective buyers and lenders can compare to other similarly built homes. (EERE)

Hot Air: A situation in which emissions (of a country, sector, company or facility) are well below a target due to the target being above emissions that materialized under the normal course of events (i.e. without deliberate emission reduction efforts). Hot air can result from over-optimistic projections of growth. Emissions are often projected to grow roughly in proportion to GDP, and GDP is often projected to grow at historic rates. If a recession occurs and fuel use declines, emissions may be well below targets since targets are generally set in relation to emission projections. If emission trading is allowed, an emitter could sell the difference between actual emissions and emission targets. Such emissions are considered hot air because they do not represent reductions from what would have occurred in the normal course of events.

Horsepower: A unit for measuring the rate of work (or power) equivalent to 33,000 foot-pounds per minute, or 746 watts.

House as a System (Whole House System): The approach to home design, building, remodeling, and weatherization that recognizes how all the features in a home are connected and that changing one component can greatly affect another part of the house. It is based on the principles of building science and relies on diagnostics to verify results. Using this approach will improve not only the overall energy efficiency of the home but also its comfort, indoor air quality, safety, durability, and affordability.

Hydroelectric Power Plant: A power plant that uses moving water to power a turbine generator to produce electricity.

Hydrofluorocarbons (HFCs): HFCs are synthetic industrial gases, primarily used in refrigeration and semi-conductor manufacturing as commercial substitutes for chlorofluorocarbons (CFCs). There are no natural sources of HFCs. The atmospheric lifetime of HFCs is decades to centuries , and they have 100-year "global warming potentials" thousands of times that of CO2, depending on the gas. HFCs are among the six greenhouse gases to be curbed under the Kyoto Protocol.

Hydrogen: A colorless, odorless, highly flammable gaseous element. It is the lightest of all gases and the most abundant element in the universe, occurring chiefly in combination with oxygen in water and also in acids, bases, alcohols, petroleum, and other hydrocarbons.

Hydrokinetic and Wave Energy Conversion Devices: Generate electricity from waves or directly from the flow of water in ocean currents, tides, or inland waterways.

Impact: An effect of climate change on the structure or function of a system.

Incandescent Bulb: A light bulb that produces light by passing electrical current through a thin filament, heating the filament and causing it to emit light. Conventional light bulbs with screw bases are incandescent bulbs.

Incentive-Based Regulation: A regulation that uses the economic behavior of firms and households to attain desired environmental goals. Incentive-based programs involve taxes on emissions or tradable emission permits. The primary strength of incentive-based regulation is the flexibility it provides the polluter to find the least costly way to reduce emissions.

Infrared Thermography: The science of using infrared imaging to detect radiant energy or heat loss in a building. The infrared camera or scanner electronically senses heat radiated by objects and converts that thermal energy into images visible to the human eye. Some scanners can automatically record these images on video. Used in conjunction with a blower door during home audits, the scanner can provide valuable data about air leakage sites and thermal bypasses. (WAPTAC)

Integrated Gasification Combined Cycle (IGCC): An alternative process for achieving efficiency improvements in conventional pulverized coal-fired power plants. IGCC plants use a gasifier to convert coal (or other carbon-based materials) to syngas, which drives a combined cycle turbine to produce electricity. (World Coal Institute)

Inter-City Bus: A bus used to travel from one city to another, generally tens to hundreds of miles away, with limited stops.

Inter-City Train: A train used to travel from one city to another, generally tens to hundreds of miles away, with limited stops.

Intergenerational Equity: The fairness of the distribution of the costs and benefits of a policy when costs and benefits are borne by different generations. In the case of a climate change policy the impacts of inaction in the present will be felt in future generations.

Intergovernmental Panel on Climate Change (IPCC): The IPCC was established in 1988 by the World Meteorological Organization and the UN Environment Programme. The IPCC is responsible for providing the scientific and technical foundation for the United Nations Framework Convention on Climate Change (UNFCC); primarily through the publication of periodic assessment reports (see "Second Assessment Report" and "Third Assessment Report").