Glossary

adaptation
Adjustment or preparation of natural or human systems to a new or changing environment which moderates harm or exploits beneficial opportunities.

anthropogenic
Made by people or resulting ossrom human activities; usually used in the context of emissions that are produced as a result of human activities.

biofuel
Gas or liquid fuel made from plant material.  Includes wood, wood waste, wood liquors, peat, railroad ties, wood sludge, spent sulfite liquors, agricultural waste, straw, tires, fish oils, tall oil, sludge waste, waste alcohol, municipal solid waste, landfill gases, other waste, and ethanol blended into motor gasoline.

biogas
A gaseous mixture composed principally of carbon dioxide and methane  that is generated from the biological decomposition of organic materials in the absence of oxygen. Depending on the type of organic source material and how it is processed, it also contains trace amounts of  hydrocarbons other than methane, hydrogen sulfide, hydrogen, nitrogen, oxygen, carbon monoxide, ammonia, and water. Common feedstocks of biogas include landfills, wastewater treatment plants, food waste, livestock manure and other agricultural residues or biomass.

biomass
Materials that are biological in origin, including organic material (both living and dead) from above and below ground, for example, trees, crops, grasses, tree litter, roots, and animals and animal waste.

biomethane
A form of biogas that has been processed to meet pipeline quality standards by increasing the fraction of methane via the removal of carbon dioxide, hydrogen sulfide, and other trace constituents. Such processing produces a gas that can shipped in gas pipelines and used interchangeably with conventional (fossil or geologic) natural gas. Also called “biogenic” gas..

carbon capture and sequestration (CCS)
A set of technologies that could greatly reduce carbon dioxide emissions from new and existing coal- and gas-fired power plants, industrial processes, and other stationary sources of carbon dioxide. It is a three-step process that includes capture of carbon dioxide from power plants or industrial sources; transport of the captured and compressed carbon dioxide (usually in pipelines); and underground injection and geologic sequestration, or permanent storage, of that carbon dioxide in rock formations that contain tiny openings or pores that trap and hold the carbon dioxide.

carbon dioxide (CO2)
A naturally occurring gas, and also a by-product of burning fossil fuels and biomass, as well as land-use changes and other industrial processes. It is the principal human caused greenhouse gas that affects the Earth’s radiative balance. It is the reference gas against which other greenhouse gases are measured and therefore has a global warming potential (GWP) equal to 1.

carbon dioxide equivalent  (CO2-eq, CO2-e)
A unit of measurement that allows the effect of different greenhouse gases and other factors to be compared using carbon dioxide as a standard unit for reference. CO2-e are commonly expressed as “million metric tons of carbon dioxide equivalents (MMTCO2-e).” The carbon dioxide equivalent for a gas is derived by multiplying the tons of the gas by its associated global warming potential (GWP):

MMTCO2-e = (million metric tons of a gas) * (GWP of the gas)

carbon footprint
The total volume of GHG emissions caused by a community, organization, event,  product, or person.

carbon intensity
The number of emissions of carbon dioxide released per unit of another variable such as Gross Domestic Product (GDP), output energy use or transport

carbon offset
A credit for greenhouse gas reductions achieved by one party that can be purchased and used to compensate (offset) the emissions of another party. Offsets are typically measured in tons of CO2-equivalents, and are bought and sold through a number of international brokers, online retailers, and trading platforms. Common forms are included investments in renewable energy, energy efficiency, and forestry.

carbon sink
A biological system or other natural environment, such as a forest or a body of  water, that absorbs more carbon dioxide from the atmosphere than it releases.

carbon stock
The carbon embodied in a biological system, such as oceans, trees and the  atmosphere. A carbon stock that is taking up carbon is called a “sink” and one that  is releasing carbon is called a “source”.

climate
(i) the average weather; (ii) the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years.  The relevant quantities are most often surface variables such as temperature, precipitation, and wind.

climate change
A change in the state of the climate that can be identified by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer.

co-benefits
The positive effects that a policy or measure aimed at one objective might have on other objectives, irrespective of the net effect on overall social welfare.

co-generation
An energy conversion process in which more than one useful product (e.g.,  electricity and heat or steam) is generated from the same energy input stream.  Also referred to as combined heat and power (CHP).

combined heat and power (CHP)
See co‐generation.

concentration
Amount of a chemical in a particular volume or weight of air, water, soil, or other medium.

decarbonization
(i) The declining average carbon intensity of primary energy production over time; (ii) the reduction of carbon emissions from energy supply chains and industrial processes; (iii) the process by which countries or other entities aim to achieve a low-carbon economy, or by which individuals aim to reduce their consumption of carbon.

direct emissions
Greenhouse gas emissions from sources that are owned or controlled by the reporting entity.

emissions
The release of a substance (usually a gas when referring to the subject of climate change) into the atmosphere.

emission factor
A unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity (e.g., grams of carbon dioxide emitted per gallon of gasoline consumed, or per kilowatt-hour of electricity used)

energy intensity
The ratio of energy use to economic or physical output.

energy efficiency
Using less energy to provide the same service (lighting, mobility, cooling/heating, etc).

fossil fuel
A general term for organic materials formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth’s crust over hundreds of millions of years.

fugitive emissions 
Emissions that are not physically controlled but result from the intentional or  unintentional release of GHGs. They commonly arise from the production,  processing, transmission, storage and use of fuels or other substances, often  through joints, seals, packing, gaskets, etc. Examples include HFCs from  refrigeration leaks, SF6 from electrical power distributors, and CH4 from solid waste landfills.

global warming
The gradual increase, observed or projected, in global surface temperature, as one of the consequences of radiative forcing caused by anthropogenic emissions.

global warming potential (GWP)
An index measuring the radiative forcing following an emission of a unit mass of a given substance, accumulated over a chosen time horizon, relative to that of the reference substance, carbon dioxide (CO2). The GWP thus represents the combined effect of the differing times these substances remain in the atmosphere and their effectiveness in causing radiative forcing.

green power
A generic term for renewable energy sources and specific clean energy  technologies that emit fewer GHG emissions relative to other sources of energy  that supply the electric grid. Includes solar photovoltaic panels, solar thermal  energy, geothermal energy, landfill gas, low‐impact hydropower, and wind  turbines.

greenhouse effect
Trapping and build-up of heat in the atmosphere (troposphere) near the Earths surface. Some of the heat flowing back toward space from the Earth’s surface is absorbed by water vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then reradiated back toward the Earths surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase.

greenhouse gas (GHG)
Any gas that absorbs infrared radiation in the atmosphere. GHGs include carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride.

heating value
The amount of energy released when a fuel is burned completely.

in-boundary emissions 
GHG emissions released within the jurisdictional boundary of a community.  Examples include GHG emissions from natural gas combustion in household  furnaces and gasoline combustion in motor vehicles driven on roads within the  community’s jurisdictional boundary.

indirect emissions
Greenhouse gas emissions that are a consequence of the activities of the reporting entity, but occur at sources owned or controlled by another entity. For example, emissions are described as indirect to a city if they relate to the purchase of electricity that is generated outside of the boundaries of a city.

inventory
A comprehensive, quantified list of a community’s or organization’s GHG emissions  and sources.

inventory boundary
An imaginary line that encompasses the GHG emissions included in the inventory.  It results from the chosen organizational and operational boundaries.

kilowatt hour (kWh)
The electrical energy unit of measure equal to one thousand watts of power  supplied to, or taken from, an electric circuit steadily for one hour. (A Watt is the unit of electrical power equal to one ampere under a pressure of one volt, or 1/746  horsepower.)

landfill 
Land waste disposal site in which waste is generally spread in thin layers, compacted, and covered with a fresh layer of soil each day.

landfill gas
Biogas that is produced from the decomposition of organic materials within landfills.

life cycle analysis
Assessment of the sum of a product’s effects (e.g. GHG emissions) at each step in  its life cycle, including resource extraction, production, use and waste disposal.

life cycle emissions
GHG emission sources associated with all stages of the life cycle of materials,  energy, and services; includes  the “upstream” supply chain (e.g., resource extraction, production, transport), use, and end‐of‐life management (including transportation and recycling). 

liquefied natural gas (LNG)
Natural gas that has been converted to liquid form by compression at moderate pressure and cooled to -258°F. The volume of natural gas as liquid is 1/600th of its volume as gas, improving the cost and safety of non-pressurized storage or transport.

liquefied petroleum gas (LPG)
A group of hydrocarbon‐based gases derived from crude oil refining or natural gas fractionation. They include propane, propylene, normal butane, butane, butylene, isobutene A‐14 and isobutylene.

methane (CH4)
A colorless, odorless flammable gas that is the main constituent of natural gas. It is the simplest member of the alkane series of hydrocarbons. It is a greenhouse gas with a global warming potential estimated to be 96 over 20 years (GWP20) and 32 over 100 years (GWP100). The GWP100 of carbon dioxide is equal to 1.

fugitive methane emissions
A type of fugitive emission in which uncombusted natural gas, consisting primarily of methane, escapes into the atmosphere from the natural gas infrastructure system (production, processing, transmission, and distribution).

metric ton (tonne)
Common international measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2205 lbs or 1.1 short tons.

mitigation (of climate change)
A human intervention to reduce the sources or enhance the sinks of greenhouse gases.

mobile combustion
Emissions from the combustion of fuels in transportation sources (e.g., cars, trucks,  buses, trains, airplanes, and marine vessels) and emissions from off‐road  equipment such as what is used in construction, agriculture, and forestry.

municipal solid waste (MSW)
Residential solid waste and some non-hazardous commercial, institutional, and industrial wastes.

natural gas
A naturally occurring mixture of principally methane and small fractions of hydrocarbon and nonhydrocarbon gases found in porous geologic formations beneath the Earth’s surface, often in association with petroleum (oil). It is sometimes referred to as “geologic,” “fossil,” “conventional, ” or “thermogenic” natural gas to distinguish it from biomethane (“biogenic” gas)

negative emissions
Any technology that removes CO2 or other greenhouse gases from the atmosphere so as to reduce anthropogenic climate change. Examples include enhanced soil weathering, afforestation and reforestation, and enhanced primary production in the ocean.

nitrous oxide (N2O)
One of the six primary GHGs, consisting of two nitrogen atoms and a single oxygen  atom, possessing a GWP of 310, and typically generated as a result of soil cultivation practices, particularly the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.

power-to-gas (PtG, P2G)
An energy conversion process that converts electrical power to a gaseous fuel. One exampleincludes the production of hydrogen via electrolysis. Through an additional process known as ‘methanation’ hydrogen can then be converted into methane by reacting with carbon oxides.

propane
A normally straight chain hydrocarbon that boils at ‐43.67 degrees Fahrenheit and  is represented by the chemical formula C3H8.

radiative forcing 
A measure of the influence of a particular factor (e.g. greenhouse gas, aerosol, or land use change) on the net change in the Earths energy balance. Measured in units of watts per square meter (W/m2) at the top of the Earth’s atmosphere.

reforestation
Planting of forests on lands that have previously contained forests but that have been converted to some other use.

renewable energy certificates/credits (RECs)
A market tradable commodity that represents proof that one megawatt‐hour  (MWh) of electricity was generated from a third‐party verified renewable energy  resource, such as a solar renewable energy certificate (SERC) that is generated  from solar energy resource.

renewable gas
Hydrogen and methane produced from renewable electricity as well as renewable natural gas.

renewable natural gas
See biomethane

residual fuel oil
A general classification for the heavier oils, known as No. 5 and No. 6 fuel oils, that  remain after the distillate fuel oils and lighter hydrocarbons are distilled away in refinery operations.

scope(s)
a reporting framework that categorizes direct (scope 1) emissions (e.g., smoke stacks or tailpipes that release emissions  within an organizational boundary), indirect energy‐related (scope 2) emissions  (e.g., the use of purchased or acquired electricity, heating, cooling, or steam  regardless of where the energy is generated), and other indirect (scope 3) emissions not covered in scope 2 (e.g., upstream and downstream emissions from  the extraction and production of purchased materials and fuels).

scope 1 emissions
Direct emissions of greenhouse gases from owned or controlled sources. For a city, examples include emissions from energy use in buildings or from transportation within the city boundaries.

scope 2 emissions
Indirect emissions of greenhouse gases from the generation of purchased energy. For a city, examples include the emissions associated with the purchase of electricity, heat, or steam that is generated from sources outside the city boundary.

scope 3 emissions
Other indirect emissions of greenhouse gases not covered in Scope 2. Examples include the extraction and production of purchased materials and fuels, and transport-related activities in vehicles not owned or controlled by the reporting entity.

sequestration
The uptake of carbon containing substances, in particular carbon dioxide, in terrestrial or marine reservoirs.

short ton (ton)
Common measurement for a ton in the U.S. and equivalent to 2,000 pounds or  about 0.907 metric tons.

sink
Any process, activity or mechanism that removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas or aerosol from the atmosphere.

social cost of carbon
The net present value of climate damages (with harmful damages expressed as a positive number) from one more ton of carbon in the form of carbon dioxide, conditional on a global emissions trajectory over time.

stationary
Neither portable nor self-propelled, and operated at a single facility.

stationary combustion
Emissions from the combustion of fuels to produce electricity, steam, heat, or  power using equipment (boilers, furnaces, etc.) in a fixed location.

therm
A measure of one hundred thousand (105) Btu.

verification
An independent assessment of the reliability (considering completeness and  accuracy) of a GHG inventory.