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Glossary of Terms

What does it all mean? – Glossary of Terms

Your source for defining important terms related to Climate Change, Global Warming, and Sustainability.


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

Anthropogenic: Made by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities.

Atmosphere: The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium, radiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio), and ozone. In addition the atmosphere contains water vapor, whose amount is highly variable but typically 1% volume mixing ratio. The atmosphere also contains clouds and aerosols.


Climate Change: refers to any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). Climate change may result from:

  • natural factors, such as changes in the sun’s intensity or slow changes in the Earth’s orbit around the sun;
  • natural processes within the climate system (e.g. changes in ocean circulation);
  • human activities that change the atmosphere’s composition (e.g. through burning fossil fuels) and the land surface (e.g. deforestation, reforestation, urbanization, desertification, etc.)

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 anthropogenic greenhouse gas that affects the Earth’s radiative balance. It is the reference gas against which other greenhouse gases are measured.

Carbon Dioxide Equivalent (COe) : A metric measure used to compare the emissions from various greenhouse gases based upon their global warming potential (GWP). Carbon dioxide equivalents are commonly expressed as “million metric tons of carbon dioxide equivalents (MMTCO2Eq).” The carbon dioxide equivalent for a gas is derived by multiplying the tons of the gas by the associated GWP. The use of carbon equivalents (MMTCE) is declining.

MMTCO2Eq = (million metric tons of a gas) * (GWP of the gas)

See greenhouse gas, global warming potential, metric ton.

Carbon Footprint: The estimated emissions of carbon dioxide (CO₂) and other GHGs associated with a particular activity (e.g. a plane trip), use of your car, your family’s overall lifestyle, or use of a particular product or service. The scope of a carbon footprint analyses can vary, and may or may not include all GHGs or reflect a “life cycle” approach to quantifying “upstream” and “downstream” GHG emissions.  When it includes all GHGs, the footprint is commonly expressed in “CO₂ equivalent” (CO₂e) units. The personal carbon footprint of a typical individual in the United States is approximately 10 tons of CO₂e per year, reflecting emissions from the activities listed above that are under a person’s direct control, e.g., home energy use and personal transport. U.S. per capita emissions (calculated by dividing total national GHG emissions by total population) are more than 20 tons per year.

Carbon Neutral: The idea of helping consumers, organizations, and businesses neutralize their personal or corporate greenhouse gas  (GHG) emissions (their “carbon footprint”) by offsetting al or some of the emissions associated with their lives and activities. Terms such as “climate neutral,” “climate friendly,” “footprint neutral,” “Climate Cool TM,” and other terms are used to characterize the same concept.

Carbon Offset: The act of reducing or avoiding GHG emissions in one place in order to counteract or “offset” GHG emissions occurring somewhere else. Unlike most conventional pollutants, GHGs mix well in the atmosphere and can travel around the planet quickly. As a result, it doesn’t really matter from the standpoint of global warming mitigation where a reduction takes place. Carbon offsets are intended to take advantage of the radically different costs and practicalities of achieving GHG emission reductions by sector and geography.


Global Warming: Global warming is an average increase in the temperature of the atmosphere near the Earth’s surface and in the troposphere, which can contribute to changes in global climate patterns. Global warming can occur from a variety of causes, both natural and human induced. In common usage, “global warming” often refers to the warming that can occur as a result of increased emissions of greenhouse gases from human activities.

Global Warming Potential (GWP): is defined as the cumulative radiative forcing effects of a gas over a specified time horizon resulting from the emission of a unit mass of gas relative to a reference gas. The GWP-weighted emissions of direct greenhouse gases in the U.S. Inventory are presented in terms of equivalent emissions of carbon dioxide (CO₂), using units of teragrams of carbon dioxide equivalents (Tg CO₂ Eq.).

Conversion: Tg = 109 kg = 106 metric tons = 1 million metric tons

Greenhouse Gas (GHG): Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, but are not limited to, water vapor, carbon dioxide (CO₂), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), ozone (O3 ), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).

Greenhouse Gas Inventory: A greenhouse gas emissions inventory is an accounting of the amounts and sources of emissions of greenhouse gases attributable to the existence and operations of an institution. The completion of such an inventory provides an essential foundation for focused, effective outreach on the issue of climate change at a college or university, and the basis for institutional action to address it—in other words, it is a crucial first step toward comprehensive campus climate action efforts.


Intergovernmental Panel on Climate Change (IPCC): The IPCC was established jointly by the United Nations Environment Programme and the World Meteorological Organization in 1988. The purpose of the IPCC is to assess information in the scientific and technical literature related to all significant components of the issue of climate change. The IPCC draws upon hundreds of the world’s expert scientists as authors and thousands as expert reviewers. Leading experts on climate change and environmental, social, and economic sciences from some 60 nations have helped the IPCC to prepare periodic assessments of the scientific underpinnings for understanding global climate change and its consequences. With its capacity for reporting on climate change, its consequences, and the viability of adaptation and mitigation measures, the IPCC is also looked to as the official advisory body to the world’s governments on the state of the science of the climate change issue. For example, the IPCC organized the development of internationally accepted methods for conducting national greenhouse gas emission inventories.


Methane (CH4): A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 23 times that of carbon dioxide (CO2). Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion. The GWP is from the IPCC’s Third Assessment Report (TAR).

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.


Recycling: Collecting and reprocessing a resource so it can be used again. An example is collecting aluminum cans, melting them down, and using the aluminum to make new cans or other aluminum products.

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

Renewable Energy: see alternative energy


Short Ton: Common measurement for a ton in the United States. A short ton is equal to 2,000 lbs or 0.907 metric tons.

Sustainability: Meeting the needs of the present without compromising the ability of future generations to meet their own needs.

Sustainability in the words of TCNJ Students:

  • “The ability to sustain oneself in  the environment without exhausting the environment’s resources.”
  • “Keeping the interests of our children in mind. We should always give them a world that is good or better than ours.”
  • “Actions that don’t cause long-term damage to the planet.”


Water Vapor: The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is an important part of the natural greenhouse effect. While humans are not significantly increasing its concentration, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapor feedback. In addition to its role as a natural greenhouse gas, water vapor plays an important role in regulating the temperature of the planet because clouds form when excess water vapor in the atmosphere condenses to form ice and water droplets and precipitation.


1. glossary from the EPA: Glossary of Climate Change Terms | Climate Change | U.S. EPA