Carbon Cycle Glossary of Terms

Abundance: How common an element, molecule, or isotope is within a given space, often relative to other elements, molecules, or isotopes.

Anthropogenic: Resulting from human activities.

Atmosphere: The envelope of gases surrounding Earth or other planets.

Baseline Observatory: An atmospheric observatory located far from pollution sources where continuous in-situ (in place) atmospheric measurements are being made, and/or frequent air samples are being taken for analysis in a laboratory.

Biomass: Any organic material (living or dead).

Biosphere: The community of all living organisms and the parts of the solid earth, oceans, and atmosphere on which they depend.

Biota: All of the plant and animal life in a given area.

Carbon: An abundant, nonmetallic element that forms the backbone of organic molecules which are the building blocks for all life; has an atomic number of 6; there are 3 naturally occurring isotopes: carbon-12, carbon-13, and carbon-14.

Carbon Cycle: The continuous exchange and recycling of carbon through the Earth system, from the atmosphere (mostly CO2, but also other carbon containing gases) to the biosphere (wood, biomass), to the oceans (bicarbonate ions, a component of sea salt), from fossil fuels, and to carbonate rock such as limestone and marble.

Carbon Cycle Greenhouse Gases (CCGG) Group: Part of the Global Monitoring Division of NOAA’s Earth System Research Laboratory that is primarily focused on monitoring and understanding the earth’s carbon cycle.

Carbon Dioxide (CO2): A colorless, odorless gas consisting of molecules made up of two oxygen atoms and one carbon atom; a greenhouse gas.

Carbon Monoxide (CO): A colorless, odorless, and toxic gas consisting of molecules of one oxygen atom and one carbon atom; results from inefficient combustion or chemical reactions occurring in the atmosphere.

Carbonic Acid: A weak acid created by the dissolution of carbon dioxide into water, has a chemical formula of H2CO3.

CarbonTracker: A computer model that calculates carbon dioxide uptake and release at the Earth’s surface over time in such a way that they are consistent with a global set of observations of the CO2 abundance in the atmosphere.

CO2 Weather: A loose term referring to the movement of air masses with high- or low-concentrations of CO2 across a continental-scale region; these atmospheric CO2 patterns are caused by sources and sinks at the surface, and change with the winds, following weather dynamics before slowly fading through gradual mixing of air masses.

Climate: The weather conditions including temperature, precipitation, and wind, averaged over a long period, which characteristically prevail in a particular region during a specific month, season, or entire year.

Climate Change: A significant and lasting change to the state of the climate in a given area; typically this change occurs gradually due to natural variations, but change may also be forced more rapidly due to human activities which alter the composition of the atmosphere, the land surface, or ecosystems; although often used interchangeably with the term “global warming,” climate change can refer to other changes (e.g. changes in precipitation) in addition to rising temperatures.

Concentration: The amount of a substance in a defined volume of space.

Convection: Large scale motion caused by density differences; for example, in the atmosphere, air that is warmed at the surface expands, making it less dense--it then rises through the surrounding colder air as a large “bubble,” moving heat and water vapor to higher altitudes.

Cooperative Global Air Sampling Network: A global observing system which collects air samples on a regular basis, part of NOAA’s Earth System Research Laboratory.

Decomposition: The process of break-down that occurs after the death of living organisms, also called rotting or decay.

Deforestation: The removal, usually by cutting or burning, of forests.

Earth System: A name describing the earth as a system of interacting and interdependent components, including atmosphere (air), biosphere (life), hydrosphere (water), and lithosphere (stone).

Electromagnetic Spectrum: The range of different types of radiation as characterized by wavelength and level of energy; in order of increasing wavelength (corresponding to decreasing energy content): X-rays, ultraviolet, visible light, infrared, microwaves, radio waves.

Enhanced Greenhouse Effect: The amplified Greenhouse Effect due to human activities that increase the concentration of Greenhouse Gases within Earth’s atmosphere.

Fossil Fuels: Carbon-containing fuels, including coal, oil, and natural gas, that formed over hundreds of millions of years from the remains of living organisms.

Flux: The amount of mass flowing between two places, which can be in one direction or in both directions; for example, CO2 from the atmosphere entering the ocean, and vice versa; also often used in engineering to describe the rate of flow of liquid or gas through pipes.

Global Warming: An increase in the average global temperature brought about by the enhanced greenhouse effect.

GLOBALVIEW: A compilation of atmospheric greenhouse gas measurements, used to help understand and visualize greenhouse gas distributions (in both space and time).

Greenhouse Effect: A process which warms the earth’s atmosphere due to the absorption of radiation energy by several trace gases; these greenhouse gases allow solar radiation to reach the earth’s surface but then absorb the energy as it is reemitted as infrared radiation, acting to contain the heat within the atmosphere; this occurs naturally and is increased by humans (see Enhanced Greenhouse Effect).

Greenhouse Gases (GHGs): Gases present in the Earth’s atmosphere that contribute to the Greenhouse Effect due to properties which absorb and emit infrared radiation.

Industrial Revolution: The transformation which occurred first in many Western countries, including the United States, in the 1800s, characterized by coal burning, steel making, mass production, and rapid technical advances; marked as the beginning of strong increases in fossil fuel use.

Infrared Radiation: Long-wave (lower energy) radiation emitted by all objects at ambient temperature, including Earth’s surface; defining the infrared range of the electromagnetic spectrum.

Interactive Atmospheric Data Visualization (IADV): A web-based data exploration tool for the atmospheric trace gases measured by NOAA’s Carbon Cycle Greenhouse Gases Group.

Isotope: Atoms of the same element, but with different masses; the number of protons and electrons are the same, but the number of neutrons differ; isotopes of an element all react chemically in the same way, but the rate of reaction is slightly different, resulting in isotopic fractionation.

Isotopic fractionation: A change in isotopic ratio during a reaction or physical process (such as evaporation or freezing); for example, when CO2 is photosynthesized by plants, fractionation occurs, so that the carbon-12 to carbon-13 isotopic ratio of the carbon taken into the plant is different than that in atmospheric CO2.

Isotopic ratio: The ratio of two different isotopes of a single element in a mixture; usually measured in units of permil (‰); certain materials have characteristic isotopic ratios that can be used to identify the source.

Marine Biosphere: The community of all organisms living in the oceans and the oceans on which they depend.

Methane (CH4): A colorless, odorless, non-toxic, flammable gas consisting of molecules made up of four hydrogen atoms and one carbon atom; a greenhouse gas.

μmol mol-1, or micromol mol-1: A unit of concentration used to express the abundance of certain trace gases within the atmosphere; micro is one millionth, so μmol mol-1 is also called parts per million (ppm); For example, 401 ppm of CO2 means that in every 1,000,000 molecules of air (including CO2 itself) there are on average 401 molecules of CO2.

Nitrous Oxide (N2O): A colorless, non-flammable gas consisting of molecules made up of two nitrogen atoms and one oxygen atom; a greenhouse gas.

Organic Matter/Organic Material: Anything living or derived from living things, including the dead remains; containing the long chains of carbon atoms characteristic of living things.

Oxygen: An abundant, nonmetallic element that has an atomic number of 8; gaseous oxygen is a colorless, odorless molecule consisting of two oxygen atoms that comprises 21% of Earth’s atmosphere.

Parts Per Million (PPM): see μmol mol-1.

Photosynthesis: The process by which plants use the energy from sunlight to convert carbon dioxide into organic material, allowing them to grow.

Preindustrial: Before the Industrial Revolution.

Radiation: Energy in the form of electromagnetic waves or particles.

Radiation Budget: The accounting of radiation which enters and leaves Earth’s atmosphere.

Reservoirs: In the context of the carbon cycle, the interconnected areas within the Earth System which store and exchange carbon; includes the atmosphere, the oceans, the terrestrial biosphere, and fossil fuels.

Respiration: The process by which living organisms convert organic (carbon) material into energy needed for living, by taking up molecular oxygen and the releasing of carbon dioxide to the atmosphere.

Silicate Weathering: the erosion of rocks containing silicate minerals due to weather, ultimately removing carbon dioxide from the atmosphere over long time periods as carbonic acid in rainwater reacts with silicate rocks to create bicarbonate ions which are then carried to the oceans.

Sink: In the context of the carbon cycle, any process by which carbon dioxide is removed from the atmosphere; sinks may be natural (e.g., photosynthesis and reforestation, dissolution in ocean water) or due to human activities (e.g., managed forests and other carbon capture strategies).

Solar Radiation: Energy emitted by the sun composed mostly of visible and ultraviolet light.

Source: In the context of the carbon cycle, any process by which carbon dioxide is added to the atmosphere, sources may be natural (e.g., soil and plant respiration) or due to human activities (e.g., combustion of fossil fuels and deforestation).

Sulfur Hexafluoride (SF6): An extremely potent greenhouse gas made by humans, and used mostly as an electrical insulator during high voltage transmission of electricity.

Terrestrial Biosphere: The community of all organisms living on the land and the land surface features on which they depend.

Time Series: Measurements of a quantity collected over a period of time.

Trace Gases: Gases which together make up less than 0.1% of the atmosphere.

Ultraviolet (UV) Light: Shortwave radiation within the ultraviolet range of the electromagnetic spectrum; lies beyond the visible spectrum of light and contains wavelengths of approximately 200-400 nanometers; is harmful to most organisms.

Visible Light: Radiation within the range of the electromagnetic spectrum that is visible to the human eye; wavelengths of visible light range from approximately 400-700 nanometers.

Water Vapor: Water in its gaseous state which accounts for 0-3% of the composition of the atmosphere; the most abundant greenhouse gas; humans exert no significant control over its abundance.

Wavelength: The distance between two consecutive peaks of a wave.

Weather: Instantaneous atmospheric conditions which include temperature, precipitation, and wind; climate is the long-term average of weather.