Carbon cycle
The movement of carbon among the atmosphere, oceans, living organisms, soils, and rocks through biological, chemical, and geological processes.
Photosynthesis: The process by which plants, algae, and some microbes use light energy to convert carbon dioxide and water into organic compounds. It transfers atmospheric or dissolved carbon dioxide into living biomass.
Carbon reservoir: A part of the Earth system that stores carbon, such as the atmosphere, ocean, soil, or rocks. The cycle is described by exchanges among reservoirs of very different sizes.
Fossil fuel: Coal, petroleum, or natural gas formed from ancient organic matter and burned for energy. Burning fossil fuels transfers geological carbon into the atmosphere much faster than natural processes do.
Greenhouse effect: The warming of a planet’s surface and lower atmosphere as greenhouse gases absorb and re-emit infrared radiation. Rising atmospheric carbon dioxide strengthens this heat-trapping effect.
Earth system model: A computer model that represents interactions among the atmosphere, oceans, land, ice, and living systems. These models simulate coupled carbon transfers and their climate effects.
Cellular respiration: The process by which cells extract energy from organic molecules, releasing carbon dioxide in many organisms. It returns carbon in organic matter to the atmosphere or water as carbon dioxide.
Carbon flux: The rate at which carbon moves between reservoirs, commonly expressed as mass per unit time. Fluxes quantify transfers that change reservoir sizes.
Deforestation: The permanent or long-term removal of forest cover through land conversion or other activity. It releases stored biomass and soil carbon while reducing future carbon uptake.
Ocean acidification: The decrease in seawater pH caused mainly by ocean uptake of atmospheric carbon dioxide. Dissolved carbon dioxide changes seawater chemistry and challenges organisms that build carbonate structures.
Terrestrial carbon cycle: The exchanges of carbon among land ecosystems, soils, and the atmosphere. Land uptake varies with climate, vegetation, nutrients, and disturbance.