Carbon Cycle



Lessons and Activities

Real World Data

Background Information

Take a bite of dinner, a breath, or a drive in a car - you are part of the carbon cycle - moving carbon from one reservoir to another.

Reservoirs in the Climate Cycle
This diagram shows some of the carbon cycle's land and ocean processes.
Source: NOAA (Featured in ESRL's Carbon Cycle Toolkit)

Carbon is the chemical backbone of life on Earth, a key element in many important processes. Carbon compounds help to regulate the Earth’s temperature, make up the food that sustains us, and provide a major source of the energy to fuel our global economy. Most of Earth’s carbon is stored in rocks and sediments, while the rest is located in the ocean, atmosphere, and in living organisms - these are the reservoirs through which carbon cycles.

Carbon Storage and Exchange

Carbon moves from one storage reservoir to another through a variety of mechanisms. One example is the movement of carbon through the food chain. Plants move carbon from the atmosphere into the biosphere through photosynthesis: they take in carbon dioxide and use energy from the sun to chemically combine it with hydrogen and oxygen to create sugar molecules. Animals that eat the plant can digest the sugar molecules to get energy for their bodies. Respiration, excretion, and decomposition release the carbon back into the atmosphere or soil continuing the cycle.

The ocean plays a critical role in the storage of carbon, as it holds about 50 times more carbon than the atmosphere. Two-way carbon exchange can occur quickly between the ocean’s surface waters and the atmosphere, but carbon may also be stored for centuries at the deepest ocean depths.

Rocks such as limestone and fossil fuels such as coal and oil are storage reservoirs that contain carbon from plants and animals that lived millions of years ago. When these organisms died, slow geologic processes trapped their carbon and transformed it into these natural resources. Processes such as erosion release this carbon back into the atmosphere very slowly while volcanic activity can release it very quickly. Burning of fossil fuels in cars or power plants is another way this carbon can be released into the atmospheric reservoir quickly.

Changes to the Carbon Cycle

The increasing human population and their activities have a tremendous impact on the carbon cycle. Burning of fossil fuels, changes in land use, and the use of limestone to make concrete all transfer significant quantities of carbon into the atmosphere. As a result the amount of carbon dioxide (CO2) in the atmosphere is rapidly rising and is already significantly greater than at any time in the last 800,000 years. This increase of CO2 is affecting our ocean as it absorbs much of the CO2 that is released from burning fossil fuels. This extra CO2 is lowering the ocean’s pH, this process is called ocean acidification and interferes with the ability of marine organisms (such as corals) to build their shells and skeletons.

Education Connection

All of our daily activities impact the carbon cycle. The resources in this collection provide real world examples of the changes occurring in the cycle. There is much to learn about this essential topic and some of the resources highlight exciting career opportunities in this field of study.

Introductory text compiled from resources provided by NOAA's Office of Oceanic and Atmospheric Research

Page Last Updated 2/28/2011

NOAA Research Airplane
Hunting For Carbon Over Alaska

August 2009 (NOAA)
Billions of tons of carbon are buried in the frozen Arctic tundra, now heating up because of human-caused climate change. In the future, will the warming tundra dry out, exhaling large amounts of heat-holding carbon dioxide?... Read More

 N. America map showing reduced carbon dioxide absorption
Drought Impacts Carbon Storage

November 2007 (NOAA)
The widespread drought and heat wave that struck Europe in 2003 left more than 500 million tons of extra carbon in the air that year. "Disruptions to natural carbon uptake can have enormous environmental and economic effects, possibly even erasing efforts to reduce fossil fuel emissions in a given year," says Peters.... Read More

Historic National Weather Service Photo
1955 Article about Carbon in the Atmosphere

1955 (NOAA)
Important climatic effects are attributed to this small percentage of carbon dioxide in the air, and, according to Callendar and Plass, a significant increase in the concentration of CO2 would noticeably raise the surface temperature of the earth because of the "greenhouse effect."... Read More