Carbon

The carbon cycle and its alteration by human activities have become a major scientific concern over the last decade. Carbon is an element that is essential to life, and it cycles through Earth's spheres via processes such as respiration, decomposition, and combustion. Plants use carbon dioxide (CO₂) from the air to build organic carbon, which then travels up the food chain as plants are eaten. In this sense, carbon is a building block of every plant and animal on the planet.

With the course of human history, carbon has received a new starring role--providing a harnessable form of energy. Furthermore, some forms of carbon, such as carbon dioxide and methane, are greenhouse gases and intrigue scientists because of their function in climate change. To explore carbon's role in natural and human activities, take a look below at some key topics and questions.

Greenhouse Gases

How much carbon is human activity adding to the atmosphere?

play Mike Apps :
Can planting trees counter our carbon out-put ?

Human Interactions/Societal Needs

How do scientists monitor global change?

play Pam Matson :
What does the biosphere breathing look like?

Regional & Global Effects

Does tropical deforestation impact the rest of the world?

play John O. Niles :
How much carbon dioxide can a tropical forest...

Carbon /ˈkär-bĕn/ 1. a chemical element with the atomic number of 6 and that has common naturally occuring compounds.

image credit: "anthracite coal." USGS, public domain

United States Global Change Research Program Definition of Carbon

The Carbon Cycle

Definition The path through which carbon is exchanged between the Earth's spheres (hydrosphere, cryosphere, lithosphere, biosphere, atmosphere).

Summary Carbon is important as the basis for the food and fiber that sustain and shelter human populations, as the primary energy source that fuels economies, and as a major contributor to the planetary greenhouse effect and potential climate change. Carbon dioxide (CO2) is the largest single forcing agent of climate change, and methane (CH4) is also a significant contributor. Atmospheric concentrations of CO2 and CH4 have been increasing for about two centuries as a result of human activities and are now higher than they have been for over 400,000 years. Since 1750, CO2 concentrations in the atmosphere have increased by 30% and CH4 concentrations in the atmosphere have increased by 150%.

Research Questions 1. What are the magnitudes and distributions of North American carbon sources and sinks on seasonal to centennial time scales, and what are the processes controlling their dynamics? 2. What are the magnitudes and distributions of ocean carbon sources and sinks on seasonal to centennial time scales, and what are the processes controlling their dynamics? 3. What are the effects on carbon sources and sinks of past, present, and future landuse change and resource management practices at local, regional, and global scales? 4. How do global terrestrial, oceanic, and atmospheric carbon sources and sinks change on seasonal to centennial time scales, and how can this knowledge be integrated to quantify and explain annual global carbon budgets? 5. What will be the future atmospheric concentrations of carbon dioxide, methane, and other carbon-containing greenhouse gases, and how will terrestrial and marine carbon sources and sinks change in the future? 6. How will the Earth system, and its different components, respond to various options for managing carbon in the environment, and what scientific information is needed for evaluating these options?

Source: Climate Change Science Program, and The Subcommittee Global Change Research. "Our Changing Planet: The U.S. Climate Change Science Program for Fiscal Year 2006." Washington: Climate Change Science Program Office, 2006.

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Carbon

How much carbon is human activity adding to the atmosphere?

How do scientists monitor global change?

Does tropical deforestation impact the rest of the world?

The Carbon Cycle