Independent Study, Spring 2019
• THE CARBON CYCLE •
The global carbon cycle is the series of stocks and flows of carbon through different parts of our planet. ‘Stocks’ are the amount of carbon existing in one part at a certain time, and ‘flows’ are the rate that carbon is moving from part to part continuously. At a given time about 1.8% of the earth’s surface carbon is in the atmosphere, 1.4% is in plants, less than .000001% is in animal life, 3.7% is in soils, and 93.1% is in the ocean. And additional 4.4 trillion tons is buried deep underground as fossilized carbon, approximately equal to the total amount of surface carbon (Schlesinger and Bernhardt). These stocks are the major pools of carbon on earth’s surface, and carbon in many forms moves between them at varying rates.
Before the industrial revolution carbon continuously flowed between all of the different pools except for fossil carbon. While large quantities of carbon constantly moved from the atmosphere to the ocean and from plants to soils for example, the carbon cycle was relatively balanced and each stock stayed similarly sized. When we burn fossil carbon like coal, oil, or natural gas, we add carbon to the atmosphere that was previously buried: carbon that has been separate from the modern carbon cycle for hundreds of thousands of years is released directly to the atmosphere (Schlesinger and Bernhardt, Le Quéré et al). Flows from the atmosphere to plants, oceans, and soils have not changed enough to absorb the additional carbon, so it is accumulating rapidly in the atmosphere (Schlesinger and Bernhardt).
Carbon in the atmosphere most frequently exists in the form of carbon dioxide, a greenhouse gas, it is the single largest contributing factor in climate change (IPCC). More information on atmospheric carbon can be found here.
IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp. https://archive.ipcc.ch/report/ar5/syr/
Le Quéré C., Andres R. J., Boden T., Conway T., Houghton R. A., House J. I., Marland G.,Peters G. P., van der Werf G. R., Ahlström A., Andrew R. M., Bopp L., Canadell J. G., Ciais P., Doney S. C., Enright C., Friedlingstein P., Huntingford C., Jain A. K., Jourdain C., Kato E., Keeling R. F., Klein Goldewijk K., Levis S., Levy P., Lomas M., Poulter B., Raupach M. R., Schwinger J., Sitch S., Stocker B. D., Viovy N., Zaehle S., and Zeng N. (2013) The global carbon budget 1959–2011. Earth Syst. Sci. Data, 5, 165–185 www.earth-syst-sci-data.net/5/165/2013/ doi:10.5194/essd-5-165-2013
Schlesinger W.H. and Bernhardt E.S. (2013) Biogeochemistry: An Analysis of Global Change, 3e. Academic Press.
A more thorough summary from the University of New Hampshire: http://globecarboncycle.unh.edu/CarbonCycleBackground.pdf