1-5: Carbon Cycle, Methane

Pre-Class Preparation

Objectives

To understand the role of carbon compounds in the earth's atmosphere and how they are linked to biosphere processes.
To examine changes in atmospheric carbon compounds and how humans have contributed to these changes.

Procedure

Read the learning unit.
Class images
Take the learning unit quiz. Quizzes are available from your portfolio. You may access your portfolio via the list of students participating in this year's course, as represented by the icon below.

Additional Required Reading. Although you are not ultimately responsible for content listed in this section, we encourage you to fully explore the links in order to provide a better scope on the upcoming class discussion.

	Boreal Forest Area as a Source of Carbon Dioxide
	CO₂ Emissions and the "Missing Carbon" Problem. (From UNEP.)
	Emissions of Methane from Livestock. (From UNEP.)
	Fuel and the Carbon Cycle. (From UNEP.)
	Methane Emissions From Rice Cultivation. (From UNEP.)
	Houghton, J. T., G. J. Jenkins, and J. J. Ephraums, 1990: Climate Change, The IPCC Scientific Assessment. Cambridge University Press. p. 18-23/

Class Discussion

Problem to ponder...
On average, each man, woman, and child in the US puts 19,000 kg of carbon dioxide into the air per year due to the burning of fossil fuels. If this carbon dioxide is taken out at a decreasing exponential rate given by
X(t) = X_o e^-t/T

where X_o is the original 19,000 kg, t is the number of years after X_o is emitted, and T is 90 years, then how much of the 19,000 kg of carbon dioxide you put into the atmosphere in 1998 due to burning of fossil fuel will remain in the year 2000? How much will be left in 2050? 2100? 2500?
Class Discussion Summary: by class members Seth Holmen and Scott Lyman

The discussion on Friday, January 23rd was over the unit block dealing with the carbon cycle. The current level of CO₂ in the atmosphere is 360 ppm. The increase of CO₂ is mainly due to the burning of fossil fuels which is known by the increase of the ratio of C12 to C14 in the atmosphere. The biosphere adjusts to abrupt changes in CO₂ only after many hundred years. Cultivated land has 1/2 the carbon than that of native land. Swamps and marshes have the highest levels of soil carbon. Although methane is in much less concentration than CO₂, it has approximately 20 times the strength. Therefore, CH4 absorbs much more radiation than CO₂. The lifetime of methane is only approximately 10 years opposed to a few hundred.

Post-Class Activities

Participate in the electronic dialog. Use this forum for:

continuing class discussion;
posing new questions to students or the instructor;
responding to issues/questions raised by students in class/electronic dialog.

Visitor Access (Visitors are welcome to participate in the dialog. Just click on the icon below)	Student Access (Students must post all dialog from their portfolio. Click on the icon below to access the student list.)

Recommended Reading Materials

	An Elementary Discussion of Ocean Carbon. (From Sea WiFS: Studying Ocean Color From Space).
	Fact Sheet: Greenhouse Gases and Global Climate Change.
	Sass, R.L. Mitigation of Methane Emissions from Irrigated Rice Agriculture.
	Why Cement-making Produces Carbon Dioxide. (From UNEP.)
	Berner, R.A., 1990: Atmospheric Carbon Dioxide Levels over Phanerozoic Time. Science, 249, 1382-1386.
	Birks, J.W., J.G. Calvert, R.E. Sievers, eds, 1992: The Chemistry of the Atmosphere: Its Impact on Global Change: Chemrawn VII Perspectives and Recommendations. The Agency for International Development, 163 pp.
	Fraser, P. J., et al., 1986: Termites and Global Methane: Another Assessment. Journal of Atmospheric Chemistry, 4, 295-310.
	Houghton, J.T., G.J. Jenkins, J.J. Ephraums, eds, 1990: 1990 Intergovernment Panel on Climate Change, Cambridge University Press, 78-82.
	Houghton, J. T., L. G. Meira Filho, B. A. Callander N. Harris, A. Kattenberg, and K. Maskell, 1996: Climate Change 1995.The Science of Climate Change. Cambridge University Press, 78-82.
	Johnson, K. A., et al. 1995: Methane Emissions from Cattle. Journal of Animal Science, 73, 2483-2492.
	Kerr, R., 1994: Methane Increase Put on Pause. Science, 263, 751.
	Phillips, D.E., A. Wild, and D.S. Lenkinson, 1990: The Soils Contribution to Global Warming. Geographical Magazine, April, 36-38.
	Post, W.M. T.S. Peng, W.R. Emanuel, S.W. King, V.H. Dale, and D.L. DeAngelis, 1990: The Global Carbon Cycle. American Scientist, 78, 310-326.
	Seiler W., et al. 1984: Field Studies of Methane Emission From Termite Nests Into the Atmosphere and Measurement of Methane Uptake by Tropical Soils. Journal of Atmospheric Chemistry, 1, 171-186.

References

	Tans, P. P., and J. W. C. White, 1998: In balance, with a little help from the plants. Science 281, 183-184.
	Falkowski, P. G., R. T. Barber, and V. Smetacek, 1998: Biogeochemical controls and feedbacks on ocean primary production. Science 281, 200-206.
	Duarte, C. M., and S. Agusti, 1998: The CO₂ balance of productive aquatic ecosystems. Science 281, 234-236.
	Field, C. B., M. J. Behrenfeld, J. T. Randerson, and P. Falkowski, 1998: Primary production of the biosphere: Integrating terrestrial and oceanic components. Science 281, 237-240.
	Glossary: Carbon Dioxide and Climate
	Abrams, Joel: Forests as Carbon Sinks
	The Biology Department at Whitman College.
	Global Emissions Inventory Activity-- annual CO₂ emissions world map.
	Kling, G. W., et al., 1991: Arctic Lakes and Streams as Gas Conduits to the Atmosphere: Implications for Tundra Carbon Budgets. Science, 251, 298-301.