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Authors: Kathleen Merrigan, Ph.D., William Lockeretz, Ph.D.

Readings

Atmosphere. 2. Stratospheric Ozone depletion. EPA (no date).

The Potential of US Cropland to Sequester Carbon and Mitigate the Greenhouse Effect. Chaps. 2, 3 and 11. R. Lal et al. (1999)

Contributions of agro ecosystems to global climate change. J.W. Duxbury et al. Chap.1 in Agriculture Ecosystem Effects on Trace Gases and Global Climate Change. (1993)

Key Questions

Stratospheric Ozone Depletion

  • What are the causes and implications of stratospheric ozone depletion?

The Potential of US Cropland to Sequester Carbon and Mitigate the Greenhouse Effect

  • Why is radiative forcing of Greenhouse gases (GHG) expressed in terms of MMTCE (million metric tones of carbon equivalents)? For the same purpose, which is the more widely used unit internationally?
  • Which gas is most important among all GHGs? What is the major trend projected with reference to this gas?
  • How does agriculture contribute to the release of GHGs?
  • How much does agriculture contribute to the overall anthropogenic emission of GHGs in the World?
  • How much does US contribute to global mission of GHGs?
  • How much does agriculture contribute to the overall anthropogenic emission of GHGs in the US?
  • What options would allow reduction of GHGs from US agriculture?
  • What are some of the practices that allow for better soil carbon sequestration on US croplands? Which practice presents the greatest opportunity?
  • What factors hinder soil carbon sequestration?

Contributions of Agro Ecosystems to Global Climate Change

  • What are the global trends with reference to concentration of carbon dioxide, methane and nitrous oxide in Earth’s atmosphere?
  • What factors are considered while calculating the global warming potential (GWP) of a GHG?
  • What are the direct and indirect effects of methane which contribute to global warming?
  • How does the GWP of methane compare with that of carbon dioxide?
  • How does the GWP of nitrous oxide compare with that of carbon dioxide?
  • Why is nitrous oxide a more effective GHG over a long period of time compared to methane?
  • How closely is the generation of carbon dioxide, methane and nitrous oxide dependent on human activities?
  • What are the sources and sinks of carbon dioxide, methane and nitrous oxide?

Supplementary Readings

Electromagnetic Spectrum http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

Emission Facts: Metrics for Expressing Greenhouse Gas Emissions: Carbon Equivalents and Carbon Dioxide Equivalents http://www.epa.gov/otaq/climate/420f05002.htm