2-4: Enhanced Greenhouse Climate, Transient Climate Simulations

Unit Objectives

• To understand how future increases in greenhouse gases will cause temperatures and precipitation patterns to change.
• To understand the range and causes of uncertainty in climate models and how these relate to uncertainties in projections of economic growth.

Preparation for Online and Class Discussion

1. Read the summary information.

   Class images

   Related class images

2. Print for offline review.

3. Take the summary information quiz. Quizzes are available from your portfolio.

4. Additional Related 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.

   	How much will the climate change? (From UNEP.)
   	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, 289-305.
   	Houghton, J. T., G. J. Jenkins, and J. J. Ephraums, 1990: Climate Change, The IPCC Scientific Assessment. Cambridge University Press. p.137-154, 179-192. (skim material related to pre-class reading)

Online and Class Discussion

• Social Comments
• Knowledge-building Comments
• Ethical Comments

• Unit Problem to Ponder
• Unit exam questions from previous years
• Unit discussions from previous years

Unit Wrap-up Materials

• Group Discussion Summary:

  Summary prepared by: Meghan Buckley, Jessica Decker, Sebastien Humbert, and Jonathan Lowe

  Enhanced Greenhouse Climate, Transient Climate Simulations, and Transient Simulation

  • external forcing (e.g., greenhouse gases, solar irradiation) are allowed to gradually change
  • change is noted according to known (e.g, past measured greenhouse gas concentrations) or future projections of external forcing.
  • internal components of the climate system (e.g., oceans, ice masses, atmosphere) are allowed to change at their natural rates in response to forcing

  Purpose

  • speculation on how a transient simulation of global climate will differ from an equilibrium simulation.
  • ocean-atmosphere global climate models
  • run in transient mode
  • results confirm previous speculations

  GFDL model

  • 1850-2000 = good results re: average temperature behavior
  • ocean circulation component -> thermohaline circulation to decrease in intensity
  • increased greenhouse gas warming
  • enhanced precipitation
  • high latitude run off
  • decrease in soil moisture -> decrease in global food production

  Hadley Model : global climate

  • maps of transient climate
  • maps of various meteorological variables.
  • increase in global mean temperature
  • modest increase in global precipitation
  • National Center for Atmospheric Research
  • warming effect of enhanced greenhouse gas concentrations
  • cooling effects of sulfate aerosols
  • variations due to fluctuating solar radiation.

  The online discussion involving the results of climate models focused in two main areas. The first was concerning the sudden increases that have occurred during separate periods in the 20th century. One answer to the increases included the uses of modern technology and the energy (or fuel) it consumes. Another topic focused on the possible opportunities for the United States to help other "starving" countries who are predicted to have agricultural trouble due to the changing climate. While anticipation of such an event was evident, warning signs about the downsides of such a happening were also brought to the forefront (exhausted resources in other areas and foreign turmoil among others).

• Recommended Reading Materials

  	Global Mean Reference Height Temperature (K)(To download Adobe Acrobat Reader, go to http://www.adobie.com/prodindex/acrobat/readstep.html).
  	Why "climate change" and "global warming" are not the same thing. (From UNEP.)
  	Houghton, J.T., G.J. Jenkins, J.J. Ephraums, eds, 1990: 1990 Intergovernment Panel on Climate Change, Cambridge University Press, 137-172 and 179-193.
  	Kirshen, P. H., Fennessey, N. M. 1995: Possible Climate Change Impacts on Water Supply of Metropolitan Boston. Journal of Water Resources Planning and Management 121, 61-69.
  	Meehl, G. A., and W. M. Washington, 1993: South Asian Summer Monsoon Variability in a Model with Doubled Atmospheric Carbon Dioxide Concentration. Science 260, 1101-1106.
  	Murray, R. J., Simmonds., I. 1995: Responses of Climate and Cyclones to Reduction in Arctic Winter Sea Ice. Journalof Geophysical Research 100, 4791-4806.
  	Rind, D., R. Golberg, and R. Ruedy, 1989: Changes in Climate Variability in the 21st Century. Climate Change 14, 5-37.
  	Watkins, A. B., Simmonds., I. 1995: Sensitivity of Numerical Prognoses to Antarctic Sea Ice Distribution. Journal of Geophysical Research 100, 22,681-22,696.

• References

  	Pielke, R. A., Jr., 2001: Room for doubt. Nature 410, 151.
  	Cox, P. M., R. A. Betts, C. D. Jones, S. A. Spall, and I. J. Totterdell, 2000: Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature 408, 184-187.
  	Betts, R. A., 2000: Offset of the potential carbon sink from boreal forestation by decreases in surface albedo. Nature 408, 187-190.
  	Stott, P. A., S. F. B. Tett. G. S. Jones, M. R. Allen, J. F. B. Mitchell, and G. J. Jenkins, 2000: External control of 20th century temperatures by natural and anthropogentic forcings. Science 290, 2133-2137.
  	SCIENCE AND NONSCIENCE CONCERNING HUMAN-CAUSED CLIMATE WARMING J. D. Mahlman Geophysical Fluid Dynamics Laboratory/ NOAA, Princeton University, Princeton, New Jersey 08542
  	Current Acacia Projects
  	Gutowski, William J., G. F. McMahon, S. S Schluchter, and P. H. Kirshen. 1994: Effects of Global Warming on Hurricane-Induced Flooding. Journal of Water Resources Planning and Management, 120, 176-185.
  	Takle, Eugene S., 1998: Future Climate Change - Myth or Reality. Proceedings of the Twentieth Annual Seed Technology Conference. Iowa State University, Ames, IA.
  	Wigley, T. M. L., R. L. Smith, and B. D. Santer, 1998: Anthropogenic influence on the autocorrelation structure of hemispheric-mean temperatures. Science 282, 1676-1679.