2-3: Climate Model Results - Equilibrium Models

Unit Objectives

• To understand the difference between equilibrium simulations and transient simulations of climate.
• To determine how well models can simulate the present observed climate.

Preparation for Online and Class Discussions

1. Read the summary information.

   Class images

   Related Unit 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.

   	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, 246-275.
   	Houghton, J. T., G. J. Jenkins, and J. J. Ephraums, 1990: Climate Change, The IPCC Scientific Assessment. Cambridge University Press. p.99-123.
   	Houghton, J.T., G.J. Jenkins, J.J. Ephraums, eds, 1990: 1990 Intergovernment Panel on Climate Change, Cambridge University Press, 80-91.

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:

  Discussion Summary Prepared by:

  Summary Information

  There are many different kinds of global climate models, and while each does a respectable job at predicting some global trends, no one model is able to successfully predict all of them. The climate models must include oceans, ice masses, land messes, the atmosphere, and the biosphere. The effects of each, and the interactions between them, must be taken into account in order to create a successful model.

  Ocean and atmospheric circulation models have proceeded along the same path. They use many of the same basic equations, though variables obviously change. Though difficult, scientists have been able to successfully combine these two important models.

  Global models show general trends, but are not accurate in predicting local and regional temperatures and precipitation. Soil moisture and snow cover are reasonably well modeled, but have shortcomings. Models do well in tracking slow changes, such as El Nino and volcanic eruptions. Ocean and atmosphere-ocean models generally perform well.

  It has been decided that the models are successful enough in predicting climate changes that they can be used to predict effects of increased levels of greenhouse gases.

  Models are also used to run a 2XCO2 model, which shows the effects of a constant rate of CO2 at twice pre-Industrial Revolution levels. The 2XCO2 models show increases in both temperature and precipitation.

  Both models show more substantial warming in the northern polar regions than in other areas. The GFHI model show more warming at the North Pole and less difference in warming between land and water regions at high latitudes. The models both predict small increases in the tropics, but disagree on warming over Antarctica.

  Several models were compared at predicting certain values over the United States. On mean January temperatures, most models were within 2 degrees Celsius of observed. Some models overpredicted the temperature at higher latitudes. On mean July temperature, the models varied widely, giving values either too high or too low for different regions. The 2XCO2 models show somewhat similar results, though the predicted temperatures are higher in higher latitudes. Because of large errors in precipitation models, the values are not accepted as accurate predictions.

  Online discussion

  The online discussion arose from the problem to ponder. It focused on why 2XCO2 and 4XCO2 levels are often used as levels on which to run global climate models. Some thought the 2XCO2 levels were for shorter time scales, under a century, while the higher level is for many centuries in the future. Another thought was the 2XCO2 level was what would happen if we cut emissions by half, while the 4XCO2 would result if we continues business as usual.