GLY1073 - The Grand Finale Stella Exercise

The final Stella exercise couples the population growth, carbon cycle, and Earth energy balance models in an effort to examine the effect of future population growth and CO₂ emissions on global mean temperature. The population growth model will be used to drive the rates of fossil fuel consumption and deforestation in the carbon cycle model. The atmospheric CO₂ concentration of the carbon cycle will, in turn, be used to drive the energy balance model by affecting the atmospheric absorption coefficient.

1.) Begin with the coupled population and CO₂ model. Be sure the carbon cycle is coupled to population and energy resources. Be sure that the initial atmospheric carbon concentration is 720 Gt and that your model predicts an atmospheric CO₂ concentration of about 650 ppm after 100 years (don't worry if your result differs by +/- 10 ppm).

2.) Couple the population/carbon cycle model above to the Earth energy balance model with atmosphere. Link the CO₂ concentration (ppm) in the carbon cycle model to the CO₂ increase factor in the energy balance model. Set the CO₂ increase factor equal to CO₂ ppm/ 353 ppm.

What is the predicted global mean atmospheric temperature (in degrees Celsius) in 100 years given the present rates of population growth and CO₂ emissions? Note: You should run this model and all subsequent models with a time-step of 0.1 (DT=0.1). Which of the IPCC scenario results is closest to your answer (see graph and table below)?  What are some of the assumptions behind that IPCC scenario (for information, download report on IPCC scenarios).

3.) Please write a short paragraph describing if/how this final model helps you to visualize the linkages between humans, energy consumption, atmospheric composition, and Earth's climate system. What lessons/insights did you learn/gain from such an exercise? In general, did you find the Stella exercises useful for conceptualizing how the earth works as a system? Do you have any suggestions for how the exercises might be improved?