Download STELLA Carbon Cycle

© Climate Change 2007: The Physical Scientific Basis, Intergovernmental Panel on Climate Change.
University of Michigan Fuel links: http://sitemaker.umich.edu/section7group6/links
University of Michigan Rain Forest impact: http://sitemaker.umich.edu/section3group2/deforestation_of_the_amazon_rainforests_and_co2
Using the University of Michigan Same fuel STELLA model (assumes continuation of current fossil fuel trends), do the following.
1] Checking assumptions in the model:
Include a drawing (or printout) of the model in your notebook.
Do you notice any carbon reservoirs missing? How significant do you think they might be? See if you can find any estimates of their size from
the web.
Notice the generator (source or sink) for ocean sediments. What stock could replace this, if you wished to include it?
Are there any flows that you can think of which are not included? Are they combined as part of another flow in the model?
2] Further assumptions about parameters:
With the model up, click on the Run tab and choose Range Specs .
Notice what the ranges are and what assumptions are made concerning how they are allowed to change over time. [Are they assumed to be
constant? How wide a range are they allowed to vary through?]
3] Do the same for the biomass STELLA model which assumes a switch to biomass fuels.
What is different about the model flows?
How are the assumptions about ranges different?
4] Run the model and click on the pink graph icon. This will produce a graph of the atmospheric CO2 from the model. Do this for both graphs
and compare the two outputs. How do they differ?
Notice on the output from the Same Fuel Model. What does the graph look like; linear, smooth curve, ….? What might account for the features
shown by the graph?
5] Now you can model the impact of deforestation in the Amazon rainforest. Read the introduction document from University of Michigan and
look at the Stella Model .
6] What are the stocks in the model?
7] How sensitive are the results to the deforestation rate? Use +/- 10% to check this.
8] Where would this model link up with the other Carbon cycle models you used above?
9] If you were to link this model to the biomass fuel model, what additional loops might be necessary? You may need to search the web for
information and questions about the links between biofuels and the Amazon forest.
Carbon cycle questions:
[1] What effect does cutting the deforestation by half have on the atmospheric CO2 level?
[2] What is the effect on atmospheric CO2 of changing the Ocean uptake by +5%? By-5%?
What happens if the Ocean release is changed by the same amount in the opposite direction?
[3] Now change the Ocean uptake to 100, the Ocean release to 108 and the sediments to -.2. What happens to the atmospheric CO2 levels?
[4] By adjusting the four rates, can you produce changes which result in positive feedback situations? Remember that the greenhouse effect
says that higher atmospheric CO2 gives higher Temperature which decreases CO2 solubility in water. Also, the more CO2 dissolved in the oceans,
the more acidic they become and the lower the carbonate sedimentation rates will be.