EE/GG 275

Fall 2003

Lab 5

A MODELING THE CARBON CYCLE

Purpose

You will construct a computer-based simulation of a simplified carbon cycle.  After recreating the model discussed in class you will extend the model by:

  1. Updating the flow that represents carbon emitted due to burning of fossil fuels and carbon emitted due to deforestation.
  2. Convert the carbon in the atmosphere to carbon dioxide using relative molecular weights.
  3. Add a temperature component and forecast, based on carbon accumulation in the model, how much global temperature will increase over the next 50 years.

 

Introduction

The carbon cycle is one of the most important biogeochemical cycles because:

1.     Carbon is the key element of life.  In its reduced form as organic carbon it comprises 45-50% of the mass of all plants and animals. 

2.     Without it we would not have fossil fuels - basic food or anything.

3.     And in its oxidized form - as in CO2 - it is the most important elements in the atmosphere determining the temperature and climate on earth.  That is the greenhouse effect!

Thus it is important to understand the dynamics between the different reservoirs of carbon, what is it that leads to an accumulation in the atmosphere.

Assumptions:

Use the model and the assumptions given in the paper "Atmospheric Cycles: Simplified Carbon Cycle".  You can either do this in Stella or in Excel, but be careful how you modify the "season" variable if you use Excel.

Essentially recreate the model and run it for 50 time-periods (years), with a DT of 0.25. Graph the total accumulation of carbon in the various reservoirs - this graph you do not need to hand in Ð just for your own assurance that you created the model correctly.


Questions/Task:

1. Update the values from actual data you collected this weekend used for carbon flowing from the burning of fossil fuels, and from deforestation. Graph the total accumulation of carbon in the various reservoirs over the course of the next 50 years and interpret the results. Include the graphs in your lab report.

2. Since climate change is associated with carbon dioxide, and most of the carbon in the atmosphere is in the form of carbon dioxide, please convert carbon to carbon dioxide, using relative molecular weights (C=12, O=16). Simply create a new converter called carbon dioxide and estimate the new carbon value for the next 50 years.  Explain your conversion formula.

3. The IPCC mid-range climate sensitivity scenario demonstrates that 100% increase (doubling) in carbon dioxide concentration will increase global average temperature by 2.5 degrees Celsius.  Incorporate this information into your model, such that you estimate the change in global average temperature as a function of carbon accumulation. Assume that the current average global temperature is 15 degrees Celsius.   Thus, you need to create a new model component where you estimate the change in carbon dioxide levels and relate that then to a change in temperature (which is a stock!). Graph the annual average global temperature and include in your lab report. Given your model, what will average global temperature be in the year 2050?

Make sure that in your lab report you explain the math behind the new model component.  

4.     Given your results discuss whether the changes in global temperature seem reasonable (e.g. are they in line with what IPCC scenarios state?). How would you change the model to make the results more realistic? 

Write a lab report addressing all the factors discussed before. Make sure you include the conceptual model, but in the quantification part you only need to include the part you developed yourself - simply state "see handout" for the rest of the formulas.