STELLA MODELING AS A TOOL FOR UNDERSTANDING EARTH SYSTEMS

Among the challenges of teaching Earth System Science (ESS) is helping students understand the dynamics of complex systems. Modeling (constructing and experimenting with) systems in STELLA (www.hps-inc.com) is an accessible tool for developing the kind of intuitive grasp of systems needed for a richer understanding of Earth systems. Furthermore, the process of constructing models leads to a mode of inquiry that can reveal useful insight into the real world systems of interest — what are the essential components of the system, how are they related, what are the key processes and how can they be represented mathematically, where are the key feedbacks?

By initially working with very simple systems, focusing on concepts like feedback mechanisms, response times, steady-state, oscillations, etc., students learn about the general behavior of systems. A key part of this experiential learning consists of making predictions (and discussing them in small groups) about the behavior of the system before running the models and then evaluating the predictions in light of the results. The next step is to move on to larger, more complicated models representing important earth systems. Exploring these systems through modeling can result in a deeper understanding of the systems and provides an opportunity to explore questions about the significance of model results. For instance, students can clearly learn a great deal by constructing and experimenting with a global carbon cycle model, but this leads to the question of the extent to which we can trust the models results. The model can be tested by configuring it to represent the pre-industrial state and then inputting the history of emissions from burning fossil fuels, comparing the model’s results with the observed record of atmospheric CO2 over the same time span. This kind of model testing helps students think about the significance of model results.

The result of this kind of modeling is an improved intuitive grasp of system dynamics, a deeper understanding of particular earth systems (gained primarily by constructing the model), and a more sophisticated sense of how to interpret model results. An extensive tutorial on modeling earth systems with STELLA is available at www.acad.carleton.edu/curricular/GEOL/DaveSTELLA/entrance.html