The topic of global change presents significant challenges to teaching. Students approach the subject matter with pre-(mis-)conceptions related to many of the “building block” concepts as well as the more complex subject matter of the interdependence of earth processes that produce global change. Interdependence of processes and the concepts of different spatial and time scales are difficult to grasp. Media coverage of this topic is extensive and problematic. Many of the popular media presentations related to global change include inappropriate use of model predictions, inaccurate representations of physical processes, false associations of unrelated phenomena, and use of emotion-laden language. Techniques need to be developed to enable students to confront these preconceived ideas as they construct their understanding of the topic.
A sampling of these challenges (undoubtedly just the tip of the iceberg) to learning about global change is presented here.
Conceptualizing relevant processes: Making Visible the Invisible
The challenges of teaching some of the basic science content related to global change are numerous. Many processes - those involving atmospheric gases, for example - cannot be directly sensed by humans. The study of fluids - atmosphere and ocean - is filled with difficulties of visualization, counter-intuitive effects and complex scale interactions. Transformation and redistribution of energy also requires students to form abstract concepts and to appreciate the global scale along with the more accessible local effects. Tools which enable students to better visualize or to gain direct experience with these phenomena would increase their ability to understand the system.
Importance of scales
Global change is often represented by one number, the change in global average surface temperature. This is misleading, as this number may not be representative of any single place on earth, nor may it be the most significant parameter to characterize specific local effects. Change is manifested on the local scale; local change is evaluated for the globe and over time. Forcing is also scale-dependent. Students can benefit from exploration of the connection between local and global scale, from evaluating the interactions between processes at different spatial and temporal scales, and by examining model predictions at various scales.
Natural variability, human impact and global change
The earth system is dynamic and has experienced dramatic change over time. In the absence of human impact, the climate has both warmed and cooled, species have appeared and become extinct and land cover has changed. Human activity currently has a significant impact on the earth system. How does it compare with known natural variability? In the past, and in the future? (Paleontologist Peter Ward says that the disappearance of the greatest number of species from earth has resulted from two types of catastrophic events: comet bombardment and the dawn of man).
Understanding the natural variability of the system, both on the long and short time scales, leads to greater understanding of the effects of human activity on the earth. Assessment of long-term global trends is not a simple extrapolation of short-term changes. Students will benefit from exploration of the statistical relationships between long- and short-term trends, natural variability, and effects of human impact on that variability. These phenomena can be introduced simply in the K-12 curriculum.
Predicting global change
Numerical models are used to explore the earth system, examine interdependent processes and scale-dependencies within the system, and make predictions about future states of the system. These computer models, from the simple to the complex, are useful in enabling students to build successful mental models of the earth system and its component processes. Students who have access to model-building tools learn about the earth system while acquiring experience with the advantages and limitations of using computer-based (or VR) models to represent real world processes. Model building enables understanding of the dominant processes in the system, and the ways in which those processes interact to affect the outcome. Using a ready-made model can also help to build understanding of system response to various levels of forcing.
It is important that students learn about model limitations - that computer models reflect at best the “state of the art” knowledge of the phenomena represented in the model; that the accuracy of model predictions is limited by the level of sophistication of the model processes and by the data used to initialize it; that continuous variables are represented by values at discrete points; etc.
Selective absorption of radiation by gases in the atmosphere, or the greenhouse effect, is a major concept that involves several common misconceptions. Complex interdependence of oceanic and atmospheric circulations, and land cover feedback onto earth’s radiation budget are also fundamental concepts that students typically struggle to grasp. (We need to be aware that a new visualization or immersion tool - VR - may also introduce new misconceptions).
Since many students will enter the classroom with ideas gained from popular media or discussions with parents and others who have been exposed to these information sources, it is important to address some of the major misconceptions prevalent in this domain. One of the most widespread problems is the false association of unrelated phenomena - the confounding of the ozone hole and the greenhouse effect, for example. Another problem is the assignment of values to physical phenomena: the greenhouse effect and radiation are “bad”; ozone is “good” (and this is doubly complicated because of the various roles that ozone plays in the atmosphere).
Media presentations are often based on simple answers or analyses of processes that are by nature complex. It is best to confront students with this in a straightforward way, and provide tools that allow them to explore the complexities of the system and assess the probability of the existence of simple answers.
Global vs. local/personal perspectives
Global change curricula must address at some level the issue of personal responsibility and action. Students who are engaged in earnest reflection on this issue may become truly distressed by it. They will need to focus on solutions that they can relate to. A model building tool that can be used to predict the success of remedial action would be a powerful way for students to visualize the potential effects of their impact projected onto global scale phenomena.