Climate Physics: Using Basic Physics Concepts to Teach about Climate Change (2007)

Numerous connections exist between climate science and topics normally covered in physics and physical science courses. For instance, lessons on heat and light can be used to introduce basic climate science, and the study of electric circuits provides a context for studying the relationship between electricity consumption and carbon pollution. To highlight some of these connections, this article describes a series of lessons and activities that use basic physics concepts to teach about climate change. The examples may help teachers notice and emphasize additional correlations between their own existing physics programs and climate science. In my high school physics classes, climate change provides a unifying theme for the second semester. The curriculum outline in Figure 1 shows the full range of topics I have been able to connect to climate science in recent years. I spread these lessons across the entire semester, but they could also be taught consecutively as a separate unit in a physics or environmental science class. This article first explains how I introduce and integrate basic climate topics into units on heat and electromagnetic radiation. The second part of this article explains how a unit on electric circuits provides a useful context for discussing ways to solve the problem of climate change. Explanations of specific activities are kept brief to allow for a relatively comprehensive survey of the possibilities. Heat and electromagnetic radiation The second law of thermodynamics tells us that energy naturally flows from hot things to cold things, and the Stefan-Boltzmann law states that hotter objects radiate more energy than cold ones. These two laws form the basis for a very simple model of the interaction between the Sun, Earth, and empty space (Figure 2). I generally complete the following sequence as a class demonstration to facilitate discussion. However, the experiments described could easily be conducted by small groups if safety concerns posed by hot objects are adequately addressed. To begin, place a beaker full of water on a hot plate and set the plate to low or medium. The water will warm at first but eventually will reach an equilibrium temperature. This happens because as the temperature of the water increases, the corresponding rate at which the water loses energy to the cooler surrounding air also increases. Eventually the increasing rate at which the water loses energy to its environment equals the rate at which the water absorbs energy from the hot plate, and the system reaches equilibrium. At this point, I explain that Earth and the Sun are in a similar state of equilibrium, in which the amount of energy Earth receives from the Sun is equal to the amount radiated back into space. Careful application of the Stefan-Boltzmann law, however, predicts a much lower temperature on Earth than is actually observed, so the model is incomplete. Now place a loose lid on top of the beaker. The rate at which heat leaves the beaker will decrease and the temperature will begin to increase. This temperature increase will cause the rate of heat loss to once again increase until a new, higher-temperature equilibrium is reached. I explain to my students that carbon dioxide plays the role of the lid in Earth's atmosphere, and the carbon dioxide that exists naturally in the atmosphere keeps Earth's surface warm enough to support the various life forms that students study in their biology classes. Adding another lid to better insulate the top of the beaker simulates the consequences of adding carbon dioxide to the atmosphere by burning fossil fuels--a new higher equilibrium temperature will be reached. Of course, this model is far from complete. Earth's atmosphere, surface, and oceans form a complex, interacting system. Some of these complexities are relevant, such as the fact that warming will melt reflective white ice caps or may lead to the formation of more reflective white clouds. …