There is 30 percent more carbon in the atmosphere today than there was 150 years ago. The first lesson in the four-part series teaches classes about the carbon cycle. Over two to three days, classes make a model of the cycle, add missing components after viewing other models, and finish by playing a game. Taking on the role of a carbon atom, they work their way through the cycle by flipping a coin to move. The lesson ends with a discussion based upon their experiences.