Abstract

The greenhouse effect is taught in a variety of different Earth science classes, however it is often taught solely through the discussion of abstract diagrams. Here, we present a laboratory exercise that allows students to explore the greenhouse effect in action and directly relate what they observe back to known theory. In the activity, different "atmospheres" – bags devoid of greenhouse gases versus bags containing 100% greenhouse gases such as methane – are placed over beds of sand, which represent Earth's surface, and are heated via heat lamp. The resulting surface temperatures are then measured to demonstrate the greenhouse effect. This laboratory exercise builds on the CO2-in-a-bottle demonstration, which focuses solely on the temperature of the gases inside the bottle, while our activity mimics the complete greenhouse effect including the impact on Earth's surface temperatures. After completing this activity, students have a more thorough understanding of short- and long-wave radiation and their interactions with greenhouse gases, which can then lead to more detailed discussions about Earth's climate.

Context

Our 100-level introductory atmospheric science course for both majors and non-majors consists of two lectures and one laboratory session each week and covers topics in both weather and climate. This activity is used in the first lab session focusing on climate, after students have been introduced to the greenhouse effect during the previous lecture session. Students gain a hands-on understanding of how greenhouse gases influence Earth's energy budget. This allows us to then continue our discussions of Earth's climate system in more detail, as well as introduce paleoclimate and anthropogenic climate change.

Why It Works

Understanding the greenhouse effect is critical to understanding Earth's climate in the past, present, and future. The greenhouse effect, however, is often taught solely through tedious discussions of short- and long-wave radiation accompanied by a diagram with arrows pointing from the Sun to Earth back to space and back to Earth again. While it is certainly imperative to understand the greenhouse effect conceptually, this activity allows students to bring these diagrams to life. Students come to lab already having this conceptual understanding of the greenhouse effect and then during lab, they can actually explore those processes at work, reinforcing the concepts presented in lecture. This allows a more solid foundation to build upon for discussions about past carbon dioxide concentrations, as well as how changing greenhouse gas concentrations will affect global temperatures in the future.