Greenhouse gases are gases that exist in our atmosphere that contribute to the overall warming effect known as the greenhouse phenomenon. They include water vapor, carbon dioxide, methane, nitrous oxide, ozone, and industrial gases like hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride.

Scientists say that the chemical bonds in greenhouse gases are not as secure as those of gases that have only two molecules, such as nitrogen and oxygen. Nitrogen and oxygen make up far more of our atmosphere than greenhouse gases. But, because they are comparatively stable when they vibrate, they do not send energy scattering off in all directions. Energy generally just passes on through them.

In contrast, greenhouse gases absorb and emit much more energy. The secret to this capacity lies in their chemical bonds. These gases have more than two atoms… atoms that can move in a variety of ways when they are struck by infrared radiation. The capacity of these atoms to vibrate in different ways makes them much better at absorbing energy than their more securely bonded counterparts with two atoms. These molecules don’t hold the energy forever, though, and so energy is eventually sent scattering off in all directions….including right back to earth.

Frequently Asked Global Change Questions

Greenhouse Gases Absorb Radiation

Water The Greenhouse Gas in a Glass

Movie about the Greenhouse Effect

After working with this animation, students will be able to explain on a molecular level why certain gases are more efficient than others at capturing radiation.

• Recognize and describe the global effects of volcanic eruptions, greenhouse gases, and El Nino. (MD 2.0-E.2b (Grade 8))
• Earth's climate is an example of how complex interactions among systems can result in relatively sudden and significant changes. (NSF 3.8)
• Gases in the atmosphere, such as carbon dioxide and water vapor, temporarily trap infrared radiation from the warmed surface of Earth. The additional warmth in the atmosphere created by the greenhouse effect allows liquid water and other life-supporting processes to exist on much of Earth's surface. (NOAA 3e)

Greenhouse gases; Earth's atmosphere; greenhouse effect; radiation; solar energy; chemical bonds; molecules; atoms

• Chemical Bonding Before students interact with this animation, review the properties of chemical bonding with them. This site provides a good primer on this subject. This virtual chemistry text includes concept maps that can help you construct this experience for students.
• They Look Like... After students interact with this animation, involve them in this design activity: What kinds of models can they construct to show how greenhouse gases behave on a molecular level? Encourage your students to think about materials beyond those found in a science classroom, considering the spine that binds spiral notebooks, for example, and other everyday objects. This movie and its related links might help them explore the possibilities.
• Not all Created Equal After students interact with this animation, involve them in this activity: Greenhouse gases are sometimes rated according to their Global Warming Potential (GWP), which is an estimate of how much they contribute to global warming. In this scale, carbon dioxide is rated as 1. Industrial gases like hydrofluorocarbons have particularly high GWP. Find out more about these gases and their affect on global warming by looking at sites such as this one.