Many scientists believe the "greenhouse effect" is a poorly-named phenomenon. Most people immediately think of a greenhouse as a place that warms trapped air, much like a car in the sun heats up when its windows are closed. This is not the case with our atmosphere, which is a porous layer through which electromagnetic radiation, both short wave, visible (and ultraviolet) light energy and longer wave, infrared energy, travel.

Visible light, as well as ultraviolet light, travels from the Sun to the Earth. Some of this energy (about 1/3) is reflected back to space by the upper atmosphere, but most of the rest travels unimpeded to the surface of the earth where it is absorbed, The earth radiates infrared energy out into space. However, some of this energy gets "captured" by a layer of GHG (greenhouse gases) as it leaves Earth. Some of the energy captured by these little critters is sent back into space; but some of it gets deflected back to Earth. The rest is absorbed by other CO₂ (or other GHG) molecules. and the process is repeated.

Even though it's an inaccurate metaphor, the name "greenhouse" effect still persists. And the gases that are part of our atmosphere are sorted out according to the way they redirect energy or let it pass through. Greenhouse gases - carbon dioxide, water vapour, and methane - are champs at capturing the heat energy and redirecting it everywhere, including back towards Earth.

The "greenhouse" effect is crucial for all life on this planet. If none of the heat energy were redirected toward Earth, our temperatures would plummet precipitously. But there is sometimes too much of a good thing.

What is Global Warming?

Bad Greenhouse

The Greenhouse Effect

What kinds of radiation pass through the atmosphere, and what kinds are absorbed?

What is the Greenhouse Effect?

Movie about the Greenhouse Effect

After working with this interactive, students will be able to describe the relationship between CO₂ levels in the atmosphere and the temperature of the earth

• Recognize and describe the global effects of volcanic eruptions, greenhouse gases, and El Nino. (MD 2.0-E.2.b (Grade 8))
• Identify and describe a range of local issues that have an impact on people in other places. (MD 6.0-B. 1a (Grade 6,7,8))
• All Earth processes are the result of energy flowing and mass cycling within and between Earth's systems. (NSF 3.2)
• Earth's systems are dynamic; they continually react to changing influences.(NSF 3.6)
• 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)
• Earth's climate is remarkably sensitive to changes in the planet's energy balance (NOAA 3g)
• Relatively small increases in amounts of greenhouse gases-such as carbon dioxide, methane, nitrous oxides and some refrigerants-can magnify the greenhouse effect. (NOAA 4g)
• Interactions between components of the Earth's climate system result in changes to the system and produce emergent phenomena unique to the system. Human beings are an integral part of Earth's climate system. Human activities such as fossil fuel burning or deforestation can affect climate and alter the equilibrium of the climate system. (NOAA, 4h)

Greenhouse gases; Earth's atmosphere; greenhouse effect; radiation; solar energy

• GHG Before students experience this interactive, involve them in this discussion: Where do greenhouse gases come from anyway? This site will help you track down sources for the four primary GHG (greenhouse gases): carbon dioxide, methane, nitrous oxide, and fluorinated gases. (Hint: look under "Greenhouse Gas Overview" section)
• An Appropriate Metaphor After students experience this interactive, involve them in this discussion: Many scientists agree that the metaphor of a greenhouse isn't as scientifically accurate as it could be. Given that, what kind of metaphor or metaphorical term would you use to describe the phenomenon of so-called greenhouse gases directing some energy from Earth back onto its surface? Hint: Using the metaphor of a blanket has also been dismissed. You can find more information about the greenhouse effect here.
• Changes After students experience this interactive, involve them in this discussion: Aside from greenhouse gases, what other natural elements affect the Earth's temperature? Think about factors such as cloud cover and albedo. Need clues? This site will help you get started.