Think it's hot now?—Just wait. There's a lot we don't know yet about global warming and the greenhouse effect, but we also understand a great deal. What is the greenhouse effect? Everyone has heard the term; few understand it.
First, you need to know that radiation varies greatly in frequency, and the transparency of a substance depends in part on that frequency. Think of X-rays, which pass easily through objects that block visible light.
You're well aware that it's a lot hotter inside a greenhouse than out. This is because incoming radiation from the sun can pass easily through the glass, but much is absorbed by things inside. These items then re-emit radiation at a lower frequency—as heat. The glass, fully transparent to visible light, blocks much of the heat radiation, trapping it inside.
So-called greenhouse gases, such as carbon dioxide, act like glass.
Incoming radiation from the sun passes through the gases easily, but passage of heat
re-emitted from the earth's surface is impeded. We add constantly to the carbon
dioxide of the atmosphere by burning fossil fuels—and thus global warming.
Listen to the Audio (mp3
format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
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Today links to websites on climatic change.