DOES CARBON DIOXIDE WARM PLANET EARTH?

1. Does carbon dioxide absorb heat? On what data can your conclusion be based?

2. Does carbon dioxide in the earth's atmosphere contribute to higher global temperatures? On what data can your conclusion be based?

3. What sources might you use to find the best data to answer these questions? What measurements could be used to obtain the answers?

 1. CARBON DIOXIDE ABSORBS HEAT

Why do some molecules absorb heat? Each molecule has a specific shape as the atoms' electrons try to maximize the distance between each other. These atoms can vibrate in their position if packets of energy can be absorbed and each chemical bond is prepared to absorb energy of only certain wavelengths. (The forms of electromagnetic energy, which includes heat, radio waves, light, UV light, and X-rays, differ in the length of their waves.) If you pass infrared energy (heat) through molecules of carbon dioxide, certain wavelengths of this infrared energy are absorbed rather than transmitted (see the chart below). It is observed that carbon dioxide (CO2) can absorb infrared wavelengths of 4 and 15 microns. In other words, carbon dioxide absorbs heat.

chart

2. CARBON DIOXIDE IN THE ATMOSPHERE WARMS THE PLANET

If the temperatures of Venus and the Earth were determined only by their distances from the sun, their average temperatures would be 100oC and -18oC, respectively. Both of these planets possess atmospheres whose molecules absorb heat. Since much of the energy from the sun is retained around the planet instead of radiating into space, the planets are warmer than they otherwise would be. Venus, whose atmosphere is 96% CO2, has an average temp of 450oC. The earth's atmosphere possesses water vapor and CO2 which absorb heat and its average temp is 15oC.

earth absorbing sun's rays

3. SOME GREENHOUSE GASES ABSORB FAR MORE HEAT THAN CARBON DIOXIDE

graph

--after Kemp, 2004

graph

--after Kemp, 2004

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