Effect of Carbon Dioxide Climate The earth receives a tremendous quantity of radiant energy from the sun, about 30% of which os reflected into space by the earth's atmosphere. The remaining energy passes through the atmosphere to the eatth's surface. Some of this energy is absorbed by plants to drive photosynthesis and some by the oceans to evaporate water, but most of it is absorbed by soil, rock, and water, resulting in an increase in the temperature of the earth's surface. This energy is in turn radiated from the heated surface mainly as infrared radiation, often called heat radiation. The atmosphere, like window glass, is transparent to visible light but dose not allow all the infrared radiation to pass through. Molecules in the atmosphere, principally H2O and CO2, strongly absorb infrared radiation, trapping it in the earth's atmosphere, as show in Fig.9.91. A net amount of thermal energy is thus retained by the earth's atmosphere, which causes the earth to be much warmer than it would be without its atmosphere. In a way the atmosphere acts like the glass of a greenhouse, which is transparent to visible light but absorbs infrared radiation, thus raising the temperature inside the building. This greenhouse effect is seen even more spectacularly on Venus, where the dense atmosphere is mainly responsible for the high surface temperature of that planet. --

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