Hi, I'm Steve Jones, and I'm going to explain why the earth's temperature is increasing. The earth of course, is a planet, a fairly average planet, and this is the solid body of the earth, here, and above the earth of course, there is the atmosphere, so this is the atmosphere, which contains oxygen, nitrogen, and so on, and gets thinner and thinner, towards the edge, but one of the gases within the atmosphere, is carbon dioxide, and the carbon dioxide is regulated, the levels of carbon dioxide are regulated by forests, seas, and so on, so carbon in carbon dioxide is locked up in organic material, on the surface of the earth, in trees or in the seas. Now, what has been happening of course, is the trees have been removed, much of the forest have disappeared. What that means is, that the carbon dioxide which previously was absorbed by these trees, is no longer absorbed, so the amount of carbon dioxide in the atmosphere, is increasing. One of the functions of carbon dioxide in the atmosphere, is to absorb radiation coming in, which is very good. One of the problems though, if there's too much, it absorbs too much of this radiation, and radiates out heat radiation, or infrared radiation, and therefore, the whole of the earth, will get warmer, because this balance has been upset. Normally, radiation could escape from the earth, but this band of carbon dioxide, and other greenhouse gases like methane, are causing that material, that energy, to be absorbed within the atmosphere, and to be retained within the atmosphere, so overall, the atmosphere is getting warmer. A run away greenhouse effect, is seen on Venus for example, where the temperature in the atmosphere is hugely higher than it should be, and it is because of this huge effect, greenhouse effect, which we get because of the carbon dioxide, and other greenhouse gases, so that's basically why the earth's temperature is increasing.
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