Explanation
Firstly, carbon dioxide builds up in the atmosphere. This is what causes global warming. The carbon dioxide concentration has built up excessively in the past 100 years because more carbon dioxide is being released when fossil fuels are burnt and more trees are being cut down. The trees absorb carbon dioxide and release oxygen so with less trees, less carbon dioxide is being absorbed so remains in the atmosphere. This carbon dioxide rises and becomes part of the greenhouse gases. With more carbon dioxide being released, the greenhouse gas layer become thicker. As you can see, the 'grey' greenhouse gas layer in the second animation is thicker than the greenhouse gas layer in the first animation. The first animation represents the atmosphere 200 years ago and the second animation represents the atmosphere in 2012. |
A thicker greenhouse layer ( animation 2) means that more UV rays and infa-red rays from the sun,reflected by the earth's surface, are being kept inside the atmosphere instead of passing through the atmosphere (animation 1). As more rays from the sun are being kept inside the atmosphere, this
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generally increases the temperature of the atmosphere meaning that the average global temperature increases. There is a lot of evidence to back this thoery up since many scientists have conducted experiments for global warming. Global warming also leads to many other problems including flooding and glacier's melting.
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