Greenhouse Gases

Greenhouse gases are: Carbon dioxide, water vapor, methane, nitrous oxide, ozone (occur naturally), CFCs, HFCs, PFCs, sulfur hexafluoride (occur due to human activities). They are gases in the atmosphere, that absorb big amounts of energy, and by this increase the earth's average temperature. They are called greenhouse gases, because they act as a greenhouse. Through them can pass the fast speed rays, but the slow rays are stopped. This is very important, because the most of the sun energy reaching the earth is in fast speed rays. However when it reaches the earth's surface it is changed to slow speed rays, and then is reflected. So when these rays get into the atmosphere they are absorbed, and later are radiated back to the earth. This is a natural process, and due to it the temperature on the earth is not changing greatly. However due some human activities the greenhouse gases in atmosphere have increased, and by this the temperature on the earth has raised.