Climate plays a very important role in the life of plants, animals and humans, and is dif-
ferent in different parts of the world. Some
scientists think that the world is becoming
hotter. Winters have become warmer be-
cause of the greenhouse gas. During the
last 100 years people have produced a lot
of CO2 gas. This gas in the air works like
glass in a greenhouse. It lets heat get in, but
it does not let much heat get out. So the air
becomes warmer. Where does the CO2 gas
come from? CO2 gas is mostly produced by
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