18.+What+is+the+atmosphere?19.+How+might+human+beings+be+changing+the+atmosphere?


 * 18 - ****The atmosphere is the blanket of gases which surrounds Earth. It is held near the surface of the planet by Earth's gravitational attraction. **
 * Without the atmosphere there could be no life on Earth **

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19 -**people are changing the Earth’s climate by emitting so-called greenhouse gases to the atmosphere.**

**-The Earth’s climate has always been changing. Only 20,000 years ago, much of Northern Europe was still covered in an enormous glacier that was up to three kilometers thick!**

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