Answer:
A greenhouse effect is when a planets atmosphere gets thicker and warms
Explanation:
As a planet with water's parent star gets brighter every million years, The amount of evaporation increases. these are called greenhouse gasses. greenhouse gasses include water vapor and Carbon. This is why Venus is a burning hell. it was once like earth, but the sun kept getting brighter and brighter, causing clouds to form all over the rock, trapping in more heat, and making it far to hot for even metal. One day this will happen to earth, as well. this is why we have global warming. It can be caused by Co2 from earth's inhabitants and water vapor from it's vast oceans.
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