Imagine you’re inside a greenhouse, surrounded by plants. Sunlight streams in through clear glass walls. The glass traps the energy of the sun in the form of heat, warming up the air, water, and surfaces around you. Simple enough, right?
It turns out the Earth’s atmosphere works in a similar way. Sunlight travels through the atmosphere and hits the ground, warming it up. Some of the heat that’s in the ground stays there, but some of it shoots back upward, through the atmosphere. But remember how the glass walls of a greenhouse trap in heat? It turns out that certain gases, including carbon dioxide, do the same thing. When heat tries to pass through them, they capture it and reflect it back toward the Earth for a second time. The more of those gases that are in the atmosphere, the more heat they reflect back, and the hotter the Earth becomes.
This process explains why the amount of carbon dioxide in the air has been so closely tied with how hot the Earth has been over time. And the similarity between this process and the way that greenhouses work has earned it the name “the greenhouse effect”, as well as the name “greenhouse gas” for the types of gas that cause it.
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