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Without any CO2 in the atmosphere, the Earth would be a frozen planet.

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CO2 molecules can reflect heat.

Image by UCAR | visit website for more information

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This creates a warming blanket around Earth (greenhouse effect).

Now that we know how CO2 levels influence temperature, let's take another look at our graph.

Place the temperatures at the right CO2 level

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Source: NASA and this really cool graphic

Our average temperature today is also 14°C. Making it four degrees colder doesn't seem like a big deal.


But 4 degrees is the difference between a very pleasant Berlin and a Berlin at the edge of a monstrous glacier that covered a third of Europe.

More info

This is definitely not completely accurate. The ice is a picture of the Perito Moreno glacier in Argentina. I've done my best to scale it: The Reichstag building is 48 m high, the highest columns of the glacier about 70 m. The real glacier would probably be less steep at its end.

A map of the last ice age from Wikipedia:

A very cool picture by Randall Munroe at

Source of Ice age maps | Photo glacier by Time Travel Turtle

So... how do our human CO2 emissions impact temperatures?