What is it about CO2 that makes it a greenhouse gas?
CO2 is not transparent to infra-red. Mostly, the Sun doesn’t heat the atmosphere. Visible light passes through the atmosphere, which is transparent to visible light, and strikes the ground, where it is absorbed. It is then radiated back in the form of infra-red. CO2 is not transparent to infra-red, so the heat generated is caught in the atmosphere. To a certain extent, this is a good thing. It’s cold out there. On the dark side of the Moon, the temperature can drop to -250ºF, while on the dark side of the Earth, it rarely falls below -40ºF, and that’s at the poles. But if the CO2 gets too thick, if the atmosphere contains too much, too much heat will be held, and the atmosphere will begin to heat up.
