The way you were able to put it so simply makes me really wish that explanation was correct, but unfortunately it is not.
It’s more along the lines of:
- All things shine away their hot, as long as they are at least a little bit hot.
- You know the sun shines, but actually the earth shines too.
- Actually, you shine too. (That’s why you can be seen on an infrared camera.)
- The hotter a thing is, the harder it shines.
- The sun is really hot so it shines really hard.
- The earth is much less hot, and shines way, way less.
- The earth gets more hot from catching the shine from the sun, and less hot from shining itself.
- When the hot coming in from the sunshine is the same as the hot going out from the earthshine, the earth says the same hot.
- When the hot coming in from the sunshine is more than the hot going out from the earthshine, the earth gets more hot.
- And as the earth gets more hot, its earthshine becomes harder, until it’s the same as the sunshine again.
- For the earthshine to take the hot away from the earth, it has to actually get to space.
- Otherwise it’s like the earth shines on its own air, and the hot remains basically on (or around) the earth.
- CO2 stops some parts of the earthshine from reaching space.
- This part of the earthshine, when it starts from the ground, basically never gets to space.
- It can only get to space from really high up, where there is not so much CO2 in the way.
- But really high up is also colder, so the earthshine is less (because hotter things shine harder).
- The more CO2 there is, the higher up we have to go, the colder it is there, the weaker that part of the earthshine is.
- And when the earthshine gets weaker, the actual earth has to be hotter to shine out as much hot as is coming in from the sunshine. Which is why CO2 makes the earth more hot.
That’s the point, CO2 doesn’t store energy (well, it does a little, but not so much that it makes any difference). What it does is blocks the energy from leaving (until you reach a high altitude).