That honestly doesn't make any sense to me. How could heat pass through a gas one way but not the other? Its not like our upper atmostphere has a bunch of doors that can only open one way. To me, that seems to fly in the face of everything I've been taught about how the physical universe works.
If heat can pass through a substance one way, there's no reason why it can't go through the other way. Except for 'greenhouse gases' apparently.
The closest thing I know of that works this way is one-way mirrors. But that doesn't have the same effect. The reason you can see through one side and not the other is because most light is reflected, but not all. Thus if you're in a dark room, the light coming in from the outside will overwhelm what little light is being reflected from within the room. But if you're on the outside, virtually no light is coming through from the dark side and thus you can only see what is being reflected.
In short, it makes no sense to me and flies in the face of everything I've been taught. Now, I'm not a climate change denier. Actually, this is something I just now thought about. I've never really bothered to question it before.