system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's preventing temperature across the globe to reach an equilibrium since air flows freely?

If I open the windows in my room, which has AC turned on and it's cool in the summer, it will quickly become as hot as it is outside, why isn't it happening around the globe?
gpt
We perceive air as this uniform gas that's just everywhere, when in reality air actually clumps around itself and forms bubbles and pockets. These bubbles form when air of the same temperature and density clump together. You'll get bubbles of cold air, bubbles of hot air, bubbles of wet air, bubbles of dry air, etc.

In fact, wind is when these bubbles push against each other. The bubbles are so huge and so sharply determined by their heat and density and humidity, that they don't just blend into each other: they actually form a wall, or a front, and push against each other.

You may have heard the weather forecast talking about a warm front or a cold front coming in. That's a big bubble of one type of air pushing another. You get wind at the line where the bubbles meet, and one bubble is pushing the other.

Some airline turbulence is also caused by these bubbles, since they don't just push around horizontally on the surface of the earth but they stack vertically on top of each other into the stratosphere, too. So sometimes when there's turbulence or the feeling of a sudden drop while flying, it might be because the plane is punching through one air bubble into the next.