I think in theory it can be stopped. For example isn't there something like thermonuclear winter that follows nuclear war? I guess from all the dust in the atmosphere reflecting the sunlight?
That is of course not a viable solution, it only shows that apparently man made mechanisms can both heat or cool the atmosphere.
We've never actually created a thermonuclear winter but it was indeed a prediction. I think the problem is one of scale rather than technology ... can we do enough?
True, but I think there was a vulcanic explosion that caused several cold and miserable years? It was too far in our past, though, so again it is part speculation I think. Don't remember the specifics, I think it was during the 30 year war?
... or can we even stop it? As you noted, the earth was cycling through warm and cold periods well before humans could have an effect. Can we stop that if we want to? Or maybe we slow it imperceptibly? I tend to think we need to consider how we'll live "with" global warming. And perhaps how we'll live during the next ice age as well?