It is entirely possible that global warming could tip us into the next ice age, though probably not in our lifetimes.
First you would need a world-wide cloud layer reflecting insolation back without conversion to IR. As the temperature drops, ice forms. When the clouds dissipate, the ice takes over reflecting sunlight out.
Or it could return us back to the hothouse earth of the cretaceous era. Or it could turn our entire planet into a second Venus with a runaway effect from all the methane. Or it could do almost nothing at all. There is just no way to know because it's never really happened before. We are playing with fire for sure.
First you would need a world-wide cloud layer reflecting insolation back without conversion to IR. As the temperature drops, ice forms. When the clouds dissipate, the ice takes over reflecting sunlight out.