It's not what the OP was talking about, but I'll expand on what you said.
The polar jet stream is driven by the temperature difference between the poles and the mid-latitudes.
Global warming warms the poles more.
The decreases the temperature difference between the poles and the mid-latitudes.
That slows down the polar jet stream.
That makes the polar jet stream meander more, like a slow river.
That brings down pockets of cold air.
Overall, winters will be much warmer (as this one has been), but there will be brief bouts of sudden cold, when the weak polar jet stream lets a polar vortex drop down. That will be accompanied by unusually warm temps somewhere in the polar region, since cold air masses has a finite size. When cold air moves down from the poles, warm air moves up to the poles from somewhere else to replace it.