A more descriptive term than "global warming" is global climate change. It just so happens that, on average spatially, the "change" is toward warming.
Global climate change... Starts with climate turbulence as masses of warmer air around the world rises. It causes the waves in the jet streams to gyrate more northerly & southerly and along with it more extremes in warm and cold climate both up in Canada and down here in the lower 48.
In addition to understanding that warming causes turbulence in the global atmospheric system, the "on average" thing is critical to understanding why we can have cold weather, particularly snow, at a time of year when it's typically warm.
The best mental picture I have about the concept of "averages" is a joke:
A man is standing with one foot in a bucket of boiling water and the other foot a in bucket of ice water.
The man is asked, "How's the water?" To which he replies,
"On average it's comfortable."
You know the one about statisticians out deer hunting; one shoots and misses to the left. The other shoots and misses to the right, at which point the third guy says, "On Average you Got 'em!"
So now, back to the man with his feet in the buckets. Lets say the boiling water stays boiling, and the ice water melts and warms very slightly... still really cold. On average, the water has warmed, right? If the two buckets represented the Earth, one area hot and one cold, you could still say the "Earth" was, on average, warming, regardless of the extremes.
Now, with the jet stream fluctuating, those "extremes" move around, making it a little more complicated than a couple of buckets. It's just a little more complicated than the small minds on Fox News Corporation seem to be able to comprehend... either that, or they have ulterior motives for misleading the public.
