The ipcc reports vary from TAR, AR4 and AR5. Mostly AR4 and AR5
From observations confirming the poleward advance to the IPCC being clear that a cooling stratosphere causes the circumpolar jets, westerly jets or another common name in the Polar Vortex to tighten.
I have posted that the IPCC also state that like ghg's ozone loss also also contributes to a contraction of the polar vortex.
You can go on a fish hunt if you want to looking up every nook and cranny for a way out of this. But for what I have posted it is clear.
How one could construe anything less would have to be plain mischievous.
you need to address the common theme and that is a cooling stratosphere is responsible for a poleward shift in the polar vortex.
