It is not CO2 alone, it is any warming, we have a water cycle that is why, any increase in heat causes an increase in evaporation and clouds, the atmospheric convection speeds up and warmth is delivered north and south of the poles via the Hadley cells and other circulations.

Because of this ocean surface temperatures never exceed 31C which keeps the tropics relatively cool and warms the polar regions, this has happened before many times during warming, even before CO2 was a factor.

There's more ice at Antarctica then ever measured in history today, and the ice at the north pole is greater today than just 2 years ago. Clearly co2 has no effect on the poles.

Carbon dioxide causes the earth to retain heat by sort of trapping and absorbing the sun light rays that would otherwise be reflected back into space by earth's surface. Sun light has to travel a longer distance through the atmosphere when it enters near the poles because it is not coming in with a smaller degree, not like it strikes the earth with 90 degrees at the equator. So it meets more carbon dioxide molecules.

Because that's where the ice and snow is.

polar amplification is covered in this link

http://www.realclimate.org/index.php/arc...