[cogitator]

If the hockey stick theory is so accurate, what made the glaciers disappear over the great lakes region and Canada over the last 20,000 years?

Glacial/interglacial changes are primarily driven by Milankovitch cycle forcing. Milankovitch cycles change the total amount of solar insolation the Earth receives. When the cycles positively or negatively reinforce each other, there are significant maxima and minima in solar insolation. These maxima and minima mark the glacial/interglacial transitions. The changes driven by solar insolation are reinforced by a positive or negative global temperature feedback driven by atmospheric CO2 concentrations.

Now aren't you glad you asked? If you want to check and see if my basic description above is accurate, use Google.

[Always Right]

The changes driven by solar insolation are reinforced by a positive or negative global temperature feedback driven by atmospheric CO2 concentrations.

Pure speculation. There is nothing that supports that.