"Well, what can you say about the Medieval warm period when the vikings colonized Iceland, Greenland and reached America?! And the drop of the temperatures during the Little Ice Age? The drop was about 4 degrees Centigrade with CO2 levels unchanged."

I don't think the Little Ice Age was 4 C cooler.

Or said differently, if current global temperature were to drop by 1 C for any length of time, I think it's likely that most glaciers would start advancing- or we are about 1 C difference from still being in the Little Ice age.

In time periods of a decade or two, during the Little Ice age, global temperature could been about 3 or possibly as much as 4 C cooler, but if you regard the little Ice as lasting for a few centuries then it's around 1 to 2 C cooler.

I would say the difference between Medieval warm period and today is that Medieval warm period was a much longer warming period. Therefore if our current warming period continues, then possibly within a century or two, we should have a majority of the glaciers which formed during the Little Ice age disappear and Greenland may have more arable land available.