All I am saying is that quoting some degree number from 1200 years or 12000 years ago is an estimate at best.
Use the very best materials in your mosaic and the result is different if Picasso makes one and Leonardo makes another.
Tree rings go back only 2000 years, much smaller than the ice cores. Ice core reading give you an idea as to the chemical makeup of the atmosphere, maybe dust and pollen count, but where did that material come from?
As I see it, the best indicator as to whether this era seems warmer or colder than another is forensic plant and animal remains.
You go to New Foundland and find the remains of grape vines and you can gather that the climate may have been similar to where grape vines grow today. Putting a temperature number to the climate is imprecise educated guesswork and when we are alarmed at a +/- 1C difference today, that educated guesswork derived number is meaningless.
Ehemm Holden, read up, for there are living trees TODAY that are more than 4000 years old. Close to 5000, with the oldest living one with a root system some 9500 years old, and that one is well in the northern hemisphere....
http://news.nationalgeographic.com/news/2008/04/080414-oldest-tree.htmlTree rings from fossilized trees also exist, all the way to 70 million years ago, as well as leaf and animal fossiles.
I have found some, that are millions of years old and of course show without a doubt a completely different climate.
Tree trunks are also excavated.
Seeds are also sometimes excavated giving an idea of ancient flora. That will tell you where things rank in the Hotter, colder, or roughly equal department.
In my area in the medieval warming period there are claims of barley growing. Only anecdotes so far, however the description of the fields is pretty good. Then barley growing worked no more untill the 20th century, and in the last 10 years it's gone warm enough for wheat and corn.
My point is that biology as a whole tells you a lot about climate, and it's childish to claim that you can trust nothing but the termometer data of recent years (which gets debated here anyway). One has to look at everything, not just this: