In most "long" presentations of climate change in the IPCC framework, we see Vostok ice core going back to about 800 Kyr, covering most of the Pleistocene. What easily gets lost sight of in this format is just how unusual the Pleistocene itself is. It is one of only a few glaciations in the entire history of the earth. There have been some interesting recent discoveries in the Pliocene – the geological period just before the Pleistocene. Here is some information on an interesting Pliocene wood sample collected in 1997 from north Greenland (c. 80°31.9″ⱎ, 65°25″ⱗ, 70 m).
Here is a picture of the Pliocene wood sample:
Ole Bennike reported here:
it is obvious that the trees grew locally, since leaves, needles, seeds and cones are common, and the rich fossil insect fauna also comprises numerous species that are dependent on trees (BàÆàⵣher 1995)….Of the tree trunks from the Kap KàÆàⷢenhavn Formation, only a few measured more than 10 cm in diameter, and the largest sample had a diameter of 18 cm. The lack of pines in the Kap KàÆàⷢenhavn Formation distinguishes that flora from most Late Cenozoic floras from northern Canada.
He compared the site to northern Canadian sites as follows:
From the Worth Point Formation on Banks Island trunks of Larix up to 26 cm in diameter have been reported. Laric laricina is the only conifer reported from the Worth Point Formation; this sequence is considered to be around 1.5 Ma old (Matthews & Ovenden 1990). The floristic composition and the size of the wood fragments from Washington Land bear strongest resemblance to that of the Beaufort Formation on Meighen Island and the high-level alluvium on Ellesmere Island, for which a Mid or Late Pliocene age is suggested, perhaps around 3 Ma.
These larix stumps appear to be comparable in size to those at the Polar Urals site (where the cutoff for modern sampling was about 10 cm). North Greenland in the Pliocene was tectonically almost exactly where it is now, but Arctic climate was not simply warmer than today, but a lot warmer. The Miocene was even warmer. On this scale, Milankowitch factors would not be anything other than a modulating factor. The placement of the start of the cooling into the Pleistocene is about 1.4-1.5 Ma.
I’ve noticed some other interesting Pliocene references, which I’ll post up from time to time.
Ole Bennike Late Cenozoic wood from Washington Land, North Greenland. Downlaoded from http://www.geus.dk/publications/review-greenland-97/gsb180p155-158.pdf