[Aubs]

It appears to be standard Ice Core Data. http://home.iprimus.com.au/nielsens/medieval.html
It looks very similar to the graph I really wanted.

Here's another, showing 450 KYA. You can't go back too much farther than this because the continents were too far from their current positions to draw scientifically accurate conclusions.

Source: http://images.google.com/imgres?imgurl=http://cdiac.ornl.gov/trends/temp/vostok/graphics/tempplot5.gif&imgrefurl=http://cdiac.ornl.gov/trends/temp/vostok/jouz_tem.htm&h=475&w=570&sz=10&hl=en&sig2=cqvIN9e9 Mq4MARaNjGlQjQ&start=16&tbnid=J0eJqGyxxyIGfM:&tbnh =112&tbnw=134&ei=6m_nRLzsHsSE6AGFtfypDg&prev=/images%3Fq%3Dhistorical%2Bglobal%2Btemperature%26s vnum%3D10%26hl%3Den%26lr%3D%26safe%3Doff%26rls%3DG GLR,GGLR:2006-18,GGLR:en