Global warming/Vostok core

About
The Vostok core is an ice sample drilled at in Antarctica in 1996. This core produced a record of past environmental conditions stretching back 420,000 years and covering four previous glacial periods. This was the longest such record available at the time and remained so until the drilling of the core in December 2004, which obtained a record going back 740,000 years and revealing 8 previous glacial cycles.

See for details and interpretations of the available ice core data.