This is a fantastic paper that reconstructs global temerature record without tree ring proxies. it goes back 2000 years.
This paper is important on 2 levels, first, Mann, Jones, Briffa et all use tree ring proxies to recreate historical temperature records that elminate the MWP and create the "Hockey Stick"
Second, this record proves global Warming in the Mideavil period.
http://www.ncasi.org/publications/Detail.aspx?id=3025