Hat tip to Hans von Storch for pointing out this comment in the emails. It was sent by paleoclimatologist Ed Cook to the CRU's Keith Briffa, outlining his opinions on the current (2003) state of knowledge of past temperatures:
The results of this study will show that we can probably say a fair bit about <100 year extra-tropical NH temperature variability (at least as far as we believe the proxy estimates), but honestly know fuck-all about what the >100 year variability was like with any certainty (i.e. we know with certainty that we know fuck-all).
Read that carefully people. We know a fair bit about the temperatures in the last 100 years, but only for the extra-tropics. Before that, we know nothing. Nothing.
Read the whole email. It's astonishing.
Aidey in the comments points out that I've got the nuance of this post wrong. What Aidey points out is that what Cook is saying is that we understand short-term variability (<100 years) but not long-term (>100years). What does this mean about our understanding of the much-disputed medieval warm period though?