Section 1 responses
ISSUES ARISING ON Para 1.1 OF THE TERMS OF REFERENCE
1. The allegation of ignoring potential problems in deducing palaeotemperatures from tree ring data that might undermine the validity of the so-called “hockey-stick” curve. In the late 20th century, the correlation between the tree ring record and instrumental record of temperature change diverges from that for the earlier period. The cause of this divergence does not appear to be understood. If the method used to deduce temperatures from tree ring proxy metrics for the earlier tree ring record is applied to the late 20th century tree ring series, then declining temperatures would be deduced for the late 20th century. It is alleged that if the cause of divergence between the tree ring and instrumental temperature record is unknown, it may have existed in earlier periods. Therefore if tree rings had similarly failed to reflect the warming of the early Middle Ages, they may significantly under- estimate the warming during the Medieval Warm Period, thus falsely enhancing the contrast between the recent warming and that earlier period. (It is this contrast that has led to statements that the late 20th century warming is unprecedented during at least the last 1000 years.)
Issues associated with Section 1 can get highly technical. Comments regarding general techniques, divergence, the hockey stick can be commented on here but check the specific questions first. Also, each section follows the format shown: A general issue, 1. , has specific questions, Section 1.1, Section 1.2, Section 1.3, Section 1.4, Section 1.5, Section 1.6, Section 1.7, Section 1.8, Section 1.9., for example. Note that the last specific question entry in each section, Section 1.10, Supplemental Questions in this case, is a place to create questions that were not specifically asked but perhaps should be.