Steve McIntyre writes of the curious uptick in the 20th century, which doesn’t seem to be rooted in reality, or to have been in Marcott’s PhD thesis:
While one expects a difference between NHX and SHX in the Holocene, the remarkable difference between NHX and SHX not just in the 20th century, but in the 19th century is a source of considerable interest. According to Marcott, NHX temperatures increased by 1.9 deg C between 1920 and 1940, a surprising result even for the most zealous activists. But for the rest of us, given the apparent resiliency of our species to this fantastic increase over a mere 20 years, it surely must provide a small measure of hope for resiliency in the future.
Read his entire essay here at Climate Audit