More on boring holes.....
As you may recall, Eli got his ears sucked down the Monckton hole with respect to a rather fanciful reconstruction by Shaopeng Huang and friends. What was so strange about this was that the figure the Monckton used, was very different from the 500 year reconstruction published by the gang of Pollack, Huang and Shen in Science 282 (1998) 789 and shown below
Now this reconstruction itself is under discussion, because it falls much lower than most other proxy records. They are also in disagreement with the various bent, broken or distorted hockey sticks which makes them quite popular some places. Mann, Rutherford, Bradley, Hughes and Keimeg took this on in 2003, (for those without access see comments in EOS I and EOS II
The low black line is Huang, et al. (2000) (a slightly updated version from the one shown above) averaging over the northern hemisphere. The dashed one areal weights the borehole data by cos-latitude. MRBHK2003 think that part of the story is that
The overwhelming majority of Northern Hemisphere borehole data come from regions that experience seasonal snow cover. The snow cover partially insulates the ground from cold-season air temperature and fluctuations therein, providing a potential insensitivity of the underlying ground temperature to cold winter air mass outbreaks (and implying a warm-season bias in borehole GST estimates, the degree of which depends on extent and duration of winter snow cover). Little, if any imprint, of the cooling associated with cold air outbreaks is recorded by a ground surface buried beneath a sufficiently thick seasonal snow cover layer. The accumulated influence of such outbreaks on winter mean SAT is considerably greater than the quite modest (on the order of a degree C or less) SAT trends sough from borehole reconstructions. In regions where midwinter snow cover has increased over the past few centuries (which could potentially be associated with either warmer or colder winters, depending on the details of air mass influence in the region), borehole GSTs may therefore exhibit a spurious apparent long-term warming (i.e., colder conditions back in time) due to an increasing incidence of insulating winter snow cover in more recent centuries.Without getting into the who is right who is wrong of this, we recently saw a reference to a new paper Pollack, H.N., Huang, S., Smerdon, J.E., 2006. Five centuries of climate change in Australia: The view from underground. Journal of Quaternary Science, 21 (7): 701-706. Now, if there is one place where it does not snow much, Australia is it. As big as Australia is, even including Tasmania, it goes from ~16 (cos = .96) to ~40 (cos = .77) degrees south, and the difference between the mean latitude and the max/min will only be ~ 10%, so at least two of the issues raised by MRBHK2003 (does that not just roll off the tongue), won't be very much there. Let us go to the video tape then and see how Pollack, Huang and Smerdon do on the MRBHK2003 scale
Follow the bright green line.......hmm. (I know, Australia is not in the northern hemisphere, but look look there is the little ice age. What more do you want from a poor bunny).