[Zon]

What does this mean for the Vostok ice core readings? Are they unreliable or has the methodology been set and therefore must maintain the same methodology when extrapolating into the future? Or am I missing something here?

[ancient_geezer]

A link to a copy of the actual paper discussed in the article, they bring up some very interesting issues concerning even the validity of using a global average to represent a 3 dimensionally dynamic field such as a temperature in an ever changing climate:

Does a Global Temperature Exist
Christopher Essex, Department of Applied Mathematics, University of Western Ontario
Bjarne Andresen, Niels Bohr Institute, University of Copenhagen
Ross McKitrick, Department of Economics, University of Guelph
Journal of Non-Equilibrium Thermodynamics, Volume 32 No. 1

Physical, mathematical and observational grounds are employed to show that there is no physically meaningful global temperature for the Earth in the context of the issue of global warming. While it is always possible to construct statistics for any given set of local temperature data, an infinite range of such statistics is mathematically permissible if physical principles provide no explicit basis for choosing among them. Distinct and equally valid statistical rules can and do show opposite trends when applied to the results of computations from physical models and real data in the atmosphere. A given temperature field can be interpreted as both "warming" and "cooling" simultaneously, making the concept of warming in the context of the issue of global warming physically ill-posed.