I take it you do not believe the charts showing an average of 6*C increase in the general Arctic region. Or it could be a lack of study in paleoclimatology in the geologic record.
This will interest you;
"Understanding Time of Observation Bias
Posted on 6 March 2015 by Guest Author
This is a guest post by Zeke Hausfather
Global temperatures are adjusted to account for the effects of station moves, instrument changes, time of observation (TOBs) changes, and other factors (referred to as inhomogenities) that cause localized non-climatic biases in the instrumental record.
While the impact of adjustments that correct for these biases are relatively small globally (and actually reduce the century-scale warming trend once oceans are included) there are certain regions where the impact of adjustments on temperature trends are large. The United States, in particular, has large adjustments to temperature data that have the effect of nearly doubling the warming trend since 1900. The U.S. is somewhat unusual in that most of its historical temperature records were collected by volunteers rather than civil service employees. This has the benefit of giving the U.S. many more records than most other parts of the world, but contributes to the fact that stations in the U.S. tend to have quite a few systemic inhomogenities.
There are two specific changes to the U.S. temperature observation network over the last century that have resulted in systemic cooling biases: time of observation changes at most of the stations from late afternoon to early morning, and a change in most of the instruments from liquid in glass thermometers to MMTS electronic instruments. Back in July I posted a general introduction to U.S. temperature adjustments that looked at the relative effect of each adjustment. Here I will focus in detail on the Time of Observation adjustment, which is responsible for the majority of the change in U.S. temperatures vis-à-vis raw data. In a future post I will address the pairwise homogenization algorithm, which attempts to correct "http://www.skepticalscience.com/underst ... -bias.html