The Global Mean Temperature Anomaly Record
The idea that there is an mean global temperature that can be measured and reported as if it represented a meaningful measure of temperature changes is misleading.
From the study:
At the center of most discussions of global warming is the record of the global mean surface temperature anomaly—often somewhat misleadingly referred to as the global mean temperature record:
[T]his record is only one link in a fairly long chain of inference leading to the claimed need for worldwide reduction in CO2 emissions ... [and] he record is misleading.
This is because the record is often treated as a kind of single, direct instrumental measurement, however, it is really the average of widely scattered station data, where the actual data points are almost evenly spread between large positive and negative values. The average is simply the small difference of these positive and negative excursions, with the usual problem associated with small diff erences of large numbers: at least thus far, the one degree Celsius increase in the global mean since 1900 is swamped by the normal variations at individual stations, and so bears little relation to what is actually going on at a particular one.