Discussions on global warming often refer to 'global temperature

Yet the concept is thermodynamically as well as mathematically an impossibility

It is impossible to talk about a single temperature for something as complicated as the climate of Earth

the climate is not governed by a single temperature

The Globe consists of a huge number of components which one cannot just add up and average. That would correspond to calculating the average phone number in the phone book. That is meaningless

If, for example,  it is 10 degrees at one point and 40 degrees at another, the average is 25 degrees. But if instead there is 25 degrees both places, the average is still 25 degrees. These two cases would give rise to two entirely different types of climate

the same set of measured data can simultaneously show an upward trend and a downward trend in average temperature. Thus claims of disaster may be a consequence of which averaging method has been used