The concept of a global average temperature is an interesting one, but the problem with it is that is gives no useful information. It is composed of the average of a certain number of sites, but it doesn’t tell you specifically where or when any changes occurred.
Global average temperatures can be compared to grade point averages. If one’s GPA is at an extreme, such as 4.0 or 0.0, then information can be clearly gained from the number. That person is either doing well at everything or poorly at everything. Similarly, if the global average temperature of a planet is at an extreme, such as above 100 degrees C or below -100 degrees C, then we have useful information: we know we can’t live there without special equipment.
If a person’s GPA goes from 2.5 to 2.6, there is no actionable information unless that person is taking only one class. If the person is taking more than one class, in which class or classes has that person improved, and in which does he or she still need improvement?
Likewise, knowing that the global average temperature has gone up by one degree is equally useless information. Did the entire world get hotter? Did one hemisphere go up by 2 degrees and the other remain the same? Did one fourth of the world get hotter by five degrees and the rest cooler by a third of a degree? Did the temperature increase occur over land or over the oceans? Did it occur primarily at night, or during the day? Or only during the winter, or only during the summer, or both?
On a planet where the extremes of temperature are greater than 100 degrees C apart, where the difference between daytime highs and nighttime lows is routinely greater than 10 degrees C, and where a one degree change falls within the range of natural variation, does a one degree change even matter?