Some climate scientists say the world is warming. Some deny that. My question is: How is the world's average temperature calculated?
The average as measured by one temperature measurement station could be the sum of the daily high and the daily low divided by 2. It could be the sum of 24 readings divided by 24. It could be some kind of mean. It could be interpolated from continuous readings.
The average of N stations could be the average of their averages, or it could be some kind of average of cumulative readings across stations.
If stations are dense in some areas and sparse in others, is there any kind of weighting given to more accurately reflect the overall average per unit of area?
Satellites don't have little thermometers attached by long pieces of string, so presumably they measure temperatures through some kind of proxy measurements. What are these? I gather they measure the temperature at different heights in the atmosphere. How are these measures incorporated into global averages measured on the ground?
Once we calculate an overall global average, presumably half the places on earth are colder and half warmer. If the average rises, how does anybody determine which places have warmed, which have cooled, and which have stayed the same?
Finally, climate models attempt to predict future averages. Thus far they haven't proven to be very accurate. How do scientists account for this inaccuracy, and what modifications are they making to their models?
I am a bit of a global warming skeptic, but that has nothing to do with my question. I genuinely don't know how global averages are calculated.