Readers comments on the six questions below:
“2) What is the ideal atmospheric CO2 concentration?”
This is a key question which I have been asking for many years now. There are enormous benefits to high CO2 concentrations and I am not aware of any consensus on the question of what would constitute ideal levels.
A case can be made to say that the pre-industrial Pleistocene CO2 concentration of ~280 ppm (falling below ~200 ppm during glacial periods) was close to becoming dangerously low. The oceans have always been sequestering CO2 from the atmosphere — slowly but surely. The trend has been to ever lower levels — from 3-5 million ppm (measured in current atmospheric density) 4 billion years ago, down to ~7000 ppm 300-500 million years ago when life flourished both in water and on land, down to ~280 ppm a century and a half ago. Doubling, tripling, or even quadrupling this level is nothing to be frightened at — the planet thrived at even much higher levels.
Another adds a question of his own:
7) What precisely does “global average temperature” mean? What data does one gather, and what formula does one use, to compute it?
If I asked for a method to compute “the average color of the earth,” 20 scientifically knowledgeable people would imagine 20 different interpretations of the phrase, each with wildly differing methods for gathering and combining the data. The “global average temperature” is a similarly nebulous concept.
It’s not that these concepts don’t have meaning – just that they are inherently slippery enough that one is free to select whatever interpretation of the phrase most encourages the desired conclusion.