How true. Common sense is that faculty which tells us the earth is flat.

There is no doubt that the earth has been both colder and warmer and had more or less CO2 over it's lifespan, most of this happened long before the existence of man. The question we now ponder is whether man has caused the most recent spike.

What do you suppose the correct temperature for earth is, and how exactly do we get to that temperature? Surely you will have no trouble answering this simple question with all the evidence you claim to be valid.