Dr. Miller, I presume? Thanks for your technically esteemed statement..... I am sure that you are you aware that 92% of the carbon dioxide produced yearly on the planet is generated by man? A mere 8% are from natural sources...... No wonder the planet is becoming a sauna!.....  Whoops, a typo,..... correction:     8% of the world's production of CO2 is anthropormorphic (man caused) and 92% is from natural sources... what about those isotopes again and what exactly is your point?