If it is such simple science, wouldn't it be trivial to explain the observations that are inconsistent with rising CO2 causing the Earth to warm? Yet we don't find any reasonable explanations for these inconsistencies that would leave the original Hansen hypothesis intact.
What we have recently learned is that temperature rise precedes CO2 concentration rise. Apparently, temperature is the independent variable and CO2 the dependent.
Trying to argue the equivalent of 'chickens can't be the cause of eggs because they have been observed to hatch from them' is not particularly compelling or scientific.