"no more scientific than a monkey with a dart board"
That is really un-fair to the people building super computers to calculate trillions of volumetric elements with hundreds of variables.
The general math has been known since 1896. And even those original gross calculations have turned out to be surprising close.
Current models are just continuing to dial in, refine. Where are these giant errors you speak off?
"In 1896 Svante Arrhenius calculated the effect of a doubling atmospheric carbon dioxide to be an increase in surface temperatures of 5–6 degrees Celsius. This 1902 article attributes to Svante Arrhenius a theory that coal combustion could eventually lead to human extinction."
Even oil company models from the 1970-80's (before they were denying it), have turned out to be correct.
We've known the science for these calculations for over a 100 years.
But yeah, I guess I'm being pulled into responding to an anti-science bot again.