The irreversible global catastrophe is imperialist militaries massacring people with little risk to themselves. 
The irreversible global catastrophe is assembly line robots at the Toyota plant becoming sentient and going on a freaking epic terminator style mass shooting and enslave everyone except me 
The most realistic depiction of a superintelligent AI that has ever been written is when VEGA is instructed to start its self-destruct sequence and it helpfully walks you through the process and even gives you strategic tips on how to do it most efficiently.
A computer literally cannot fucking do anything it is not told to do.