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 
I remember reading one of those Less Wrong-ite "dangers of AI" stories where it's mentioned that nobody can stop the AI superintelligence because it keeps its servers and cores dozens of kilometers underground.
Dozens of kilometers.
Underground.
Evidently the author had never heard of the geothermal gradient. Server racks generate so much waste heat that they have to be put in rooms specifically designed to maintain high airflow to keep the entire room from cooking. Imagine trying to keep that shit cooled when it's so far underground that the ambient temperatures melt lead, to say nothing of how much work it would be to actually excavate all that. The Kola Borehole only goes 12km down and that took decades to dig.
On the cryogenic moon Titan
This is such a perfect encapsulation of the techbro desire to speak authoritatively about subjects they know nothing about
That is like half the people I meet in this wretched country. No intelectual curiosity, just smugly talking down to everyone about something they know nothing about.
What you don’t know is that the earth is just a giant computer chip. We’ve been played all along. The robots are already in our soil