Tipping point has tipped?
The one I remember scaring the hell out of everyone is the permafrost melt.
Thaw out enough permafrost and it releases enough greenhouse gasses to self perpetuate. No human interaction required.
https://www.space.com/methane-beneath-arctic-permafrost-climate-feedback-loop
Snowpiercer is the sequel to Willie Wonka and the Chocolate Factory.
https://nerdist.com/article/willy-wonka-chocolate-factory-snowpiercer-sequel-fan-theory-dan-cave/