There is not enough "positive feedback" going around in the system to do anything of the sort.

Plenty of feedback mechanisms were proposed, investigated, and found lacking. It's a "makes climate change 10% worse than it would otherwise have been" kind of thing, not a "makes climate change 1000% worse than it would otherwise have been" kind of thing.

Making the temperature rise 10% worse doesn't mean the GDP impact won't be 1000% worse.