"Transitions" is way too vague to mean anything. What will "transition"? The climate? Another climate transition on the order of the most recent interglacial be

"Transitions" is way too vague to mean anything. What will "transition"? The climate? Another climate transition on the order of the most recent interglacial beginning seems reasonable (+3-5 C over centuries), but if that's what "critical transition" means, we've been through dozens over the last million years and are none the worse for wear. (At least if you just look at species count.) What would the actual negative consequences of such a transition be? Would they outweigh the positive consequences? Would they outweigh the cost of avoidance measures, taking into account the probability that those avoidance measures won't work? The avoidance measures here are extreme even by extreme standards - we're talking a comparable cost to a global thermonuclear war (large decrease in population, large semi-permanent decrease in global GDP). We need numbers here, guys. Numbers.