Has anyone or any research body ever done the calculations to work out
how hot the earth would have to get before a runaway greenhouse effect
kicked off? I don't mean where it rapidly warmed a few degrees then
stopped , I mean a venus style effect with boiled off oceans. Since
some 5 mile wide impacting asteroids with accompanying global
firestorms in the past haven't managed it I doubt we will with too
many 4x4s and coal fired power stations , but I'm just curious as to
what it would take to push the climate so far it never came back.

B2003