I have been reading through KBCD III/3 which is his doctrine of Creation. This particular section is about the Providence of God. Briefly, Barth sees this as being intertwined in the covenant that God made with humanity. God, will preserve us and take care of us.
“The creature has to be preserved, and in fact preserved, because this particular will of God has to be done, and is in fact done, both in heaven and on earth, because Jesus Christ is at the right hand of the Father and is our advocate”. KBCD III/3 p.58
“It is the love of God which preserves the creature.” KBCD III/3 p.59
It is this belief of Barth that will protect us and care for us that seems to have kept us from nuclear war and will keep us from this outcome. http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-1.html