In a lecture, Dr Rowan Williams urged a "radical change of heart" to prevent runaway climate change.
At York Minster he said humanity should turn away from the selfishness and greed that leads it to ignore its interdependence with the natural world.
And God would not guarantee a "happy ending", he warned.
Dr Williams has often spoken out about environmental issues.
Speaking on Wednesday he said just as God gave humans free will to do "immeasurable damage" to themselves as individuals it seemed "clear" they had the same "terrible freedom" as a human race.
"I think that to suggest that God might intervene to protect us from the corporate folly of our practices is as unchristian and unbiblical as to suggest that he protects us from the results of our individual folly or sin," he said. …
Without a change of heart, Dr Williams warned, the world faced a number of "doomsday scenarios" including the "ultimate tragedy" of humanity gradually "choked, drowned, or starved by its own stupidity." …