In Gil Elliot’s Twentieth Century Book of the Dead, the Scottish writer seeks to estimate how many human beings died as the result of mass violence during the 20th century, concluding that the toll was about 110 million. Even without a nuclear winter, he also estimates that a thermonuclear war between the United States and Russia could have killed two billion, back in 1982.
His conclusions about the ethics of this have relevance to the question of climate change:
The moral significance is inescapable. If morality refers to relations between individuals, or between the individual and society, then there can be no more fundamental moral issue than the continuing survival of individuals and societies. The scale of man-made death is the central moral as well as material fact of our time.
With nuclear weapons and anthropogenic climate change, humanity has engineered two possible calamities, each of which could potentially eliminate the species. The moral obligation to curb both risks is immense, and ought to be a top political priority everywhere.