More than two decades ago, scientists calculated that nuclear war could throw so much debris and smoke into the air that it would block life-giving sunlight from our atmosphere, causing a "nuclear winter." Their eloquent warnings here in Oslo helped galvanize the world's resolve to halt the nuclear arms race.
Now science is warning us that if we do not quickly reduce the global warming pollution that is trapping so much of the heat our planet normally radiates back out of the atmosphere, we are in danger of creating a permanent "carbon summer."
As the American poet Robert Frost wrote, "Some say the world will end in fire; some say in ice." Either, he notes, "would suffice."
But neither need be our fate. It is time to make peace with the planet.
We must quickly mobilize our civilization with the urgency and resolve that has previously been seen only when nations mobilized for war. These prior struggles for survival were won when leaders found words at the 11th hour that released a mighty surge of courage, hope and readiness to sacrifice for a protracted and mortal challenge.
These were not comforting and misleading assurances that the threat was not real or imminent; that it would affect others but not ourselves; that ordinary life might be lived even in the presence of extraordinary threat; that Providence could be trusted to do for us what we would not do for ourselves.
No, these were calls to come to the defense of the common future. They were calls upon the courage, generosity and strength of entire peoples, citizens of every class and condition who were ready to stand against the threat once asked to do so. Our enemies in those times calculated that free people would not rise to the challenge; they were, of course, catastrophically wrong.