If not us, who? If not now, when? As the much-depleted United Nations meets in Canberra, the scale of the global catastrophe becomes clear. The tsunami left Brisbane a flooded ruin. Vanuatu has disappeared. The Madagascan evacuation has failed. Vancouver has been reduced to a radioactive crater. For as far west as Mozambique, as far to the east as Chile, and as far north as Canada, the world is a catalogue of devastation. From the Atlantic,...