Human-generated greenhouse gas emissions imperil a global resource: a biosphere capable of supporting life as we know it. What is the fair way to share this scarce resource across present and future generations, and across regions of the world? This study offers a new perspective based on the guiding ethics of sustainability and egalitarianism.

Sustainability is understood as a pattern of economic activity over time that sustains a given rate of growth of human welfare indefinitely. To achieve this, the atmospheric concentration of carbon must be capped at some level not much higher...