Abstract

I will explain why the traditional approach to framing climate change policy in terms of long-term stabilization targets for atmospheric concentrations of greenhouse gases gives rise to some rather ill-posed scientific questions. Moving on from this, I will explain how focusing on cumulative emissions of the longest-lived greenhouse gases provides a scientifically more robust basis for policy. Acknowledging the existence of an uncertain limit on the total amount of carbon dioxide we can release into the atmosphere draws attention to the possibility that we will find out, too late, that we have released too much. Under those circumstances, the only way left of avoiding dangerous climate change would be artificial draw-down of atmospheric carbon dioxide or other, even more speculative, forms of geo-engineering, hazards of which I will discuss. Finally, I will speculate on how a cap on cumulative carbon dioxide emissions might translate into an effective mitigation policy.