Multi-gas approaches to climate change policies require a metric establishing equivalences among emissions of various species. Climate scientists and economists have proposed four classes of such metrics and debated their relative merits. We present a unifying framework that clarifies the...

Multi-gas approaches to climate change policies require a metric establishing ?equivalences? among emissions of various species. Climate scientists and economists have proposed four classes of such metrics and debated their relative merits. We present a unifying framework that clarifies the...