Can you put a price on pollution? Some of the world's biggest economies are doing just that as they wrestle with how to make good on grand pledges to tame planet-warming emissions.
Matters are coming to a head.
China, Japan and South Korea have all followed the European Union in pledging to cut emissions to "net zero" in recent weeks, where they release only as much as they remove from the air. U.S. President-elect Joe Biden made the same promise in his election campaign.