Despite all the meetings, promises, and apocalyptic threats, global carbon emissions have risen from the Kyoto Protocol of 1997 until today -- from around 6.5 billion metric tons per year to nearly 10 billion. If both China and the U.S. had tackled this issue back in 2001, perhaps we wouldn't currently be in this pickle. Chalk that up as another opportunity cost (which might just cost us the planet). Instead of haggling over currency, hacking, and sea-lanes, the two superpowers should be thinking big. Between them, the U.S. and China account for nearly one-third of the global economy, nearly one-quarter of the world's population, and more than two-fifths of the world's carbon emissions. What these two countries do by definition has an enormous global impact.