China is at once the world’s largest carbon-dioxide emitter, largest coal burner, largest manufacturer of solar panels and wind turbines, and largest consumer of solar and wind power. It is both the world’s most pressing clean-energy problem and its most promising clean-energy solution. More than any other country, it is where the global fight against climate change will be won or lost. Hundreds of billions of dollars in public and private capital are being spent in China to scale up cleaner forms of energy. But, in fundamental ways, that money is being spent inefficiently. And that is a threat to global efforts to address climate change.