Economist: CALIFORNIA tried to save the world again this week. Arnold Schwarzenegger, the state’s governor, rounded up politicians and officials from across the globe (expending quite a bit of carbon) and urged them to tackle climate change more aggressively. To set an example, he ordered state power companies to obtain one-third of their electricity from renewable sources by 2020. California is indeed leading the way in cutting greenhouse-gas emissions–but not for the reason it might want. Mr …