Vox: The good news is that the world is steadily becoming less and less carbon-intensive. That is, we need to burn fewer fossil fuels to generate a dollar's worth of economic activity. Part of the reason for that is our cars, homes, power plants, and factories are all getting more efficient -- we can do far more with a given amount of coal, oil, or natural gas than we used to.
But here's the bad news: Carbon intensity isn't falling fast enough. Between 2000 and 2013, carbon intensity fell by 0.9 percent...