"...In all my years of examining economic and environmental trends, I’ve never seen anything like this. Gasoline consumption might shift by a few percentage points per year at most. Coal consumption trends had been very much of that ilk: consumption would shift slowly, but with a long-term trend towards steady growth. "So a drop of this magnitude is a proverbial “black swan“—an unforeseeable event with dramatic, world-changing consequences."As he notes, it's a major reason for the 20-year low in US CO2 emissions, and why the coal companies want to export through the Pacific Northwest.