The last decade has seen an extraordinary shift in expectations for the world energy system. After a long era of excess capacity, since 2001, prices for oil and most energy commodities have risen sharply and become more volatile. Easy-to-tap local fuel supplies have run short, forcing major energy consumers to depend on longer and seemingly more fragile supply chains. Prices have yo-yoed over the last 18 months: first reaching all-time highs, then dropping by two-thirds, and after that rising back up to surprisingly high levels given the continuing weakness of the global economy. The troubles extend far beyond oil. Governments in regions such as Europe worry about insecure supplies of natural gas. India, among others, is poised to depend he...