Power shortages are turning out streetlights and shutting down factories in China. The poor in Brazil are choosing between paying for food or electricity. German corn and wheat farmers can't find fertilizer, made using natural gas. And fears are rising that Europe will have to ration electricity if it's a cold winter.

The world is gripped by an energy crunch — a fierce squeeze on some of the key markets for natural gas, oil and other fuels that keep the global economy running and the lights and heat on in homes. Heading into winter, that has meant higher utility bills, more expensive products...