Investors who have significant money tied up in the fossil fuel industry — every pension and market fund, essentially — are facing a massive risk. The logic, according to the International Energy Agency (IEA) and banks like HSBC, is this: as the world migrates away from carbon-based fuels, trillions of barrels of oil and billions of tons of coal — the assets sitting on the books of energy companies — will become “stranded,” or worthless.