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. It's a compelling argument, but only if we can answer a key question.
If you spend time with environmental activists, you'll find that most of us don't fit the stereotype. We won't scold you for driving the wrong car or turning up the heat on a cold day, and we probably tell more jokes about ourselves than any else.
Is 40 miles per gallon (mpg) the new 30? Could this be the de facto standard for a new crop of vigorous, green machines that promise to cart our gracefully aging selves around while taking baby sips of fuel or electrons?