As carbon labeling gets rolling in the U.K., questions abound

Can a bag of potato chips point the way to saving the planet? Some stores in the U.K. are gearing up to “carbon label” their products, aiming to show how much the production, packaging, and transport of consumer goods contribute to climate change. But it’s not a straightforward process: Does the equation stop when the product hits the shelves? What products are most important to label? How do you explain to prospective buyers the meaning of a gram of greenhouse gas? Peter Madden gives the lay of the land, and declares optimism in the face of all the confusion.