3. Handprints, Not Footprints

Jamie Chung for TIME

A bag of chips I bought recently in England had some bad news printed on the back. First, the chips had 14 g of fat. Worse, they had caused 75 g of carbon to be released into the atmosphere.

That bag called my attention to my carbon footprint: those 75 g, added to the 2.3 million from the plane I took there and back, plus the total of all the carbon impacts--the emissions into the air that contribute to global warming--of everything else I do and buy. Footprint math uses life-cycle assessment, or LCA, which calculates the amount of carbon released...