Martin Heller is one of those people. He’s an engineer at the University of Michigan’s Center for Sustainable Systems and one of several researchers who published a paper in Environmental Research Letters assessing how much variability there is in the greenhouse gas emissions of American diets. And it turns out the answer is: a lot. Forty six percent of the total emissions from food came from the diets of just one-fifth of the population. Mostly that’s because those people eat a lot more meat than the others, especially methane-spewing beef. Animal protein jacks up the emissions for the top consumers,...