I guess it's like if a study came out and said that drivers of Hummers contribute to global warming 50% more than drivers of Priuses, and 200% more than drivers of Leafs. When considering the footprint of the automobile specifically, that may be correct, but that isn't taking into consideration all the other life style choices which in aggregate, contribute more to a person's overall carbon footprint. Still a 50% reduction in the carbon footprint of your diet is still admirable and a positive thing, I'd say. To me, the bigger issue is that as a consumer, its hard to determine what the carbon footprint of various consumer choices are. It seems like a lot of red tape to require product labeling for carbon footprints like we do for nutrition, but as someone who is concerned about global warming, I'd like the ability to make choices on the consumer level without having to rely on marketers and relatively obscure academic research.