I’m not a big fan of carbon labels, or other sustainability labels, for that matter. At first glance, they seem very appealing, and in a perfect world they could perhaps be very helpful. But in reality, with the vast amount of information that they attempt to distill, and the high degree of uncertainty about the underlying data, I am not sure they are very accurate. Perhaps even more importantly, I feel uncomfortable about the social behavior they induce. From my own experience, and after speaking with others, I think they create stress for individual shoppers. I also think they mislead people into thinking they are making a positive difference whereas at best they are likely choosing between less bad options. See my short comment on this topic at Nature Climate Change.