Agriculture is just one of the sectors in which carbon labelling — the labelling of a product to show how much carbon (and other greenhouse gases) have been emitted during its ‘lifecycle’ — is being used to show how individual products contribute to climate change. The logic behind applying carbon labels to agriculture seems sound enough: agriculture accounts for 10 to 12 per cent of global greenhouse gas emissions and produces much of the food we eat and the products we buy. Finding a way to tell consumers how much individual agricultural products contribute to this should encourage them to choose those products with the lowest carbon footprint and help make agriculture more sustainable. But the truth is that it is very difficult to provide accurate carbon labels for agricultural products. And carbon labelling can impact farmers in the developing world in ways that don’t support development.