Do you count your carbon?

If you knew a product's carbon footprint, would it influence what you buy? Could carbon-labelling help reduce a country's greenhouse gas emissions?

Tesco and other British high street multiples are introducing carbon labelling on selected products, and the Japanese government recently announced something similar.

But, I'm not convinced that this carbon labelling will work.

First, counting carbon (and the other greenhouse gases) isn't easy: accurate calculations are difficult to come by, and specific to each context (change what you feed the chickens on a particular farm, and the carbon count for the supermarket chicken korma dinner changes dramatically). Then, there is the problem of what to include -- only carbon? Other greenhouse gases? And how do we take account of the 'virtual water' contained in products?

Food product labels are already littered with data (calories, 'nutritional' information, and 'may contain nuts' allergy warnings . . .) and at a time when shoppers are probably most interested in what something costs.

Printing calorie information on food products hasn't exactly stemmed the rise in obesity. And if we can't as a nation manage a lo-cal diet, what chance for a lo-CO2 one? Meanwhile, Tesco has just announced a big drive to introduce yet more cheap ranges of low-cost products. Guess we can say goodbye to the organic aisle.