Carbon emissions in Walkers Crisps

Had a pack of Walkers Crisps at lunch, and noticed on the back it says "75g of Carbon emissions calculated per pack". And this is on a standard packet of 34.5g crisps.

While I admire Walkers for their transparency when it comes to the carbon emissions I can't help but wonder what they're expecting their customers to do with the information. Am I more likely to buy a snack that has a lower "carbon footprint" than another? Well, probably not, but maybe. I suspect we like to think we buy food based on things like taste and nutritional content, but like it on not we are all swayed by things like packaging and the perceived image of the product.

So now along with checking how much fat, salt, sugar and calories are in our food, must we now check the carbon emissions too?

And if I do stop buying food that has high carbon emissions, is it going to make any difference? The food has already been manufactured by that point--any damage already done. It would take a lot of customers turning away from high carbon foods to make a manufacturer modify their process to reduce their emissions, and I doubt enough people care to make that happen.