This link - "save the planet, time to eat dog" underlines, in a roundabout way, the importance of a price on carbon rather than cheap theatrics like "food miles" which actually have more to do with protectionism than any actual contribution to saving the planet from too much carbon. Strange though it may seem, sending food half way round the world by sea is very carbon efficient. Cooking it in a pot without a lid is very carbon inefficient. So the truly efficient application of "think globally, act locally" is to put the lid on the pot and stop worrying about where the food was grown.
Likewise with other actions. I drive a 3 litre v6 petrol car. I love it - apart from the fact iit breaks down all the time, and every part is handmade by some cheese-eating surrender monkey half a world away - and at vast expense. I get peeved every time I drive past the specially reserved 'green' carparks in the downtown car-park in Auckland. How do they know how green I am? You see, because I don't have a dog, and because I have my own compost heap, and because I have 900 sq metres of lush green forest on my section, and I am not overweight,I have probably got a much lower green footprint than half the Hybrid driving gits that get the 'green parks'.
However, I don't know, and I don't want to know - all I want is a price for carbon, and then I can let them make the choices they want, and I can make the choices I want, and between us we will optimise our carbon position and pay the right price for it. Then there will be no need for all this silly 'holier than thou' stuff.