Here's some miscellaneous food stuff (via FCRN) to go in your bags!
Local food doesn't matter: "Total GHG emissions are 8.1 t CO2e/household-yr, meaning delivery accounts for only 4% of total GHG emissions [within] transportation as a whole, which accounts for 11%. Wholesaling and retailing of food account for another 5%, with production of food accounting for the vast majority (83%) of total emissions.
Within food production, which totaled 6.8 t CO2e/household-yr, 3.0 t CO2e(44%) were due to CO2 emissions, with 1.6 t (23%) due to methane, 2.1 t (32%) due to nitrous oxide, and 0.1 t (1%) due to HFCs and other industrial gases. Thus, a majority of food’s climate impact is due to non-CO2 greenhouse gases."
This paper is really interesting -- read it if you are into carbon footprints, local/organic/vegetarian food, etc.
Meanwhile, the UK's Secretary for the Environment talks about food security and production, saying "If we want to encourage more agricultural production, it would help a lot if we stopped getting in the way. Escalating tariffs must be removed across the board in developed and developing countries. And a deal in the Doha negotiations would be the best way of showing that we are serious. Fourth, we cannot simply focus on yields. We need to balance the amount we produce against long-term sustainability of production. So we need to change the way we produce our food."
In "Vulnerability of exporting nations to the development of a carbon label in the United Kingdom" [pdf], the authors worry that labeling will have adverse impacts on poor exporting nations. On the same topic, comes a more-predictable perspective from a Dutch food processing association. Their new report [pdf], "Carbon labelling of food: (how) can the consumer consider climate impact in their food purchases?", will confuse consumers.
Bottom Line: Perhaps you should just ignore all this complicated debate and go buy some stuff... in free bags!