The carbon cost of breakfast at COP26

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A French minister told people to eat fewer croissants at this year’s COP26 summit, after the menu said the carbon cost of the pastry was higher than that of a bacon roll, even if it was made without butter. Tim Harford investigates whether this claim could be true, and how the effect of food on climate change can be measured. (Photo: Continental breakfast with coffee and croissants: Cris Cantón/Getty Images)