New labels listing the carbon dioxide emissions associated with the production of foods, from whole wheat pasta to fast food burgers, are appearing on some grocery items and restaurant menus around the country. - People who live to eat might dismiss this as silly. - But changing one’s diet can be as effective in reducing emissions of climate-changing gases as changing the car one drives or doing away with the clothes dryer, scientific experts say. - If the new food guidelines were religiously heeded, some experts say, Sweden could cut its emissions from food production by 20 to 50 percent. -- An estimated 25 percent of the emissions produced by people in industrialized nations can be traced to the food they eat, according to recent research here. And foods vary enormously in the emissions released in their production. -- While today’s American or European shoppers may be well versed in checking for nutrients, calories or fat content, they often have little idea of whether eating tomatoes, chicken or rice is good or bad for the climate. - Complicating matters, the emissions impact of, say, a carrot, can vary by a factor of 10, depending how and where it is grown. - Earlier studies of food emissions focused on the high environmental costs of transporting food and raising cattle. But more nuanced research shows that the emissions depend on many factors; including the type of soil used to grow the food and whether a dairy farmer uses local rapeseed or imported soy for cattle feed. Business groups, farming cooperatives and organic labeling programs as well as the government have gamely come up with coordinated ways to identify food choices.