Shopping for oatmeal, Helena Bergstrom, 37, admitted that she was flummoxed by the label on the blue box reading, “Climate declared: .87 kg CO2 per kg of product.”

“Right now, I don’t know what this means,” said Ms. Bergstrom, a pharmaceutical company employee.

But if a new experiment here succeeds, she and millions of other Swedes will soon find out. 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.

“We’re the first to do it, and it’s a new way of thinking for us,” said Ulf Bohman, head of the Nutrition Department at the Swedish National Food Administration, which was given the task last year of creating new food guidelines giving equal weight to climate and health. “We’re used to thinking about safety and nutrition as one thing and environmental as another.”