Hamburgers are the Hummers of Food in Global Warming: Scientists (Agence France Presse)

   Simply switching from steak to salad could cut as much carbon as leaving the car at home a couple days a week.

  That's because beef is such an incredibly inefficient food to produce and cows release so much harmful methane into the atmosphere, said Nathan Pelletier of Dalhousie University in Canada.

  Pelletier is one of a growing number of scientists studying the environmental costs of food from field to plate.

  By looking at everything from how much grain a cow eats before it is ready for slaughter to the emissions released by manure, they are getting a clearer idea of the true costs of food.