Carbon dioxide, methane, and nitrous oxide together cause the vast majority of global warming. Producing a little more than 2 pounds of beef causes more greenhouse-gas emissions than driving a car for three hours and uses up more energy than leaving your house lights on for the same period of time.(7) A 2006 report by the United Nations (U.N.) revealed that raising animals for food generates more greenhouse gases than all the cars and trucks in the world combined. Senior U.N. Food and Agriculture Organization official Henning Steinfeld reported that the meat industry is “one of the most significant contributors to today’s most serious environmental problems.”