Whenever the causes of climate change are discussed, fossil fuels top the list.Oil, natural gas, and especially coal are indeed major sources of human-caused emissions of carbon dioxide (CO2) and other greenhouse gases (GHGs). But we believe that the life cycle and supply chain of domesticated animals raised for food have been vastly underestimated as a source of GHGs, and in fact account for at least half of all human-caused GHGs.