Despite the Obama Administration's emphasis on coal power plants, only one-third of the nation's greenhouse emissions come from this source. Transportation contributes an almost equal amount and industry adds another one-fifth. The big surprise is agriculture, which adds 10 percent. Australia found this out recently when it imposed a carbon tax and found it was having a big impact on farmers. It was quickly repealed. Since any big initiative against coal will have only a marginal effect on one-third of the nation's emissions, progress is likely to be slow.