Environment 360: The days of freely dumping greenhouse gases into the atmosphere are coming to an end, but how best to price carbon emissions remains in dispute. As the U.S. Congress debates the issue, Yale Environment 360 asked eight experts to discuss the merits of a cap-and-trade system versus a carbon tax. A broad spectrum of people concerned about global warming and U.S. energy independence agree on one basic truth: Sooner or later, emitting planet-warming greenhouse gases is no longer going to …