One controversial environmental sustainability issue has to do with using carbon pricing as a means of reducing greenhouse gases. In this university podcast, Harvard professor Robert Stavins lays out two instruments for carbon pricing: taxing CO2 emissions and issuing tradable carbon permits that major league polluters must buy for each ton of CO2 they send into the atmosphere, also known as “cap and trade.” He explains the ins and outs and pros and cons of both. Stavins was talking at the 2010 Climate Policy Instruments in the Real World conference, an event convened by the Program on Energy and Sustainable Development (PESD) at Stanford University