"The best thing we can do in an effort to try to change people's thinking is to do this mandatory reporting requirement," Kerry said. "The mandatory reporting requirement has to be updated every five years. Every five years, it is mandatory that countries retool their reduction levels in order to meet the demands of meeting the curve of reduction to which they have committed. So that is a serious form of enforcement, if you will, compliance. But there is no penalty for it, obviously, but if there had been a penalty, we wouldn't have been able to get an agreement."