In U.S. News & World Report, I have a new article looking at growing optimism that an emissions-reduction deal will be reached by international negotiators in Paris in November–December 2015. While many commentators have noted that the voluntary nature of the future agreement is preferable to an attempt at a legally binding deal, there is another factor at play. The fact is that the constellation of action taken by non- and sub-state actors (states/provinces, businesses, and cities) since the failure of a deal in 2009 will serve as a critical adjunct to actions by states. These initiatives will provide a well of new ideas, financing, and prodding ambition that is much more likely to put us on a path toward averting the worst effects of climate change:

Of course, these actions are still secondary to what nation-states decide to do. Only they have the legal and regulatory authority to push the economy-wide changes necessary to aggressively address climate change. The ambition and scope of those changes, however, cannot help but be improved by the wider context of action being taken by cities, businesses and other non- and sub-state actors. As the risks from climate change become more widely perceived, they should continue to serve as a useful adjunct to more robust action by nation-states, ensuring brighter prospects for a useful agreement coming out of Paris.