Obama: ‘American Leadership Helped Rally the World’ on Global Warming Treaty

"We now have hope for affecting climate change and the instability that would threaten our national security. Because American leadership helped rally the world and forge its most ambitious agreement in history to fight climate change. (Applause) So, if we are going to cease the possibilities of our time, we have to use all of these tools. And we have to have the courage to try new paths."