World leaders are meeting today in New York for a U.N. climate summit. The U.N. secretary-general convened the summit hoping to build momentum for a global agreement on climate action next year. President Barack Obama is scheduled to address the gathering this afternoon. Notably absent from the summit are the heads of state of China and India. In addition to the U.S., those nations are two of the world’s top emitters of greenhouse gases. And they’re rapidly building new coal-burning power plants — the largest contributors of carbon dioxide emissions around the world. Join Diane and her guests as they discuss the political and economic challenges of combating climate change.