China Hosts U.N. Climate Change Summit

Three thousand delegates are in China for a U.N. conference on climate change.  The host nation is the world's biggest carbon emitter.  The U.S. ranks second, and the two nations combine for 40% of the worlds total emission of greenhouse gases.  Negotiators this week hope to narrow differences on curbing emissions before the major year-end meeting in Mexico.  Expectations are low this week, as last year's climate summit failed to reach an accord.