Marketplace: Tess Vigeland: Secretary of State Hillary Clinton is in Beijing today and through the weekend. She’s talk with Chinese leaders about how to ride out this global recession. But she also wants to tackle climate change. China and the U.S. are the world’s biggest sources of carbon emissions. From Shanghai, Marketplace’s Scott Tong reports. Scott Tong: Together, China and the U.S. exhale 40 percent of the world’s carbon. Secretary Clinton thinks the two can collaborate to reduce that …