Xi Jinping, China's president, right, and U.S. President Barack Obama, stand during a state visit arrival ceremony on the South Lawn of the White House in Washington, D.C., U.S., on Friday, Sept. 25, 2015. China will start a national pollution-trading system to cut global warming emissions and make a substantial financial commitment to help poorer countries move away from fossil fuels, two U.S. officials said yesterday. Photographer: Andrew Harrer/Bloomberg via Getty Images
