China and the U.S. are by far two of the biggest carbon dioxide emitters in the world. U.S. climate envoy John Kerry arrived in Shanghai on the evening of April 14 to discuss cooperation between the two sides on climate change. Professor Guan Dabo from the Department of Earth System Science at Tsinghua University shares his insights on this issue. He says that climate change requires the efforts of every nation. China and U.S. should work together to mitigate climate change impact.