U.S. Special Envoy for Climate John Kerry has wrapped up his four-day visit to China. Kerry met with senior Chinese officials to discuss how the U.S. and China could improve cooperation to address climate change. How much progress has been made during the long hours of discussion? Can the two sides manage to cooperate amidst the current chilly China-U.S. relations? And what can the world's two largest economies contribute to tackling this challenge to mankind?