(To get this story in your inbox, subscribe to the TIME CO2 Leadership Report newsletter here.) U.S. climate envoy John Kerry visited China this week to jumpstart climate discussions between the world’s two largest economies and greenhouse gas emitters amid a period of serious tension between the two countries. To longtime followers of the ins and outs of climate policy, the trip was an important stop on the trudge to the United Nations climate conference to be held in Dubai this fall.