By the time the landmark Paris agreement was ratified in 2015, climate change was one of the rare issues on which China and the United States — the world’s No. 1 and No. 2 polluters, respectively — could find common purpose. This shared purpose was dealt a serious setback when the Trump administration backed out from the Paris climate accord. Enter California, the stubborn state that has joined China in its quest to curb global warming. Take a look here how the unlikely duo is collaborating to fight against climate change.