King supports action to combat climate change and carries a laminated graph of increases in carbon dioxide in Earth's atmosphere to respond to climate change denialists. He was the only member of Congress to join a three-day U.S. Coast Guard fact-finding mission to Greenland in 2016, where he witnessed melting ice sheets firsthand and said that the impacts of climate change were "amazing and scary." In March 2019 King joined Senate Republicans and voted in opposition to the Green New Deal.