Cities in Asia and the United States emit the most heat-trapping gas that feeds climate change, with Shanghai the most polluting, according to new data that combines observations and artificial intelligence. Seven states or provinces spew more than 1 billion metric tons of greenhouse gases, all of them in China, except Texas, which ranks sixth, according to new data from an organization co-founded by former U.S. Vice President Al Gore and released Friday at the United Nations climate talks in Baku, Azerbaijan.