Carefully chosen words, tedious negotiations, lines in the sand. At stake: the continued release of the greenhouse gases that contribute to global climate change. But this isn’t diplomacy at the United Nations we’re talking about, it’s San Diego politicians struggling to work together to buy and sell green energy. Last fall, the city of San Diego decided to start its own utility to buy and sell power. That’s because the city’s “climate action plan” says all electricity sold to city residents must come from renewable sources within the next two decades.