ClimateWire: Mayor Harvey Hall can get very excited about efforts to “decarbonize” California’s energy system. His city is the hub of Kern County. Its two major businesses, agriculture and oil, are in a severe slump. Unemployment is running about 17 percent. “I’ve lived here all my life,” explains Hall, 69. “This economy is probably the worst that I’ve ever seen.” So when BP PLC and Rio Tinto, the big British-Australian mining company, decided on a Kern County site to build the nation’s …