Mongabay: An ongoing methane gas leak at a facility in Southern California whats been called the nations biggest environmental disaster since the BP oil spill has officially been declared an emergency by Governor Jerry Brown. Natural gas, or methane, first started leaking from Southern California Gas Co.s Aliso Canyon storage facility on October 23 last year. Some 2,300 homes have been evacuated in nearby Porter Ranch, a neighborhood of Los Angeles, after residents began experiencing nosebleeds,...