Honda Motor Co. has begun commercial production of its new zero-emission, hydrogen fuel cell car, called the FCX Clarity. The midsize four-seat sedan, which runs on hydrogen and electricity, emits only wator vapor and none of the gases believed to be responsible for global warming. Honda says the vehicle offers two times better fuel efficiency than a gas-electric hybrid and three times that of a traditional gasoline-powered vehicle. The car will initially be available for lease starting July to a limited number of customers in southern California and then in Japan later this year. Honda says it expects to lease a few dozen units in the U.S. and Japan within a year, and about 200 units within three years. One of the biggest obstacles standing in the way of wider adoption of fuel cell vehicles is cost and the lack of hydrogen fueling stations.