ClimateWire: First of a three-part series. Bob Ackley may be the only person who has driven up and down every single street -- 1,500 miles total -- in Washington, D.C. While Ackley, a plain-speaking New Englander, enjoyed exploring the nation's capital, which he described as "beautiful," this was serious business. He was measuring leaks of methane, a potent greenhouse gas that is also the main component of natural gas. Measured in terms of warming the atmosphere, methane is 25 times more potent than carbon...