Science: A coalition of 38 nations and several international groups have launched the Global Methane Initiative, accelerating shared efforts to cut pollution of a gas that accounts for about one-fifth of the warming potential of all greenhouse gases. And the climate benefits of cutting emissions of methane are more immediate: It persists in the atmosphere for a decade or so, while CO2 lasts for hundreds of years. Methane is also a more potent warmer. Scientists and advocates mostly lamented …