As the world debates how to deal with the mounting impacts of climate change, consensus has been hard to find. But Shindell, an atmospheric scientist who studies ways to identify and mitigate climate threats, believes there’s a promising path toward immediate action – and it starts with methane. A greenhouse gas emitted by livestock and garbage, methane is one of the significant drivers of global warming, but it gets comparatively less attention than, say, carbon dioxide. Shindell, who chaired a United Nations global methane assessment, argues that steps to reduce methane emissions are less expensive and can result in more immediate improvements to air quality and public health. Policymakers and environmentalists are listening: More than 125 countries have pledged to reduce methane emissions by 30 percent before the end of the decade.