If the rule survives the inevitable legal challenges, it will mark the first time the federal government limits air pollution from carbon dioxide.
Even states that sued Obama over the EPA's new rules to combat climate change are trying to figure out how to comply with them.
Somerville, Mass., is partnering with green tech companies to meet its environmental goals -- and hopefully help other cities meet theirs.
Historic snowstorms brought the city's buses and trains to a standstill for weeks. Is new leadership enough to get the agency back on track?