The suit follows up on the EPA's allegations that VW installed illegal software to cheat on emissions tests.
Here are five of the biggest climate milestones of the year.
Ride-sharing is catching on around the world, but still lagging in the U.S.
From tanking startups to banning tips, from seafood-prepping slaves to climate-protecting seaweed, these works of food journalism brightened the year.
The repeal was a gift to the oil industry, but at least Democrats got some good stuff in return.
The Waldorf Astoria is among the hotels committed to reducing CO2 emissions by 30 percent.
These are the top stories from 2015 that actually give us hope for the future.
The mega-retailer could be getting into the cargo market to compete with UPS and FedEx.
The mansion was destroyed decades before the BP oil spill.