Around the world, governments and automakers are promoting electric vehicles as a key technology to curb oil use and fight climate change. General Motors has said it aims to stop selling new gasoline-powered cars and light trucks by 2035 and will pivot to battery-powered models. This week, Volvo said it would move even faster and introduce an all-electric lineup by 2030. But as electric cars and trucks go mainstream, they have faced a persistent question: Are they really as green as advertised? While experts broadly agree that plug-in vehicles are a more climate-friendly option than traditional vehicles, they can still have their own environmental impacts, depending on how they’re charged up and manufactured. Here’s a guide to some of the biggest worries — and how they might be addressed.