New Scientist: The US has just taken its first significant step towards cutting its greenhouse gas emissions. It has set targets to cut carbon emission from existing power plants. Forget all the gobbledegook: we'll explain what today's announcement really means. Sorry, what has happened? Last year, US president Barack Obama asked the Environmental Protection Agency (EPA) to come up with a plan to cut carbon dioxide emissions from existing power plants. The agency has just presented that plan. It says that by...