Guardian: The United States and China, the worlds biggest emitters of greenhouse gases, have announced they will formally ratify the Paris climate change agreement in a move campaigners immediately hailed as a significant advance in the battle against global warming. Speaking on Saturday, on the eve of the G20 summit in Hangzhou, US president, Barack Obama, confirmed the long-awaited move, the result of weeks of intense negotiations by Chinese and American officials. Just as I believe the Paris agreement...