"Extraordinary, isn't it? I've been hearing all about COP," said the queen to the duchess of Cornwall. "Still don't know who is coming. … We only know about people who are not coming. … It's really irritating when they talk but they don't do." Queen Elizabeth II was expressing her exasperation at the possible number of no-shows at the U.K.'s coming climate summit in Glasgow, Scotland. Among the absentees may be Chinese President Xi Jinping, whose country generates more carbon dioxide than the U.S. and EU combined. Behind the queen's exasperation, however, lies a political reality. Nations like China are...