US President Barack Obama smiles during the opening ceremony of the G20 Summit in Hangzhou on September 4, 2016. G20 leaders confront a sluggish global economy and the winds of populism as they open annual talks, but the long war in Syria and the South China Sea territorial dispute hang over the summit. / AFP PHOTO / POOL / Mark SchiefelbeinMARK SCHIEFELBEIN/AFP/Getty Images