Iraq’s Mosul dam is at risk of collapse, threatening to send a bulldozer wave of water through the most populated parts of Iraq. H7N9 “bird flu” cases are surging in parts of China. Saudi military action threatens to tip millions of Yemen’s people into famine.The world is full of potential crises, and at some point in the next four years the Trump administration will be faced with a global mega-disaster that will test his presidency.