The United Nations describes Iraq as the fifth-most-vulnerable country to climate change. Temperatures have increased by 1.8 degrees Celsius (3.2 degrees Fahrenheit) in three decades, according to Berkeley Earth, well above the global average, and in the summers, the mercury now regularly hits 50 Celsius (122 Fahrenheit). The heat is burning crops and desiccating marshes. As upstream dams in Turkey and Iran weaken the flows of the Tigris and Euphrates rivers, a salty tide is creeping north from the Persian Gulf, poisoning the land — and the jobs it once created.