Top 20 Cities with Billions at Risk from Climate Change

By 2050, more than 6 billion humans are expected to live in cities, according to the United Nations. Ports, which constitute more than half the world's largest cities, will face unique challenges as their populations swell.

More than 130 port cities around the world are at increasing risk from severe storm-surge flooding, damage from high storm winds, rising and warming global seas and local land subsidence. Poorly planned development often puts more people in vulnerable areas, too, increasing risk. About $3 trillion of assets are at risk today, a tally on track to reach $35 trillion by 2070, according to an ongoing study by the Organization of Economic Cooperation and Development.

Here are the 20 port cities most vulnerable to climate extremes, ranked by assets at risk.