As I type these words, I'm flying 39,000 feet over Ecuador. Shortly, I will land in Lima, a sprawling city of about nine million people. Lima is one of the cities of the world most immediately threatened by global warming. The city was built on the edge of a desert, one of the driest in the world. And its primary source of water is a small river, the Rimac. The Rimac's water trickles of glaciers high in the Andes which, unfortunately for Limeños, are rapidly melting. Peru has lost about 30 percent of its glacial ice in the last 40 years [...]