One day, five years ago, Luciano Lliuya sat talking with a friend about the many changes and costs that climate change is bringing to the Andes, whose residents have, by global standards, done very little to contribute to the problem. “We wondered,” he said, “whether we could find los responsables” — the responsible ones — and somehow persuade them to change their behavior. He wanted, fervently, to find a way to stop the ice from melting even more. Luciano Lliuya’s friend introduced him to a contact at a nongovernment organization called Germanwatch, based in Bonn, that works to promote equity...