April 28, 2016 — When the world’s poor countries demanded action during the failing United Nations–led climate negotiations in Copenhagen in 2009, the U.S. government responded with a promise: It would help raise US$100 billion a year by 2020 to assist efforts to cope with climate change in the global south.

Out of that commitment has slowly grown a peculiar but potentially important institution known as the Green Climate Fund. The fund has nowhere near US$100 billion to spend, but, if all goes according to plan, it will deliver significant aid to impoverished nations that are threatened by a warming planet.

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