What would the perfect climate-change lender look like?

IMAGINE, FOR a second, that you are a guest at the Mount Washington Hotel in the ski resort of Bretton Woods, New Hampshire. You have arrived to enjoy neither the slopes nor the hotel’s 18-hole golf course. Instead, you are here for the sort of conference that reimagined the international financial system at the end of the second world war. This time there is a green twist. Your job is to give the Bretton Woods twins—the IMF and the World Bank—a sister in the form of a perfect climate-change lender.

According to Nicholas Stern and Vera Songwe, two economists, by 2030 poor countries will need somewhere in the region of $2trn-$2.8trn a year of investment to combat climate change. The Climate Policy Initiative, a think-tank, estimates that in 2021 total climate investments, in both rich and poor countries, amounted to $650bn. In the catchphrase of the climate-change world, the financial system needs to “turn billions into trillions”. Getting these funds to flow, somehow, is the mission of your new Green Bank.

The first question is a vexed one: who coughs up to pay for the lender? The struggle to create a climate-finance framework started at the so-called Earth Summit in 1992. The summit…