Over the years, the capital of the fight against climate change has been Kyoto, or Paris – that’s where the symbolic political agreements to try and curb the earth’s greenhouse gas emissions have been negotiated and signed. But now, New York City vaulted to leadership in the battle.

On Wednesday, its leaders, at a press conference in a neighborhood damaged over five years ago by Hurricane Sandy, announced that the city was divesting its massive pension fund from fossil fuels, and added for good measure that they were suing the five biggest oil companies for damages. Our planet’s most important city was now at war with its richest industry. And overnight, the battle to save the planet shifted from largely political to largely financial.

That shift had been under way for a long time, of course. The divestment campaign, which my organization 350.org helped launch, has become the largest of its kind in history, with now more than $6tn in endowments and portfolios divesting in part or in whole […]