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The defiant ones have come to California. Of course they have. Where else would they go?

Mayors, governors, corporate executives and environmental activists from four continents are gathering in San Francisco this week to show what they can do to stave off the most catastrophic effects of climate change, even if the president of the world’s most powerful country — the United States, which is also history’s biggest polluter — won’t.

It’s a gamble. As my colleague Brad Plumer writes, these defiant ones are trying to demonstrate that they can take big steps to cut the greenhouse gas emissions that have warmed the atmosphere since the beginning of the industrial age. But their efforts have not been enough to offset the effects of the Trump administration’s rollbacks on climate policy. And the world as a whole is nowhere close to meeting the targets set under the Paris climate accord three years ago, an accord that President Trump intends to withdraw the United States from.

California is not just where some of the consequences of climate change are being felt acutely, nor simply a place where high-profile solutions are being tested out. It has also been a finger in the eye of the Trump administration on climate policy; for instance, it has challenged his rollbacks on fuel-efficiency standards.