On September 27, at the request of the young people who have been staging school strikes around the world, we’re walking out of our workplaces and homes to spend the day demanding action on the climate crisis, the greatest existential threat that all of us face. It’s a one-day climate strike, if you will—and it will not be the last. This is going to be the beginning of a week of action all over the world.

A year ago, inspired by Greta Thunberg, young people around the world began ‘climate-striking’ — walking out of school for a few hours on Fridays to demand action against global warming. In March, when 1.4 million kids around the world walked out of school, they asked for adults to join them next time. That next time is Sept. 20 (in Canada and a few other countries on Sept. 27) and it is shaping up to be the biggest day of climate action in the planet’s history.

Imagine a world in which the tortured politics of the Middle East weren’t magnified in importance by the value of the hydrocarbons beneath its sands. And imagine a world in which the greatest driver of climate change—the unrelenting political power of the fossil-fuel industry—had begun to shrink. The question, of course, is whether we can reach that new world in time.

That’s right: If we’re serious about preventing catastrophic warming, the new study shows, we can’t dig any new coal mines, drill any new fields, build any more pipelines. Not a single one. We’re done expanding the fossil fuel frontier. Our only hope is a swift, managed decline in the production of all carbon-based energy from the fields we’ve already put in production.