On September 23, the United Nations will open its Climate Action Summit here in New York, three days after the Global Climate Strike, led by Greta Thunberg, will sweep through thousands of cities worldwide. To mark the occasion, Intelligencer will be publishing “State of the World,” a series of in-depth interviews with climate leaders from Bill Gates to Naomi Klein and Rhiana Gunn-Wright to William Nordhaus, interrogating just how they see the precarious climate future of the planet — and just how hopeful they think we should all be about avoiding catastrophic warming. (Unfortunately, very few are hopeful.)