A year ago, Carlos Nobre, one of Brazil's top climate scientists, was a rare voice of optimism about the future of the planet. The 73-year-old, one of the top experts on the Amazon rainforest, was cheering the fact that "for the first time, all the leaders in the region are mobilized to find solutions for the forest" at a summit in northern Brazil. Today, he warns that the world's biggest jungle, which is being ravaged by the worst drought-fuelled wildfires in decades, is in existential danger...