Cities that mimic forests, bricks made from converted carbon dioxide and highways lined with wind turbines powered by traffic. These are ideas that, for now, still belong to a distant, brighter future – when the world’s focus can be turned from halting runaway climate change to actually reversing it. Yet these were among the innovations showcased in a two-day Commonwealth brainstorming session in London, attended by leading climatologists. They’re the type of plans that the…