BBC: Delegates from 192 countries are gathering in the Danish capital Copenhagen for the opening of the long-awaited UN summit on climate change. The conference has been described by some scientists as the most important the world has ever seen. Security is tight as organisers expect 15,000 delegates and 100 world leaders to attend over the next two weeks. On the eve of the summit, the UN’s chief climate negotiator Yvo de Boer said the talks were in excellent shape. He …