Independent: We are living through two great meltdowns — the credit crunch, and the climate crunch. The heating of the planet is now happening so fast it’s hard to pluck a single event to fix on, but here’s one. By the summer of 2013, the Arctic will be free of ice. How big an event it this? The Wall Street Crash hadn’t happened for 80 years. The Arctic Crash hasn’t happened for three million years: that’s the last time there was watery emptiness at the top of the world. The Arctic is often …