The WWF's Earth Hour is upon us again. Tommorrow, at 8.30pm local time people, businesses and iconic buildings around the world will be switching off their lights for an hour to "make a statement to the world’s governments for more urgent and effective action on climate change". Last year, Google went black. The year before, 2.2 million people in Sydney cut the city's mains electricity consumption by upto 10%. I've no idea whether initiatives like this make a real difference. But the issue is important enough to be worth a try. So I'll be doing it. You can find out more, and sign up here.