Spend an hour calling attention to climate change this Saturday. Earth Hour is 8: 30 to 9: 30 p.m., March 31. Participants are asked to switch off their lights to mark the occasion. In 2011, more than 5,200 cities and towns in 135 counties took part in the global environmental initiative. Check out the World Wildlife Fund Canada website at earthhour. wwf.ca for more information about the event and how to join Team Earth Hour.