Earth hour has grown from just one city - an estimated 2.2 million people participated in Sydney in 2007 - to 50 million people in 400 cities around the world in 2008 and even more in 2009. In 2010 more than 1,000 cities and towns in 120 countries around the world will, at 8.30pm on Saturday, March 27 turn off the lights for Earth Hour. It is a symbolic event that has been tirelessly promoted by the WWF to promote action on climate change. While its impact by itself is somewhat negligible, although there is a noticeable power use reduction for the hour, it has increased general public awareness of energy use and it's contribution to climate change.
Related: Greenpeace report: Dealing in Doubt