Hundreds of millions of people, businesses and governments around the world unite each year to support the largest environmental event in history - Earth Hour.
Watch on YouTube
On Saturday March 31 2012 at 8.30pm hundreds of millions of global citizens from 100 different countries will unite in the action of lights out. Will you be one of them?
More than 5,200 cities and towns in 135 countries worldwide switched off their lights for Earth Hour 2011 alone, sending a powerful message for action on climate change