Earth Hour is organized by WWF. With almost 5 million supporters and a global network in over 100 countries, it's one of the world's largest and most respected independent conservation organizations. WWF's mission   is to stop the degradation   of the Earth's natural environment and build a future where people live in harmony with nature. Earth Hour started on March 31st, in 2007 in Sydney, Australia when 2.2 million individuals and more than 2,000 businesses turned their lights off for one hour to take a stand against climate change. Only a year later Earth Hour had become a global movement with more than 50 million people across 35 countries participating. Global landmarks such as the Sydney Harbour Bridge, CN Tower in Toronto, Golden Gate Bridge in San Francisco, and Rome's Colosseum, all stood in darkness, as symbols of hope for a cause that grows more urgent by the hour. In March 2009, hundreds of millions of people took part in the third Earth Hour. Over 4,000 cities in 88 countries officially switched off to pledge   their support for the planet, making Earth Hour 2009 the world's largest movement to stop global climate change. On Saturday 27 March, Earth Hour 2010 became the biggest Earth Hour ever. A record 128 countries and territories joined the global display of climate action. Iconic buildings and landmarks from Asia Pacific to Europe and Africa to the Americas switched off. People across the world from all walks of life turned off their lights and came together in celebration and contemplation of the one thing we all have in common--our planet.   Earth Hour will continue to be a call to action to every individual, a call to stand up, to take responsibility and lead the global journey to a sustainable   future. The purpose of the text is to   _  .
tell us what WWF does advise us to take part in Earth Hour introduce the movement, Earth Hour, to us persuade us to take action to stop climate change