(CNN)Tonight, for the 15th consecutive year, people around the world will turn off their lights for one hour. It's part of a grassroots global campaign called Earth Hour.
What is Earth Hour?
Earth Hour is an annual tradition started by the World Wildlife Fund (WWF) in 2007 in Sydney, Australia, to raise awareness about climate change. Participants in more than 190 countries will turn off their lights for one hour on Saturday.
Global landmarks -- including the Sydney Opera House, the Gateway of India, the Beijing Phoenix Center in China, the Brandenburg Gate in Germany, the Colosseum in Italy, the Empire State Building in the United States and Christ the Redeemer in Brazil -- will turn off their lights to show support for the campaign.
What is the purpose of Earth Hour?
WWF describes the event as a symbol of "unity" and "hope" for a sustainable future.
"Earth Hour aims to increase awareness and spark global conversations on protecting nature, tackling the climate crisis, and working together to shape a brighter future for us all," the WWF says on the Earth Hour website.
The Earth Hour campaign has led to other actions related to curbing climate change. The WWF's chapter in Uganda, for instance, created the first "Earth Hour Forest" in 2013. Also, Argentina used its 2013 Earth Hour campaign to help pass a Senate bill for a 3.4 million hectares (8.4 million acres) Marine Protected Area in the country, according to the WWF.
How can I participate?
You can mark Earth Hour by turning off your lights from 8:30 to 9:30 p.m. in your local time zone.
The official Earth Hour website suggests seven ways that supporters can spend their lights-off hour, including reconnecting with nature and attending local Earth Hour events in their communities.
The WWF also recommends that supporters "take action beyond the hour, whether it is supporting a local WWF project or getting involved in Earth Hour campaigns in their own country, or starting the movement in their own community."