Houses across the world are switching off their lights for one hour at 8 p.m., on Saturday, March 29, to make a statement about the greatest factor of global warming – coal-fired electricity.

The Earth Hour is a project started last year by the World Wildlife Federation.

"It's largely symbolic," said Monica Echeverria, a spokeswoman for the World Wildlife Federation, according to the Los Angeles Times. "The purpose is to keep getting the word out about how important it is to reduce energy and carbon emissions. It's all about climate change."

The Earth Hour project aims to make people more aware about the consequences of global warming and make them feel like they are working together as a team, to save the health of our planet. The WWF hopes that the participants will think of changing the light bulbs in their homes with compact fluorescents, which are much more economical and efficient.

The global warming issue is one of the most difficult challenges Earth faces, and it can only be solved if a large number of people work together, trying to change something.

On the project’s website, www.earthhour.org, WWF informs that on March 31 2007, when Earth Hour started in Australia, over 2.2 million Sydney residents and over 2,100 businesses turned off the lights for one hour, resulting in a 10.2 percent energy reduction across the city.

This year, Earth Hour spread all around the globe and 24 important cities in the world are expected to participate in the action on March 29, at 8 p.m.