The United Nations will participate in Earth Hour on Saturday by turning off the lights at its offices around the world for one hour, UN spokesman Martin Nesirky announced here Friday.

"Joining the millions of people around the world who observe Earth Hour, the secretary-general said that the United Nations will participate with a determination to take action on climate change," Nesirky said at a daily news briefing here, referring to UN chief Ban Ki-moon.

Ban "said that governments, business and civil society all have a role to play in coming up with common sense answers for a cleaner, greener world," the spokesman said.

Earth Hour, launched in 2007 in Australia by the World Wide Fund for Nature (WWF), a global conservation group, calls on people, organizations and cities to turn off their non-essential lights for one hour starting at 8:30 p.m. local time.

This is the fourth year that the United Nations joins hundreds of millions of people around the world in switching off the lights.

The Earth Hour event takes place roughly one week after the vernal equinox -- when night and day are of the same duration in both hemispheres, ensuring that it will be dark everywhere in the world at 8:30 in the evening.