The lights are being switched off around the world at 8:30 p.m. on Saturday evening, to mark the 10th annual Earth Hour, and to draw attention to climate change. The initiative began in Australia in 2007 as a grass roots gesture by the World Wildlife Fund (WWF) Australia against man-made carbon dioxide emissions linked to a warming planet. In 2017, it will involve the switching off of electric lights for an hour in 7,000 cities across 172 countries, at 8:30 p.m.