What does the activity warn against?

International landmarks, from Sydney’s Opera House to the Forbidden City in China and to Buckingham Palace in London, will be plunged into darkness Saturday. This campaign has renewed their efforts to highlight the dangers of climate change. Millions of homes in 125 countries are also expected to take part by switching off their lights for 60 minutes in a show of global solidarity. The event in its fourth year has the support of the United Nations Secretary General Ban Ki-Moon, who said it was both a warning and a beacon of hope. Earth Hour was the idea of activists of the World Wildlife Fund for Nature in Australia. The first community to switch off their lights in Earth Hour 2010 was the Chatham Islands, eight hundred kilometers east of New Zealand. The wave of darkness will roll across Asia to the Middle East, Europe.