Photo taken on March 23, 2013 shows landmark Grand Place in Brussels, capital of Belgium, turns off its lights to mark the annual "Earth Hour" event. (Xinhua/Yan Ting)

Photo taken on March 23, 2013 shows landmark Grand Place in Brussels, capital of Belgium, before turning off its lights to mark the annual "Earth Hour" event. (Xinhua/Yan Ting)

Photo taken on March 23, 2013 shows landmark Atomium in Brussels, capital of Belgium, before turning off its lights to mark the annual "Earth Hour" event. (Xinhua/Wang Xiaojun)

Photo taken on March 23, 2013 shows landmark Atomium in Brussels, capital of Belgium, turns off its lights to mark the annual "Earth Hour" event. (Xinhua/Wang Xiaojun)

Palestinians gather around candles to mark the "Earth Hour" near the Church of Nativity in the West Bank city of Bethlehem on March 23, 2013. (Xinhua/Luay Sababa)

Palestinians gather around candles to mark the "Earth Hour" near the Church of Nativity in the West Bank city of Bethlehem on March 23, 2013. (Xinhua/Luay Sababa)

Palestinians gather around candles to mark the "Earth Hour" near the Church of Nativity in the West Bank city of Bethlehem on March 23, 2013. (Xinhua/Luay Sababa)

Palestinians gather around candles to mark the "Earth Hour" near the Church of Nativity in the West Bank city of Bethlehem on March 23, 2013. (Xinhua/Luay Sababa)

Palestinians gather around candles to mark the "Earth Hour" near the Church of Nativity in the West Bank city of Bethlehem on March 23, 2013. (Xinhua/Luay Sababa)

The Galata Tower turns off the lights to mark the annual "Earth Hour" event in Istanbul of Turkey on March 23, 2013. (Xinhua/Ma Yan)

The Bosporus Bridge turns off the lights to mark the annual "Earth Hour" event in Istanbul of Turkey on March 23, 2013. (Xinhua/Ma Yan)

Photo taken on March 23, 2013 shows the Haghia Sophia museum in Istanbul of Turkey turning off its lights to mark the annual "Earth Hour" event. (Xinhua/Ma Yan)

The Galata Tower turns on the lights after the annual "Earth Hour" event in Istanbul of Turkey on March 23, 2013. (Xinhua/Ma Yan)

The Bosporus Bridge turns on the lights before "Earth Hour" in Istanbul of Turkey on March 23, 2013. (Xinhua/Ma Yan)