text: A small crowd cheered and applauded as the skyline went dark. The Opera House was lit in a deep shade of green to symbolise renewable energy.
  The annual event is organised by WWF, the global environment campaign.
  It encourages cities and individuals to switch off non-essential lights for an hour at 20:30 local time.
  Critics have dismissed the campaign, now into its seventh year, as a gimmick of little or no practical benefit.
  This year, Russian President Vladimir Putin is taking part for the first time.
  The Kremlin due to switch off its lights at 16:30 GMT along with 90 other landmark buildings in Moscow.
  Sydney cut its lights at 09:30 GMT.
  "It's really exciting," local resident Jessica Bellamy told AFP news agency.
  "It's been a very inspiring night because it's all about hope and change."
  One person wrote on Twitter: "Sydney Harbour bridge is in darkness for Earth Hour. You can even see the stars!"
target: Australia's biggest city, Sydney, has switched off its lights for an hour as the Earth Day climate change protest gets under way across the globe.