Landmark buildings around the world switched their lights off for one hour on Saturday 23 March to mark Earth Hour, a campaign to highlight the problem of climate change.

Earth Hour started in Sydney in 2007, when 2.2 million people turned off all non-essential lights for an hour. The next year was an even bigger event as major cities around the world followed Sydney's lead and turned off their lights for an hour to raise awareness about the need to take action on climate change.

Earth Hour, organised by the World Wide Fund for Nature (WWF), has since snowballed into a global event.

This year, key landmarks around the world such as the Sydney Opera House and Harbour Bridge, the Petronas towers in Malaysia, the UK parliament and Buckingham Palace and the Empire State Building all took part.

(Courtesy: DanaeYiakkoupi, YouTube)

In the UK, Earth Hour ambassador, pop group McFly gave a live acoustic performance in panda onesies to kickstart the event. Celebrity chefs Gordon Ramsay and Raymond Blanc came out with special recipes for families to prepare and eat by the candlelight. WWF roped in Kevin McCloud, Miranda Richardson and Alistair McGowan to record Rudyard Kipling's famous Just So stories.

Besides the Empire State Building in New York, the US will mark the occasion by switching off the glitzy lights of the Las Vegas strip, Los Angeles Airport and Niagara Falls.