Govt buildings to mark Earth Hour

The lights will go off at Government buildings, Leinster House, the Customs House and the Four Courts at 8.30pm tonight to mark Earth Hour.

Up to 4,000 cities across the world are taking part in the attempt to demonstrate support for action on climate change.

Two of Sydney's famous landmarks had been plunged into darkness.

The city's Harbour Bridge and Opera House turned off the lights to mark Earth Hour to raise awareness about climate change.

As the clock strikes 8.30pm around the globe other famous structures, including the Notre Dame cathedral in Paris and Big Ben in London, will follow suit.

Households across Ireland are being encouraged to switch off their lights also to conserve energy.