Sydney’s iconic Harbour Bridge and Opera House temporarily went dark on Saturday as nations across the western Pacific turned out the lights for Earth Hour 2010 to call for action on climate change.

The symbolic one-hour switch-off, first held in Sydney in 2007, has become an annual global event and organizers World Wide Fund for Nature (WWF) said they expect this year’s to be the biggest so far.

The remote Chatham Islands was the first of more than 100 nations and territories to turn off the power at 8.30 p.m. local time, in a rolling event around the globe that ends just across the International Dateline in Samoa 24 hours later.