Lights out as world observes Earth Hour

Sydney's iconic Opera House and Harbour Bridge went dark yesterday at the start of Earth Hour, followed by cities across Asia in a global switch-off aimed at revitalising efforts against climate change. The WWF-run event is supported by 4,000 cities in a record 125 countries and includes 1,200 landmarks from the Forbidden City to the pyramids.

"From Brazil to America, to Canada, all the way down to Australia, Japan and India – it's a really diverse set of countries taking part this year," Earth Hour Executive Director Andy Ridley said.

Sydney's buildings plunged into gloom at 8.30pm, setting off a rolling wave of darkness that spread across Japan, Hong Kong, China, Indonesia and India and will sweep the globe in a boost for the environment.