Agence France-Presse: Sydney’s iconic Opera House and Harbour Bridge went dark along with millions of homes Saturday at the start of Earth Hour, a global switch-off aimed at revitalising efforts against climate change. Harbour ferry horns blared to signal the energy-saving event, which is supported by 4,000 cities in a record 125 countries and includes 1,200 famous landmarks from the Forbidden City to the pyramids to the Las Vegas Strip. “From Brazil to America, to Canada, all the way down to …