Agence France-Presse: The waters of Sydney Harbour plunged into darkness on Saturday night, with the iconic Opera House and Harbour Bridge killing their lights for an hour in a global call for swift action on climate change. Chatham Island, the largest of a tiny group of Pacific islands 800 kilometres (500 miles) southeast of New Zealand, unofficially began Earth Hour by switching off its diesel generators at 0645 GMT, or 8:30 pm local time. The 25-hour energy-saving marathon officially began in …