Agence France-Presse: Millions of people from Sydney to Sweden are set to switch off their lights on March 27, as part of the global ‘Earth Hour’ campaign to highlight climate change, organisers said Sunday. Some 250 cities around the world have already signed up for the symbolic, energy saving exercise which in 2009 saw landmarks such as the Sydney Harbour Bridge and New York’s Empire State Building plunged into darkness. “The event will be held at 8:30 pm Saturday 27 March in cities and towns all …