Australian Prime Minister John Howard has announced a shift in policy on climate change, promising to set up a carbon trading scheme to cut pollution. Mr Howard said he would set a target next year for limiting greenhouse gas emissions and also pledged to put in place a carbon trading scheme by 2012. Australia is one of the worst polluters per head of population in the world. Despite his new plans, Mr Howard has warned that setting a cap on carbon emissions would hurt the economy. His announcement comes ahead of a national election later this year, in which Mr Howard will be seeking his fifth consecutive win. Sydney has made one of the biggest environmental statements Australia has ever seen. Parts of the country's largest city have been plunged into near darkness to raise awareness of global warming. Lights on the city's iconic coat-hanger bridge were switched off, while the famous white sails of the Opera House were darkened. Families held candle-lit picnics on the edges of Sydney harbour, while thousands of suburban homes were blacked out. "I'm feeling very happy because everyone's participating in something that is for the world," explained Mexican tourist Nayeli Dellafuente. Twelve-year-old Alex Martuccio from Sydney was also enthusiastic about the big switch-off. "Tonight's a good way to save power and to help the world be a cleaner place," he said. Hundreds of businesses joined in too. Many tower blocks have spent the evening in the dark, although there were notable exceptions.