Australian Broadcasting Corporation: Prime Minister Julia Gillard has listed climate change as among her top three priorities, but the Opposition says it is the only major party with a clear policy. Ms Gillard has sought to gain the upper hand on climate change on the first day of the election campaign. Labor’s support dropped in the opinion polls earlier this year when it announced it was shelving the emissions trading scheme. But Ms Gillard says she will unveil new policies during the campaign. She …